NCERT- Complete Geography

C ONTENTS FOREWORD

iii

UNIT I : GEOGRAPHY 1.

AS A

DISCIPLINE

Geography as a Discipline

UNIT II : THE EARTH

1-12 2 13-38

2.

The Origin and Evolution of the Earth

14

3.

Interior of the Earth

21

4.

Distribution of Oceans and Continents

30 39-74

UNIT III : LANDFORMS 5.

Minerals and Rocks

40

6.

Geomorphic Processes

45

7.

Landforms and their Evolution

58 75-110

UNIT IV : CLIMATE 8.

Composition and Structure of Atmosphere

76

9.

Solar Radiation, Heat Balance and Temperature

79

10.

Atmospheric Circulation and Weather Systems

88

11.

Water in the Atmosphere

98

12.

World Climate and Climate Change

UNIT V : WATER (OCEANS)

103 111-125

13.

Water (Oceans)

112

14.

Movements of Ocean Water

120

UNIT VI : LIFE

ON THE

EARTH

126-140

15.

Life on the Earth

127

16.

Biodiversity and Conservation

135

GLOSSARY

141-144

UNIT I GEOGRAPHY AS A DISCIPLINE This unit deals with •

Geography as an integrating discipline; as a science of spatial attributes

•

Branches of geography; importance of physical geography

CHAPTER

GEOGRAPHY

Y

ou have studied geography as one of the components of your social studies course upto the secondary stage. You are already aware of some of the phenomena of geographical nature in the world and its different parts. Now, you will study ‘Geography’ as an independent subject and learn about the physical environment of the earth, human activities and their interactive relationships. Therefore, a pertinent question you can ask at this stage is — Why should we study geography? We live on the surface of the earth. Our lives are affected by our surroundings in many ways. We depend on the resources to sustain ourselves in the surrounding areas. Primitive societies subsisted on ‘natural means of subsistence’, i.e. edible plants and animals. With the passage of time, we developed technologies and started producing our food using natural resources such as land, soil and water. We adjusted our food habits and clothing according to the prevailing weather conditions. There are variations in the natural resource base, technological development, adaptation with and modification of physical environment, social organisations and cultural development. As a student of geography, you should be curious to know about all the phenomena which vary over space. You learn about the diverse lands and people. You should also be interested in understanding the changes which have taken place over time. Geography equips you to appreciate diversity and investigate into the causes responsible for creating such variations over time and space. You will develop skills to understand the globe converted into maps and have a visual sense

AS A

DISCIPLINE

of the earth’s surface. The understanding and the skills obtained in modern scientific techniques such as GIS and computer cartography equip you to meaningfully contribute to the national endeavour for development. Now the next question which you may like to ask is — What is geography? You know that earth is our home. It is also the home of many other creatures, big and small, which live on the earth and sustain. The earth’s surface is not uniform. It has variations in its physical features. There are mountains, hills, valleys, plains, plateaus, oceans, lakes, deserts and wilderness. There are variations in its social and cultural features too. There are villages, cities, roads, railways, ports, markets and many other elements created by human beings across the entire period of their cultural development. This variation provides a clue to the understanding of the relationship between the physical environment and social/cultural features. The physical environment has provided the stage, on which human societies enacted the drama of their creative skills with the tools and techniques which they invented and evolved in the process of their cultural development. Now, you should be able to attempt the answer of the question posed earlier as to “What is geography”? In very simple words, it can be said that geography is the description of the earth. The term geography was first coined by Eratosthenese, a Greek scholar (276-194 BC.). The word has been derived from two roots from Greek language geo (earth) and graphos (description).

GEOGRAPHY AS A DISCIPLINE

Put together, they mean description of the earth. The earth has always been seen as the abode of human beings and thus, scholars defined geography as, “the description of the earth as the abode of human beings”. You are aware of the fact that reality is always multifaceted and the ‘earth’ is also multi-dimensional, that is why many disciplines from natural sciences such as geology, pedology, oceanography, botany, zoology and meteorology and a number of sister disciplines in social sciences such as economics, history, sociology, political science, anthropology, etc. study different aspects of the earth’s surface. Geography is different from other sciences in its subject matter and methodology but at the same time, it is closely related to other disciplines. Geography derives its data base from all the natural and social sciences and attempts their synthesis. We have noted that there exist variations over the surface of the earth in its physical as well as cultural environment. A number of phenomena are similar and many are dissimilar. It was, therefore, logical to perceive geography as the study of areal differentiation. Thus, geography was perceived to study all those phenomena which vary over space. Geographers do not study only the variations in the phenomena over the earth’s surface (space) but also study the associations with the other factors which cause these variations. For example, cropping patterns differ from region to region but this variation in cropping pattern, as a phenomenon, is related to variations in soils, climates, demands in the market, capacity of the farmer to invest and technological inputs available to her/him. Thus, the concern of geography is to find out the causal relationship between any two phenomena or between more than one phenomenon. A geographer explains the phenomena in a frame of cause and effect relationship, as it does not only help in interpretation but also foresees the phenomena in future. The geographical phenomena, both the physical and human, are not static but highly dynamic. They change over time as a result of the interactive processes between ever

3

changing earth and untiring and ever-active human beings. Primitive human societies were directly dependent on their immediate environment. Geography, thus, is concerned with the study of Nature and Human interactions as an integrated whole. ‘Human’ is an integral part of ‘nature’ and ‘nature’ has the imprints of ‘human’. ‘Nature’ has influenced different aspects of human life. Its imprints can be noticed on food, clothing, shelter and occupation. Human beings have come to terms with nature through adaptation and modification. As you already know, the present society has passed the stage of primitive societies, which were directly dependent on their immediate physical environment for sustenance. Present societies have modified their natural environment by inventing and using technology and thus, have expanded the horizon of their operation by appropriating and utilising the resources provided by nature. With the gradual development of technology, human beings were able to loosen the shackles of their physical environment. Technology helped in reducing the harshness of labour, increased labour efficiency and provided leisure to human beings to attend to the higher needs of life. It also increased the scale of production and the mobility of labour. The interaction between the physical environment and human beings has been very succinctly described by a poet in the following dialogue between ‘human’ and ‘nature’ (God). You created the soil, I created the cup, you created night, I created the lamp. You created wilderness, hilly terrains and deserts; I created flower beds and gardens. Human beings have claimed their contribution using natural resources. With the help of technology, human beings moved from the stage of necessity to a stage of freedom. They have put their imprints everywhere and created new possibilities in collaboration with nature. Thus, we now find humanised nature and naturalised human beings and geography studies this interactive relationship. The space got organised with the help of the means of transportation and communication network. The links (routes) and nodes (settlements of all types and hierarchies) integrated the space and

4

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

gradually, it got organised. As a social science discipline, geography studies the ‘spatial organisation’ and ‘spatial integration’. Geography as a discipline is concerned with three sets of questions: (i) Some questions are related to the identification of the patterns of natural and cultural features as found over the surface of the earth. These are the questions about what? (ii) Some questions are related to the distribution of the natural and human/ cultural features over the surface of the earth. These are the questions about where? Taken together, both these questions take care of distributional and locational aspects of the natural and cultural features. These questions provided inventorised information of what features and where located. It was a very popular approach during the colonial period. These two questions did not make geography a scientific discipline till the third question was added. The third question is related to the explanation or the causal relationships between features and the processes and phenomena. This aspect of geography is related to the question, why? Geography as a discipline is related to space and takes note of spatial characteristics and attributes. It studies the patterns of distribution, location and concentration of phenomena over space and interprets them providing explanations for these patterns. It takes note of the associations and inter relationships between the phenomena over space and interprets them providing explanations for these patterns. It also takes note of the associations and inter-relationships between the phenomena resulting from the dynamic interaction between human beings and their physical environment.

GEOGRAPHY

AS AN

INTEGRATING DISCIPLINE

Geography is a discipline of synthesis. It attempts spatial synthesis, and history attempts temporal synthesis. Its approach is holistic in nature. It recognises the fact that the world is a system of interdependencies. The

present world is being perceived as a global village. The distances have been reduced by better means of transportation increasing accessibility. The audio-visual media and information technology have enriched the data base. Technology has provided better chances of monitoring natural phenomena as well as the economic and social parameters. Geography as an integrating discipline has interface with numerous natural and social sciences. All the sciences, whether natural or social, have one basic objective, of understanding the reality. Geography attempts to comprehend the associations of phenomena as related in sections of reality. Figure 1.1 shows the relationship of geography with other sciences. Every discipline, concerned with scientific knowledge is linked with geography as many of their elements vary over space. Geography helps in understanding the reality in totality in its spatial perspective. Geography, thus, not only takes note of the differences in the phenomena from place to place but integrates them holistically which may be different at other places. A geographer is required to have a broad understanding of all the related fields, to be able to logically integrate them. This integration can be understood with some examples. Geography influences historical events. Spatial distance itself has been a very potent factor to alter the course of history of the world. Spatial depth provided defence to many countries, particularly in the last century. In traditional warfare, countries with large size in area, gain time at the cost of space. The defence provided by oceanic expanse around the countries of the new world has protected them from wars being imposed on their soil. If we look at the historical events world over, each one of them can be interpreted geographically. In India, Himalayas have acted as great barriers and provided protection but the passes provided routes to the migrants and invaders from Central Asia. The sea coast has encouraged contact with people from East and Southeast Asia, Europe and Africa. Navigation technology helped European countries to colonise a number of countries of Asia and Africa, including India as they got accessibility

5

GEOGRAPHY AS A DISCIPLINE

through oceans. The geographical factors have modified the course of history in different parts of the world. Every geographical phenomenon undergoes change through time and can be explained temporally. The changes in landforms, climate, vegetation, economic activities occupations and cultural developments have followed a definite historical course. Many geographical features result from the decision making process by different institutions at a particular point of time. It is possible to convert time in terms of space and space in terms of time. For example, it can be said that place A is 1,500 km from place B or alternately, it can also be said that place A is two hours away (if one travels by plane) or seventeen hours away (if one travels by a fast moving train). It is for this reason, time is an integral part of geographical studies as the fourth dimension. Please mention other three dimensions? Figure1.1 amply depicts the linkages of geography with different natural and social sciences. This linkage can be put under two segments. Physical Geography and Natural Sciences All the branches of physical geography, as shown in Figure 1.1, have interface with natural sciences. The traditional physical geography is linked with geology, meteorology, hydrology and pedology, and thus, geomorphology, climatology, oceanography and soil geography respectively have very close link with the natural sciences as these derive their data from these sciences. Bio-Geography is closely related to botany, zoology as well as ecology as human beings are located in different locational niche. A geographer should have some proficiency in mathematics and art, particularly in drawing maps. Geography is very much linked with the study of astronomical locations and deals with latitudes and longitudes. The shape of the earth is Geoid but the basic tool of a geographer is a map which is two dimensional representation of the earth. The problem of converting geoids into two dimensions can be tackled by projections constructed graphically or mathematically. The cartographic and quantitative techniques require sufficient proficiency in mathematics, statistics and

econometrics. Maps are prepared through artistic imagination. Making sketches, mental maps and cartographic work require proficiency in arts. Geography and Social Sciences Each social science sketched in Figure 1.1 has interface with one branch of geography. The relationships between geography and history have already been outlined in detail. Every discipline has a philosophy which is the raison d’etre for that discipline. Philosophy provides roots to a discipline and in the process of its evolution, it also experiences distinct historical processes. Thus, the history of geographical thought as mother branch of geography is included universally in its curricula. All the social science disciplines, viz. sociology, political science, economics and demography study different aspects of social reality. The branches of geography, viz. social, political, economic and population and settlements are closely linked with these disciplines as each one of them has spatial attributes. The core concern of political science is territory, people and sovereignty while political geography is also interested in the study of the state as a spatial unit as well as people and their political behaviour. Economics deals with basic attributes of the economy such as production, distribution, exchange and consumption. Each of these attributes also has spatial aspects and here comes the role of economic geography to study the spatial aspects of production, distribution, exchange and consumption. Likewise, population geography is closely linked with the discipline of demography. The above discussion shows that geography has strong interface with natural and social sciences. It follows its own methodology of study which makes it distinct from others. It has osmotic relationship with other disciplines. While all the disciplines have their own individual scope, this individuality does not obstruct the flow of information as in case of all cells in the body that have individual identity separated by membranes but the flow of blood is not obstructed. Geographers use data obtained from sister disciplines and

Figure 1.1 : Geography and its relation with other subjects

6 FUNDAMENTALS OF PHYSICAL GEOGRAPHY

7

GEOGRAPHY AS A DISCIPLINE

attempt synthesis over space. Maps are very effective tools of geographers in which the tabular data is converted into visual form to bring out the spatial pattern.

BRANCHES

OF

GEOGRAPHY

Please study Figure 1.1 for recapitulation. It has very clearly brought out that geography is an interdisciplinary subject of study. The study of every subject is done according to some approach. The major approaches to study geography have been (i) Systematic and (ii) Regional. The systematic geography approach is the same as that of general geography. This approach was introduced by Alexander Von Humboldt, a German geographer (1769-1859) while regional geography approach was developed by another German geographer and a contemporary of Humboldt, Karl Ritter (1779-1859). In systematic approach (Figure 1.2), a phenomenon is studied world over as a whole, and then the identification of typologies or spatial patterns is done. For example, if one is interested in studying natural vegetation, the study will be done at the world level as a first step. The typologies such as equatorial rain forests or softwood conical forests or monsoon forests, etc. will be identified, discussed and delimited. In the regional approach, the world is divided into regions at different hierarchical levels and then all the geographical phenomena in a particular region are studied. These regions may be natural, political or designated region. The phenomena in a region are studied in a holistic manner searching for unity in diversity. Dualism is one of the main characteristics of geography which got introduced from the very beginning. This dualism depended on the aspect emphasised in the study. Earlier scholars laid emphasis on physical geography. But human beings are an integral part of the earth’s surface. They are part and parcel of nature. They also have contributed through their cultural development. Thus developed human geography with emphasis on human activities.

BRANCHES OF GEOGRAPHY (BASED SYSTEMATIC APPROACH)

ON

1. Physical Geography (i) Geomorphology is devoted to the study of landforms, their evolution and related processes. (ii) Climatology encompasses the study of structure of atmosphere and elements of weather and climates and climatic types and regions. (iii) Hydrology studies the realm of water over the surface of the earth including oceans, lakes, rivers and other water bodies and its effect on different life forms including human life and their activities. (iv) Soil Geography is devoted to study the processes of soil formation, soil types, their fertility status, distribution and use. 2. Human Geography (i) Social/Cultural Geography encompasses the study of society and its spatial dynamics as well as the cultural elements contributed by the society. (ii) Population and Settlement Geography (Rural and Urban). It studies population growth, distribution, density, sex ratio, migration and occupational structure etc. Settlement geography studies the characteristics of rural and urban settlements. (iii) Economic Geography studies economic activities of the people including agriculture, industry, tourism, trade, and transport, infrastructure and services, etc. (iv) Historical Geography studies the historical processes through which the space gets organised. Every region has undergone some historical experiences before attaining the present day status. The geographical features also experience temporal changes and these form the concerns of historical geography.

8

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Figure 1.2 : Branches of geography based on systematic approach

(v) Political Geography looks at the space from the angle of political events and studies boundaries, space relations between neighbouring political units, delimitation of constituencies, election scenario and develops theoretical framework to understand the political behaviour of the population.

3. Biogeography The interface between physical geography and human geography has lead to the development of Biogeography which includes: (i) Plant Geography which studies the spatial pattern of natural vegetation in their habitats.

9

GEOGRAPHY AS A DISCIPLINE

(ii) Zoo Geography which studies the spatial patterns and geographic characteristics of animals and their habitats. (iii) Ecology /Ecosystem deals with the scientific study of the habitats characteristic of species. (iv) Environmental Geography concerns world over leading to the realisation of environmental problems such as land gradation, pollution and concerns for conservation has resulted in the introduction of this new branch in geography.

BRANCHES OF GEOGRAPHY BASED ON REGIONAL APPROACH (FIGURE1.3) 1. Regional Studies/Area Studies Comprising Macro, Meso and Micro Regional Studies 2. Regional Planning Comprising Country/Rural and Town/ Urban Planning 3. Regional Development 4. Regional Analysis There are two aspects which are common to every discipline, these are: (i) Philosophy (a) Geographical Thought (b) Land and Human Interaction/ Human Ecology (ii) Methods and Techniques (a) Cartography including Computer Cartography (b) Quantitative Techniques/Statistical Techniques

(c) Field Survey Methods (d) Geo-informatics comprising techniques such as Remote Sensing, GIS, GPS, etc. The above classification gives a comprehensive format of the branches of geography. Generally geography curricula is taught and learnt in this format but this format is not static. Any discipline is bound to grow with new ideas, problems, methods and techniques. For example, what was once manual cartography has now been transformed into computer cartography. Technology has enabled scholars to handle large quantum of data. The internet provides extensive information. Thus, the capacity to attempt analysis has increased tremendously. GIS has further opened vistas of knowledge. GPS has become a handy tool to find out exact locations. Technologies have enhanced the capacity of attempting synthesis with sound theoretical understanding. You will learn some preliminary aspects of these techniques in your book, Practical work in Geography – Part I (NCERT, 2006). You will continue to improve upon your skills and learn about their application.

PHYSICAL GEOGRAPHY

AND ITS

IMPORTANCE

This chapter appears in the book entitled Fundamentals of Physical Geography. The contents of the book clearly reflect its scope. It is therefore, appropriate to know the importance of this branch of geography.

Figure 1.3 : Branches of geography based on regional approach

10

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Physical geography includes the study of lithosphere (landforms, drainage, relief and physiography), atmosphere (its composition, structure, elements and controls of weather and climate; temperature, pressure, winds, precipitation, climatic types, etc.), hydrosphere (oceans, seas, lakes and associated features with water realm) and biosphere ( life forms including human being and macro-organism and their sustaining mechanism, viz. food chain, ecological parameters and ecological balance). Soils are formed through the process of pedogenesis and depend upon the parent rocks, climate, biological activity and time. Time provides maturity to soils and helps in the development of soil profiles. Each element is important for human beings. Landforms provide the base on which human activities are located. The plains are utilised for agriculture. Plateaus provide forests and minerals. Mountains provide pastures, forests, tourist spots and are sources of rivers providing water to lowlands. Climate influences our house types, clothing and food habits. The climate has a profound effect on vegetation, cropping pattern, livestock farming and some industries, etc. Human beings have developed technologies which modify climatic elements in a restricted space such as air conditioners and coolers. Temperature and precipitation ensure the density of forests and quality of grassland. In India, monsoonal rainfall sets the agriculture rhythm in motion. Precipitation recharges the ground water aquifers which later provides water for agriculture and domestic use. We study oceans which are the store house of resources. Besides fish and other

sea-food, oceans are rich in mineral resources. India has developed the technology for collecting manganese nodules from oceanic bed. Soils are renewable resources, which influence a number of economic activities such as agriculture. The fertility of the soil is both naturally determined and culturally induced. Soils also provide the basis for the biosphere accommodating plants, animals and micro organisms. What is Geography? Geography is concerned with the description and explanation of the areal differentiation of the earth’s surface. Richard Hartshorne Geography studies the differences of phenomena usually related in different parts of the earth’s surface. Hettner

The study of physical geography is emerging as a discipline of evaluating and managing natural resources. In order to achieve this objective, it is essential to understand the intricate relationship between physical environment and human beings. Physical environment provides resources, and human beings utilise these resources and ensure their economic and cultural development. Accelerated pace of resource utilisation with the help of modern technology has created ecological imbalance in the world. Hence, a better understanding of physical environment is absolutely essential for sustainable development.

EXERCISES 1.

Multiple choice questions. (i)

(ii)

Which one of the following scholars coined the term ‘Geography’? (a) Herodotus

(c) Galileo

(b) Erathosthenese

(d) Aristotle

Which one of the following features can be termed as ‘physical feature’? (a) Port

(c) Plain

(b) Road

(d) Water park

11

GEOGRAPHY AS A DISCIPLINE

(iii) Make correct pairs from the following two columns and mark the correct option.

(iv)

(v)

2.

3.

1. Meteorology

A. Population Geography

2. Demography

B. Soil Geography

3. Sociology

C. Climatology

4. Pedology

D. Social Geography

(a) 1B,2C,3A,4D

(c) 1D,2B,3C,4A

(b) 1A,2D,3B,4C

(d) 1C,2A,3D,4B

Which one of the following questions is related to cause-effect relationship? (a) Why

(c) What

(b) Where

(d) When

Which one of the following disciplines attempts temporal synthesis? (a) Sociology

(c) Anthropology

(b) Geography

(d) History

Answer the following questions in about 30 words. (i)

What important cultural features do you observe while going to school? Are they similar or dissimilar? Should they be included in the study of geography or not? If yes, why?

(ii)

You have seen a tennis ball, a cricket ball, an orange and a pumpkin. Which one amongst these resembles the shape of the earth? Why have you chosen this particular item to describe the shape of the earth?

(iii)

Do you celebrate Van Mahotsava in your school? Why do we plant so many trees? How do the trees maintain ecological balance?

(iv)

You have seen elephants, deer, earthworms, trees and grasses. Where do they live or grow? What is the name given to this sphere? Can you describe some of the important features of this sphere?

(v)

How much time do you take to reach your school from your house? Had the school been located across the road from your house, how much time would you have taken to reach school? What is the effect of the distance between your residence and the school on the time taken in commuting? Can you convert time into space and vice versa?

Answer the following questions in about 150 words. (i)

You observe every day in your surroundings that there is variation in natural as well as cultural phenomena. All the trees are not of the same variety. All the birds and animals you see, are different. All these different elements are found on the earth. Can you now argue that geography is the study of “areal differentiation”?

(ii)

You have already studied geography, history, civics and economics as parts of social studies. Attempt an integration of these disciplines highlighting their interface.

12

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Project Work Select forest as a natural resource. (i) (ii) (iii)

Prepare a map of India showing the distribution of different types of forests. Write about the economic importance of forests for the country. Prepare a historical account of conservation of forests in India with focus on Chipko movements in Rajasthan and Uttaranchal.

UNIT II THE EARTH This unit deals with •

Origin and evolution of the earth; Interior of the earth; Wegener’s continental drift theory and plate tectonics; earthquakes and volcanoes

CHAPTER

THE ORIGIN

AND OF

D

EVOLUTION THE EARTH

Starry nights have always attracted us since the childhood. You may also have thought of these stars and had numerous questions in your mind. Questions such as how many stars are there in the sky? How did they come into existence? Can one reach the end of the sky? May be many more such questions are still there in your mind. In this chapter, you will learn how these “twinkling little stars” were formed. With that you will eventually also read the story of origin and evolution of the earth.

argument. At a later date, the arguments considered of a companion to the sun to have been coexisting. These arguments are called binary theories. In 1950, Otto Schmidt in Russia and Carl Weizascar in Germany somewhat revised the ‘nebular hypothesis’, though differing in details. They considered that the sun was surrounded by solar nebula containing mostly the hydrogen and helium along with what may be termed as dust. The friction and collision of particles led to formation of a disk-shaped cloud and the planets were formed through the process of accretion.

ORIGIN

Modern Theories

o you remember the nursery rhyme “…Twinkle, Twinkle little star…”?

OF THE

EARTH

Early Theories A large number of hypotheses were put forth by different philosophers and scientists regarding the origin of the earth. One of the earlier and popular arguments was by German philosopher Immanuel Kant. Mathematician Laplace revised it in 1796. It is known as Nebular Hypothesis. The hypothesis considered that the planets were formed out of a cloud of material associated with a youthful sun, which was slowly rotating. Later in 1900, Chamberlain and Moulton considered that a wandering star approached the sun. As a result, a cigar-shaped extension of material was separated from the solar surface. As the passing star moved away, the material separated from the solar surface continued to revolve around the sun and it slowly condensed into planets. Sir James Jeans and later Sir Harold Jeffrey supported this

However, scientists in later period took up the problems of origin of universe rather than that of just the earth or the planets. The most popular argument regarding the origin of the universe is the Big Bang Theory. It is also called expanding universe hypothesis. Edwin Hubble, in 1920, provided evidence that the universe is expanding. As time passes, galaxies move further and further apart. You can experiment and find what does the expanding universe mean. Take a balloon and mark some points on it to represent the galaxies. Now, if you start inflating the balloon, the points marked on the balloon will appear to be moving away from each other as the balloon expands. Similarly, the distance between the galaxies is also found to be increasing and thereby, the universe is considered to be expanding. However, you will find that besides the increase in the distances between the points on the

15

THE ORIGIN AND EVOLUTION OF THE EARTH

balloon, the points themselves are expanding. This is not in accordance with the fact. Scientists believe that though the space between the galaxies is increasing, observations do not support the expansion of galaxies. So, the balloon example is only partially correct.

The expansion of universe means increase in space between the galaxies. An alternative to this was Hoyle’s concept of steady state. It considered the universe to be roughly the same at any point of time. However, with greater evidence becoming available about the expanding universe, scientific community at present favours argument of expanding universe. The Star Formation

Figure 2.1 : The Big Bang

The Big Bang Theory considers the following stages in the development of the universe. (i) In the beginning, all matter forming the universe existed in one place in the form of a “tiny ball” (singular atom) with an unimaginably small volume, infinite temperature and infinite density. (ii) At the Big Bang the “tiny ball” exploded violently. This led to a huge expansion. It is now generally accepted that the event of big bang took place 13.7 billion years before the present. The expansion continues even to the present day. As it grew, some energy was converted into matter. There was particularly rapid expansion within fractions of a second after the bang. Thereafter, the expansion has slowed down. Within first three minutes from the Big Bang event, the first atom began to form. (iii) Within 300,000 years from the Big Bang, temperature dropped to 4,500 K and gave rise to atomic matter. The universe became transparent.

The distribution of matter and energy was not even in the early universe. These initial density differences gave rise to differences in gravitational forces and it caused the matter to get drawn together. These formed the bases for development of galaxies. A galaxy contains a large number of stars. Galaxies spread over vast distances that are measured in thousands of light-years. The diameters of individual galaxies range from 80,000-150,000 light years. A galaxy starts to form by accumulation of hydrogen gas in the form of a very large cloud called nebula. Eventually, growing nebula develops localised clumps of gas. These clumps continue to grow into even denser gaseous bodies, giving rise to formation of stars. The formation of stars is believed to have taken place some 5-6 billion years ago. A light year is a measure of distance and not of time. Light travels at a speed of 300,000 km/second. Considering this, the distances the light will travel in one year is taken to be one light year. This equals to 9.461×10 12 km. The mean distance between the sun and the earth is 149,598,000 km. In terms of light years, it is 8.311 minutes of a year.

Formation of Planets The following are considered to be the stages in the development of planets : (i) The stars are localised lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud and a huge rotating disc of gas and dust develops around the gas core.

16

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

(ii)

(iii)

In the next stage, the gas cloud starts getting condensed and the matter around the core develops into smallrounded objects. These small-rounded objects by the process of cohesion develop into what is called planetesimals. Larger bodies start forming by collision, and gravitational attraction causes the material to stick together. Planetesimals are a large number of smaller bodies. In the final stage, these large number of small planetesimals accrete to form a fewer large bodies in the form of planets.

OUR SOLAR SYSTEM Our Solar system consists of nine planets. The tenth planet 2003 UB313 has also been recently sighted. The nebula from which our Solar system is supposed to have been formed, started its collapse and core formation some time 5-5.6 billion years ago and the planets were formed about 4.6 billion years ago. Our solar system consists of the sun (the star), 9 planets, 63 moons, millions of smaller bodies like asteroids and comets and huge quantity of dust-grains and gases. Out of the nine planets, mercury, venus, earth and mars are called as the inner planets as they lie between the sun and the belt of asteroids the other five planets are called the outer planets. Alternatively, the first four are called Terrestrial, meaning earth-like as they are made up of rock and metals, and have relatively high densities. The rest five are called Jovian or Gas Giant planets. Jovian means jupiter-like. Most

of them are much larger than the terrestrial planets and have thick atmosphere, mostly of helium and hydrogen. All the planets were formed in the same period sometime about 4.6 billion years ago. Some data regarding our solar system are given in the box below. Why are the inner planets rocky while others are mostly in gaseous form?

The difference between terrestrial and jovian planets can be attributed to the following conditions: (i) The terrestrial planets were formed in the close vicinity of the parent star where it was too warm for gases to condense to solid particles. Jovian planets were formed at quite a distant location. (ii) The solar wind was most intense nearer the sun; so, it blew off lots of gas and dust from the terrestrial planets. The solar winds were not all that intense to cause similar removal of gases from the Jovian planets. (iii) The terrestrial planets are smaller and their lower gravity could not hold the escaping gases. The Moon The moon is the only natural satellite of the earth. Like the origin of the earth, there have been attempts to explain how the moon was formed. In 1838, Sir George Darwin suggested that initially, the earth and the moon formed a single rapidly rotating body. The whole mass

The Solar System Mercury

Venus

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Distance*

0.387

0.723

1.000

1.524

5.203

9.539

19.182

30.058

Density@

5.44

5.245

5.517

3.945

1.33

0.70

1.17

1.66

0.5-0.9

Radius#

0.383

0.949

1.000

0.533

11.19

9.460

4.11

3.88

-0.3

Satellites

0

0

1

2

16

about 18 about 17

8

Pluto 39.785

1

* Distance from the sun in astronomical unit i.e. average mean distance of the earth is 149,598,000 km = 1 @ Density in gm/cm3 # Radius: Equatorial radius 6378.137 km = 1

THE ORIGIN AND EVOLUTION OF THE EARTH

became a dumb-bell-shaped body and eventually it broke. It was also suggested that the material forming the moon was separated from what we have at present the depression occupied by the Pacific Ocean. However, the present scientists do not accept either of the explanations. It is now generally believed that the formation of moon, as a satellite of the earth, is an outcome of ‘giant impact’ or what is described as “the big splat”. A body of the size of one to three times that of mars collided into the earth sometime shortly after the earth was formed. It blasted a large part of the earth into space. This portion of blasted material then continued to orbit the earth and eventually formed into the present moon about 4.44 billion years ago.

EVOLUTION

OF THE

EARTH

Do you know that the planet earth initially was a barren, rocky and hot object with a thin atmosphere of hydrogen and helium. This is far from the present day picture of the earth. Hence, there must have been some events– processes, which may have caused this change from rocky, barren and hot earth to a beautiful planet with ample amount of water and conducive atmosphere favouring the existence of life. In the following section, you will find out how the period, between the 4,600 million years and the present, led to the evolution of life on the surface of the planet. The earth has a layered structure. From the outermost end of the atmosphere to the centre of the earth, the material that exists is not uniform. The atmospheric matter has the least density. From the surface to deeper depths, the earth’s interior has different zones and each of these contains materials with different characteristics. How was the layered structure of the earth developed?

Development of Lithosphere The earth was mostly in a volatile state during its primordial stage. Due to gradual increase in density the temperature inside has increased. As a result the material inside

17

started getting separated depending on their densities. This allowed heavier materials (like iron) to sink towards the centre of the earth and the lighter ones to move towards the surface. With passage of time it cooled further and solidified and condensed into a smaller size. This later led to the development of the outer surface in the form of a crust. During the formation of the moon, due to the giant impact, the earth was further heated up. It is through the process of differentiation that the earth forming material got separated into different layers. Starting from the surface to the central parts, we have layers like the crust, mantle, outer core and inner core. From the crust to the core, the density of the material increases. We shall discuss in detail the properties of each of this layer in the next chapter. Evolution of Atmosphere and Hydrosphere The present composition of earth’s atmosphere is chiefly contributed by nitrogen and oxygen. You will be dealing with the composition and structure of the earth’s atmosphere in Chapter 8. There are three stages in the evolution of the present atmosphere. The first stage is marked by the loss of primordial atmosphere. In the second stage, the hot interior of the earth contributed to the evolution of the atmosphere. Finally, the composition of the atmosphere was modified by the living world through the process of photosynthesis. The early atmosphere, with hydrogen and helium, is supposed to have been stripped off as a result of the solar winds. This happened not only in case of the earth, but also in all the terrestrial planets, which were supposed to have lost their primordial atmosphere through the impact of solar winds. During the cooling of the earth, gases and water vapour were released from the interior solid earth. This started the evolution of the present atmosphere. The early atmosphere largely contained water vapour, nitrogen, carbon dioxide, methane, ammonia and very little of free oxygen. The process through which the gases were outpoured from the interior is called degassing. Continuous volcanic eruptions contributed water vapour and gases

18

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Geological Time Scale Eons

Era

Period Quaternary

Cainozoic (From 65 million years to the present times)

Mesozoic 65 - 245 Million Mammals

Palaeozoic 245 - 570 Million

Tertiary

Epoch

Age/ Years Before Present

Life/ Major Events

Holocene Pleistocene Pliocene Miocene

0 - 10,000 10,000 - 2 million 2 - 5 million 5 - 24 million

Oligocene Eocene Palaeocene

24 - 37 Ma 37 - 58 Million 57 - 65 Million

Modern Man Homo Sapiens Early Human Ancestor Ape: Flowering Plants and Trees Anthropoid Ape Rabbits and Hare Small Mammals : Rats – Mice

Cretaceous Jurassic Triassic

65 - 144 Million 144 - 208 Million 208 - 245 Million

Extinction of Dinosaurs Age of Dinosaurs Frogs and turtles

Permian

245 - 286 Million

Carboniferous

286 - 360 Million

Devonian Silurian

360 - 408 Million 408 - 438 Million

Ordovician Cambrian

438 - 505 Million 505 - 570 Million

Reptile dominate-replace amphibians First Reptiles: Vertebrates: Coal beds Amphibians First trace of life on land: Plants First Fish No terrestrial Life : Marine Invertebrate Soft-bodied arthropods Blue green Algae: Unicellular bacteria Oceans and Continents form – Ocean and Atmosphere are rich in Carbon dioxide

Proterozoic Archean Hadean

Origin of Stars Supernova

570 - 2,500 Million 2,500 - 3,800 Million PreCambrian 570 Million - 4,800 Million

5,000 13,700 Million

Big Bang

to the atmosphere. As the earth cooled, the water vapour released started getting condensed. The carbon dioxide in the atmosphere got dissolved in rainwater and the temperature further decreased causing more condensation and more rains. The rainwater falling onto the surface got collected in the depressions to give rise to oceans. The earth’s oceans were formed within 500 million years from the formation of the earth. This tells us

3,800 - 4,800 Million

5,000 Million

Origin of the sun

12,000 Million

Origin of the universe

13,700 Million

that the oceans are as old as 4,000 million years. Sometime around 3,800 million years ago, life began to evolve. However, around 2,500-3,000 million years before the present, the process of photosynthesis got evolved. Life was confined to the oceans for a long time. Oceans began to have the contribution of oxygen through the process of photosynthesis. Eventually, oceans were saturated with oxygen, and 2,000 million years ago, oxygen began to flood the atmosphere.

19

THE ORIGIN AND EVOLUTION OF THE EARTH

Origin of Life

living substance. The record of life that existed on this planet in different periods is found in rocks in the form of fossils. The microscopic structures closely related to the present form of blue algae have been found in geological formations that are much older than these were some 3,000 million years ago. It can be assumed that life began to evolve sometime 3,800 million years ago. The summary of evolution of life from unicellular bacteria to the modern man is given in the Geological Time Scale on page 18.

The last phase in the evolution of the earth relates to the origin and evolution of life. It is undoubtedly clear that the initial or even the atmosphere of the earth was not conducive for the development of life. Modern scientists refer to the origin of life as a kind of chemical reaction, which first generated complex organic molecules and assembled them. This assemblage was such that they could duplicate themselves converting inanimate matter into

EXERCISES 1.

Multiple choice questions. (i)

Which one of the following figures represents the age of the earth? (a) 4.6 million years (b) 13.7 billion years

(ii)

(iii)

(iv)

(v)

2.

(c) 4.6 billion years (d) 13.7 trillion years

Which one of the following has the longest duration? (a) Eons

(c) Era

(b) Period

(d) Epoch

Which one of the following is not related to the formation or modification of the present atmosphere? (a) Solar winds

(c) Degassing

(b) Differentiation

(d) Photosynthesis

Which one of the following represents the inner planets? (a)

Planets between the sun and the earth

(b)

Planets between the sun and the belt of asteroids

(c)

Planets in gaseous state

(d)

Planets without satellite(s)

Life on the earth appeared around how many years before the present? (a) 13.7 billion

(c) 4.6 billion

(b) 3.8 million

(d) 3.8 billion

Answer the following questions in about 30 words. (i) (ii)

Why are the terrestrial planets rocky? What is the basic difference in the arguments related to the origin of the earth given by : (a)

Kant and Laplace

(b)

Chamberlain and Moulton

20

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

(iii)

What is meant by the process of differentiation?

(iv)

What was the nature of the earth surface initially?

(v) 3.

What were the gases which initially formed the earth’s atmosphere?

Answer the following questions in about 150 words. (i) (ii)

Write an explanatory note on the ‘Big Bang Theory’. List the stages in the evolution of the earth and explain each stage in brief.

Project Work Collect information about the project “Stardust” (website: www.sci.edu/public.html and www.nasm.edu) along the following lines. (i)

Which is the agency that has launched this project?

(ii)

Why are scientists interested in collecting Stardust?

(iii)

Where from has the Stardust been collected?

CHAPTER

INTERIOR

W

OF THE

EARTH

hat do you imagine about the nature of the earth? Do you imagine it to be a solid ball like cricket ball or a hollow ball with a thick cover of rocks i.e. lithosphere? Have you ever seen photographs or images of a volcanic eruption on the television screen? Can you recollect the emergence of hot molten lava, dust, smoke, fire and magma flowing out of the volcanic crater? The interior of the earth can be understood only by indirect evidences as neither any one has nor any one can reach the interior of the earth. The configuration of the surface of the earth is largely a product of the processes operating in the interior of the earth. Exogenic as well as endogenic processes are constantly shaping the landscape. A proper understanding of the physiographic character of a region remains incomplete if the effects of endogenic processes are ignored. Human life is largely influenced by the physiography of the region. Therefore, it is necessary that one gets acquainted with the forces that influence landscape development. To understand why the earth shakes or how a tsunami wave is generated, it is necessary that we know certain details of the interior of the earth. In the previous chapter, you have noted that the earth-forming materials have been distributed in the form of layers from the crust to the core. It is interesting to know how scientists have gathered information about these layers and what are the characteristics of each of these layers. This is exactly what this chapter deals with.

SOURCES

OF

INFORMATION ABOUT THE INTERIOR

The earth’s radius is 6,370 km. No one can reach the centre of the earth and make observations or collect samples of the material. Under such conditions, you may wonder how scientists tell us about the earth’s interior and the type of materials that exist at such depths. Most of our knowledge about the interior of the earth is largely based on estimates and inferences. Yet, a part of the information is obtained through direct observations and analysis of materials. Direct Sources The most easily available solid earth material is surface rock or the rocks we get from mining areas. Gold mines in South Africa are as deep as 3 - 4 km. Going beyond this depth is not possible as it is very hot at this depth. Besides mining, scientists have taken up a number of projects to penetrate deeper depths to explore the conditions in the crustal portions. Scientists world over are working on two major projects such as “Deep Ocean Drilling Project” and “Integrated Ocean Drilling Project”. The deepest drill at Kola, in Arctic Ocean, has so far reached a depth of 12 km. This and many deep drilling projects have provided large volume of information through the analysis of materials collected at different depths. Volcanic eruption forms another source of obtaining direct information. As and when the molten material (magma) is thrown onto the surface of the earth, during volcanic eruption it becomes available for laboratory analysis. However, it is difficult to ascertain the depth of the source of such magma.

22

Indirect Sources Analysis of properties of matter indirectly provides information about the interior. We know through the mining activity that temperature and pressure increase with the increasing distance from the surface towards the interior in deeper depths. Moreover, it is also known that the density of the material also increases with depth. It is possible to find the rate of change of these characteristics. Knowing the total thickness of the earth, scientists have estimated the values of temperature, pressure and the density of materials at different depths. The details of these characteristics with reference to each layer of the interior are discussed later in this chapter. Another source of information are the meteors that at times reach the earth. However, it may be noted that the material that becomes available for analysis from meteors, is not from the interior of the earth. The material and the structure observed in the meteors are similar to that of the earth. They are solid bodies developed out of materials same as, or similar to, our planet. Hence, this becomes yet another source of information about the interior of the earth. The other indirect sources include gravitation, magnetic field, and seismic activity. The gravitation force (g) is not the same at different latitudes on the surface. It is greater near the poles and less at the equator. This is because of the distance from the centre at the equator being greater than that at the poles. The gravity values also differ according to the mass of material. The uneven distribution of mass of material within the earth influences this value. The reading of the gravity at different places is influenced by many other factors. These readings differ from the expected values. Such a difference is called gravity anomaly. Gravity anomalies give us information about the distribution of mass of the material in the crust of the earth. Magnetic surveys also provide information about the distribution of magnetic materials in the crustal portion, and thus, provide information about the distribution of materials in this part. Seismic activity is one of the most important sources of

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

information about the interior of the earth. Hence, we shall discuss it in some detail. Earthquake The study of seismic waves provides a complete picture of the layered interior. An earthquake in simple words is shaking of the earth. It is a natural event. It is caused due to release of energy, which generates waves that travel in all directions. Why does the earth shake? The release of energy occurs along a fault. A fault is a sharp break in the crustal rocks. Rocks along a fault tend to move in opposite directions. As the overlying rock strata press them, the friction locks them together. However, their tendency to move apart at some point of time overcomes the friction. As a result, the blocks get deformed and eventually, they slide past one another abruptly. This causes a release of energy, and the energy waves travel in all directions. The point where the energy is released is called the focus of an earthquake, alternatively, it is called the hypocentre. The energy waves travelling in different directions reach the surface. The point on the surface, nearest to the focus, is called epicentre. It is the first one to experience the waves. It is a point directly above the focus. Earthquake Waves All natural earthquakes take place in the lithosphere. You will learn about different layers of the earth later in this chapter. It is sufficient to note here that the lithosphere refers to the portion of depth up to 200 km from the surface of the earth. An instrument called ‘seismograph’ records the waves reaching the surface. A curve of earthquake waves recorded on the seismograph is given in Figure 3.1. Note that the curve shows three distinct sections each representing different types of wave patterns. Earthquake waves are basically of two types — body waves and surface waves. Body waves are generated due to the release of energy at the focus and move in all directions travelling through the body of the earth. Hence, the name

23

INTERIOR OF THE EARTH

body waves. The body waves interact with the surface rocks and generate new set of waves called surface waves. These waves move along the surface. The velocity of waves changes as they travel through materials with different densities. The denser the material, the higher is the velocity. Their direction also changes as they reflect or refract when coming across materials with different densities.

propagation. As a result, it creates density differences in the material leading to stretching and squeezing of the material. Other three waves vibrate perpendicular to the direction of propagation. The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane. Hence, they create troughs and crests in the material through which they pass. Surface waves are considered to be the most damaging waves. Emergence of Shadow Zone

Figure 3.1 : Earthquake Waves

There are two types of body waves. They are called P and S-waves. P-waves move faster and are the first to arrive at the surface. These are also called ‘primary waves’. The P-waves are similar to sound waves. They travel through gaseous, liquid and solid materials. S-waves arrive at the surface with some time lag. These are called secondary waves. An important fact about S-waves is that they can travel only through solid materials. This characteristic of the S-waves is quite important. It has helped scientists to understand the structure of the interior of the earth. Reflection causes waves to rebound whereas refraction makes waves move in different directions. The variations in the direction of waves are inferred with the help of their record on seismograph. The surface waves are the last to report on seismograph. These waves are more destructive. They cause displacement of rocks, and hence, the collapse of structures occurs.

Earthquake waves get recorded in seismographs located at far off locations. However, there exist some specific areas where the waves are not reported. Such a zone is called the ‘shadow zone’. The study of different events reveals that for each earthquake, there exists an altogether different shadow zone. Figure 3.2 (a) and (b) show the shadow zones of P and S-waves. It was observed that seismographs located at any distance within 105° from the epicentre, recorded the arrival of both P and S-waves. However, the seismographs located beyond 145° from epicentre, record the arrival of P-waves, but not that of S-waves. Thus, a zone between 105° and 145° from epicentre was identified as the shadow zone for both the types of waves. The entire zone beyond 105° does not receive S-waves. The shadow zone of S-wave is much larger than that of the P-waves. The shadow zone of P-waves appears as a band around the earth between 105° and 145° away from the epicentre. The shadow zone of S-waves is not only larger in extent but it is also a little over 40 per cent of the earth surface. You can draw the shadow zone for any earthquake provided you know the location of the epicentre. (See the activity box on page 28 to know how to locate the epicentre of a quake event). Types of Earthquakes

Propagation of Earthquake Waves Different types of earthquake waves travel in different manners. As they move or propagate, they cause vibration in the body of the rocks through which they pass. P-waves vibrate parallel to the direction of the wave. This exerts pressure on the material in the direction of the

(i) The most common ones are the tectonic earthquakes. These are generated due to sliding of rocks along a fault plane. (ii) A special class of tectonic earthquake is sometimes recognised as volcanic earthquake. However, these are confined to areas of active volcanoes.

24

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

(v) The earthquakes that occur in the areas of large reservoirs are referred to as reservoir induced earthquakes. Measuring Earthquakes The earthquake events are scaled either according to the magnitude or intensity of the shock. The magnitude scale is known as the Richter scale. The magnitude relates to the energy released during the quake. The magnitude is expressed in absolute numbers, 0-10. The intensity scale is named after Mercalli, an Italian seismologist. The intensity scale takes into account the visible damage caused by the event. The range of intensity scale is from 1-12.

EFFECTS

Figure 3.2 (a) and (b) : Earthquake Shadow Zones

(iii) In the areas of intense mining activity, sometimes the roofs of underground mines collapse causing minor tremors. These are called collapse earthquakes. (iv) Ground shaking may also occur due to the explosion of chemical or nuclear devices. Such tremors are called explosion earthquakes.

OF

EARTHQUAKE

Earthquake is a natural hazard. The following are the immediate hazardous effects of earthquake: (i) Ground Shaking (ii) Differential ground settlement (iii) Land and mud slides (iv) Soil liquefaction (v) Ground lurching (vi) Avalanches (vii) Ground displacement (viii) Floods from dam and levee failures (ix) Fires (x) Structural collapse (xi) Falling objects (xii) Tsunami The first six listed above have some bearings upon landforms, while others may be considered the effects causing immediate concern to the life and properties of people in the region. The effect of tsunami would occur only if the epicentre of the tremor is below oceanic waters and the magnitude is sufficiently high. Tsunamis are waves generated by the tremors and not an earthquake in itself. Though the actual quake activity lasts for a few seconds, its effects are devastating provided the magnitude of the quake is more than 5 on the Richter scale.

25

INTERIOR OF THE EARTH

Frequency of Earthquake Occurrences

STRUCTURE

The earthquake is a natural hazard. If a tremor of high magnitude takes place, it can cause heavy damage to the life and property of people. However, not all the parts of the globe necessarily experience major shocks. We shall be discussing the distribution of earthquakes and volcanoes with some details in the next

The Crust

OF THE

EARTH

It is the outermost solid part of the earth. It is brittle in nature. The thickness of the crust varies under the oceanic and continental areas. Oceanic crust is thinner as compared to the continental crust. The mean thickness of oceanic crust is 5 km whereas that of the continental is around 30 km. The continental crust is thicker in the areas of major mountain systems. It is as much as 70 km thick in the Himalayan region. It is made up of heavier rocks having density of 3 g/cm3. This type of rock found in the oceanic crust is basalt. The mean density of material in oceanic crust is 2.7 g/cm3. The Mantle

A view of the damaged Aman Setu at the LOC in Uri, due to an earthquake

chapter. Note that the quakes of high magnitude, i.e. 8+ are quite rare; they occur once in 1-2 years whereas those of ‘tiny’ types occur almost every minute.

The portion of the interior beyond the crust is called the mantle. The mantle extends from Moho’s discontinuity to a depth of 2,900 km. The upper portion of the mantle is called asthenosphere. The word astheno means weak. It is considered to be extending upto 400 km. It is the main source of magma that finds

26

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

been released out in the recent past. The layer below the solid crust is mantle. It has higher density than that of the crust. The mantle contains a weaker zone called asthenosphere. It is from this that the molten rock materials find their way to the surface. The material in the upper mantle portion is called magma. Once it starts moving towards the crust or it reaches the surface, it is referred to as lava. The material that reaches the ground includes lava flows, pyroclastic debris, volcanic bombs, ash and dust and gases such as nitrogen compounds, sulphur compounds and minor amounts of chlorene, hydrogen and argon. Volcanoes

Figure 3.4 : The interior of the earth

its way to the surface during volcanic eruptions. It has a density higher than the crust’s (3.4 g/cm 3 ). The crust and the uppermost part of the mantle are called lithosphere. Its thickness ranges from 10-200 km. The lower mantle extends beyond the asthenosphere. It is in solid state.

Volcanoes are classified on the basis of nature of eruption and the form developed at the surface. Major types of volcanoes are as follows: Shield Volcanoes Barring the basalt flows, the shield volcanoes are the largest of all the volcanoes on the earth. The Hawaiian volcanoes are the most famous

The Core As indicated earlier, the earthquake wave velocities helped in understanding the existence of the core of the earth. The coremantle boundary is located at the depth of 2,900 km. The outer core is in liquid state while the inner core is in solid state. The density of material at the mantle core boundary is around 5 g/cm3 and at the centre of the earth at 6,300 km, the density value is around 13g/cm3. The core is made up of very heavy material mostly constituted by nickel and iron. It is sometimes referred to as the nife layer.

VOLCANOES

AND

Shield Volcano

VOLCANIC LANDFORMS

You may have seen photographs or pictures of volcanoes on a number of occasions. A volcano is a place where gases, ashes and/or molten rock material – lava – escape to the ground. A volcano is called an active volcano if the materials mentioned are being released or have

Cinder Cone

27

INTERIOR OF THE EARTH

examples. These volcanoes are mostly made up of basalt, a type of lava that is very fluid when erupted. For this reason, these volcanoes are not steep. They become explosive if somehow water gets into the vent; otherwise, they are characterised by low-explosivity. The upcoming lava moves in the form of a fountain and throws out the cone at the top of the vent and develops into cinder cone.

more than 50 m. Individual flows may extend for hundreds of km. The Deccan Traps from India, presently covering most of the Maharashtra plateau, are a much larger flood basalt province. It is believed that initially the trap formations covered a much larger area than the present.

Composite Volcanoes

These volcanoes occur in the oceanic areas. There is a system of mid-ocean ridges more than 70,000 km long that stretches through all the ocean basins. The central portion of this ridge experiences frequent eruptions. We shall be discussing this in detail in the next chapter.

These volcanoes are characterised by eruptions of cooler and more viscous lavas than basalt. These volcanoes often result in explosive eruptions. Along with lava, large quantities of pyroclastic material and ashes find their way to the ground. This material accumulates in the vicinity of the vent openings leading to formation of layers, and this makes the mounts appear as composite volcanoes.

Composite Volcano

Mid-Ocean Ridge Volcanoes

VOLCANIC LANDFORMS Intrusive Forms The lava that is released during volcanic eruptions on cooling develops into igneous rocks. The cooling may take place either on reaching the surface or also while the lava is still in the crustal portion. Depending on the location of the cooling of the lava, igneous rocks are classified as volcanic rocks (cooling at the surface) and plutonic rocks (cooling in the crust). The lava that cools within the crustal portions assumes different forms. These forms are called intrusive forms. Some of the forms are shown in Figure 3.5.

Caldera These are the most explosive of the earth’s volcanoes. They are usually so explosive that when they erupt they tend to collapse on themselves rather than building any tall structure. The collapsed depressions are called calderas. Their explosiveness indicates that the magma chamber supplying the lava is not only huge but is also in close vicinity. Flood Basalt Provinces These volcanoes outpour highly fluid lava that flows for long distances. Some parts of the world are covered by thousands of sq. km of thick basalt lava flows. There can be a series of flows with some flows attaining thickness of

Figure 3.5 : Volcanic Landforms

28

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Batholiths A large body of magmatic material that cools in the deeper depth of the crust develops in the form of large domes. They appear on the surface only after the denudational processes remove the overlying materials. They cover large areas, and at times, assume depth that may be several km. These are granitic bodies. Batholiths are the cooled portion of magma chambers.

conduit from below. It resembles the surface volcanic domes of composite volcano, only these are located at deeper depths. It can be regarded as the localised source of lava that finds its way to the surface. The Karnataka plateau is spotted with domal hills of granite rocks. Most of these, now exfoliated, are examples of lacoliths or batholiths.

Lacoliths These are large dome-shaped intrusive bodies with a level base and connected by a pipe-like

As and when the lava moves upwards, a portion of the same may tend to move in a horizontal direction wherever it finds a weak

Lapolith, Phacolith and Sills

Activity : Locating an Epicentre For this you will need Data from 3 seismograph stations about the time of arrival of P-waves, S-waves. Procedure 1. Find the time of arrival of P and S-waves of the given quake for the three stations for which you have the data. 2. Compute the time lag between the arrival of P and S-waves for each station; it is called time lag. (Note that it is directly related to the distance of the seismograph from the focus.) A. Basic rule : For every second of time lag, the earthquake is roughly 8 km away from you. 3. Using the rule quoted above, convert the time lag into distance ( # seconds of time lag * 8) for each station. 4. On a map locate the seismograph stations. 5. Draw circles, taking the seismograph stations as the centre, with the radius equal to the distance you have calculated in the previous step. (Do not forget to convert distance as per the map scale.) 6. These circles will intersect each other in a point. This point is the location of the epicentre. In normal practice, the epicentres are located using computer models. They take into account the structure of the earth’s crust. The locations with accuracy within a few hundred metres can be achieved. The procedure outlined here is a much simplified version of what is normally done, although the principle is the same. In the following diagram, the epicentre is located using this procedure. It also contains a table giving necessary data. Why don’t you try for yourself ? Data Station

Arrival time of P-waves S-waves Hour Min. Sec. Hour Min. Sec.

S1

03

23

20

03

24

45

S2

03

22

17

03

23

57

S3

03

22

00

03

23

55

Scale of the map 1cm = 40km

29

INTERIOR OF THE EARTH

plane. It may get rested in different forms. In case it develops into a saucer shape, concave to the sky body, it is called lapolith. A wavy mass of intrusive rocks, at times, is found at the base of synclines or at the top of anticline in folded igneous country. Such wavy materials have a definite conduit to source beneath in the form of magma chambers (subsequently developed as batholiths). These are called the phacoliths. The near horizontal bodies of the intrusive igneous rocks are called sill or sheet, depending on the thickness of the material. The thinner ones are called sheets

while the thick horizontal deposits are called sills. Dykes When the lava makes its way through cracks and the fissures developed in the land, it solidifies almost perpendicular to the ground. It gets cooled in the same position to develop a wall-like structure. Such structures are called dykes. These are the most commonly found intrusive forms in the western Maharashtra area. These are considered the feeders for the eruptions that led to the development of the Deccan traps.

EXERCISES 1.

Multiple choice questions. (i) Which one of the following earthquake waves is more destructive? (a) P-waves

(c) Surface waves

(b) S-waves

(d) None of the above

(ii) Which one of the following is a direct source of information about the interior of the earth? (a) Earthquake waves

(c) Gravitational force

(b) Volcanoes

(d) Earth magnetism

(iii) Which type of volcanic eruptions have caused Deccan Trap formations? (a) Shield

(c) Composite

(b) Flood

(d) Caldera

(iv) Which one of the following describes the lithosphere:

2.

(a) upper and lower mantle

(c) crust and core

(b) crust and upper mantle

(d) mantle and core

Answer the following questions in about 30 words. (i) (ii)

What are body waves? Name the direct sources of information about the interior of the earth.

(iii)

Why do earthquake waves develop shadow zone?

(iv)

Briefly explain the indirect sources of information of the interior of the earth other than those of seismic activity.

3. Answer the following questions in about 150 words. (i)

What are the effects of propagation of earthquake waves on the rock mass through which they travel?

(ii)

What do you understand by intrusive forms? Briefly describe various intrusive forms.

CHAPTER

DISTRIBUTION AND

In the previous chapter, you have studied the interior of the earth. You are already familiar with the world map. You know that continents cover 29 per cent of the surface of the earth and the remainder is under oceanic waters. The positions of the continents and the ocean bodies, as we see them in the map, have not been the same in the past. Moreover, it is now a well-accepted fact that oceans and continents will not continue to enjoy their present positions in times to come. If this is so, the question arises what were their positions in the past? Why and how do they change their positions? Even if it is true that the continents and oceans have changed and are changing their positions, you may wonder as to how scientists know this. How have they determined their earlier positions? You will find the answers to some of these and related questions in this chapter.

CONTINENTAL DRIFT Observe the shape of the coastline of the Atlantic Ocean. You will be surprised by the symmetry of the coastlines on either side of the ocean. No wonder, many scientists thought of this similarity and considered the possibility of the two Americas, Europe and Africa, to be once joined together. From the known records of the history of science, it was Abraham Ortelius, a Dutch map maker, who first proposed such a possibility as early as 1596. Antonio Pellegrini drew a map showing the three continents together. However, it was Alfred Wegener—a German meteorologist who put forth a comprehensive argument in the form of “the continental drift

OF

OCEANS

CONTINENTS

theory” in 1912. This was regarding the distribution of the oceans and the continents. According to Wegener, all the continents formed a single continental mass, a mega ocean surrounded by the same. The super continent was named PANGAEA, which meant all earth. The mega-ocean was called PANTHALASSA, meaning all water. He argued that, around 200 million years ago, the super continent, Pangaea, began to split. Pangaea first broke into two large continental masses as Laurasia and Gondwanaland forming the northern and southern components respectively. Subsequently, Laurasia and Gondwanaland continued to break into various smaller continents that exist today. A variety of evidence was offered in support of the continental drift. Some of these are given below. Evidence in Support of the Continental Drift The Matching of Continents (Jig-Saw-Fit) The shorelines of Africa and South America facing each other have a remarkable and unmistakable match. It may be noted that a map produced using a computer programme to find the best fit of the Atlantic margin was presented by Bullard in 1964. It proved to be quite perfect. The match was tried at 1,000fathom line instead of the present shoreline. Rocks of Same Age Across the Oceans The radiometric dating methods developed in the recent period have facilitated correlating the rock formation from different continents across

31

DISTRIBUTION OF OCEANS AND CONTINENTS

the vast ocean. The belt of ancient rocks of 2,000 million years from Brazil coast matches with those from western Africa. The earliest marine deposits along the coastline of South America and Africa are of the Jurassic age. This suggests that the ocean did not exist prior to that time. Tillite It is the sedimentary rock formed out of deposits of glaciers. The Gondawana system of sediments from India is known to have its counter parts in six different landmasses of the Southern Hemisphere. At the base the system has thick tillite indicating extensive and prolonged glaciation. Counter parts of this succession are found in Africa, Falkland Island, Madagascar, Antarctica and Australia besides India. Overall resemblance of the Gondawana type sediments clearly demonstrates that these landmasses had remarkably similar histories. The glacial tillite provides unambiguous evidence of palaeoclimates and also of drifting of continents. Placer Deposits The occurrence of rich placer deposits of gold in the Ghana coast and the absolute absence of source rock in the region is an amazing fact. The gold bearing veins are in Brazil and it is obvious that the gold deposits of the Ghana are derived from the Brazil plateau when the two continents lay side by side. Distribution of Fossils When identical species of plants and animals adapted to living on land or in fresh water are found on either side of the marine barriers, a problem arises regarding accounting for such distribution. The observations that Lemurs occur in India, Madagascar and Africa led some to consider a contiguous landmass “Lemuria” linking these three landmasses. Mesosaurus was a small reptile adapted to shallow brackish water. The skeletons of these are found only in two localities : the Southern Cape province of South Africa and Iraver formations of Brazil. The two localities presently are 4,800 km apart with an ocean in between them.

Force for Drifting Wegener suggested that the movement responsible for the drifting of the continents was caused by pole-fleeing force and tidal force. The polar-fleeing force relates to the rotation of the earth. You are aware of the fact that the earth is not a perfect sphere; it has a bulge at the equator. This bulge is due to the rotation of the earth. The second force that was suggested by Wegener—the tidal force—is due to the attraction of the moon and the sun that develops tides in oceanic waters. Wegener believed that these forces would become effective when applied over many million years. However, most of scholars considered these forces to be totally inadequate. Post-Drift Studies It is interesting to note that for continental drift, most of the evidence was collected from the continental areas in the form of distribution of flora and fauna or deposits like tillite. A number of discoveries during the post-war period added new information to geological literature. Particularly, the information collected from the ocean floor mapping provided new dimensions for the study of distribution of oceans and continents. Convectional Current Theory Arthur Holmes in 1930s discussed the possibility of convection currents operating in the mantle portion. These currents are generated due to radioactive elements causing thermal differences in the mantle portion. Holmes argued that there exists a system of such currents in the entire mantle portion. This was an attempt to provide an explanation to the issue of force, on the basis of which contemporary scientists discarded the continental drift theory. Mapping of the Ocean Floor Detailed research of the ocean configuration revealed that the ocean floor is not just a vast plain but it is full of relief. Expeditions to map the oceanic floor in the post-war period provided a detailed picture of the ocean relief and indicated the existence of submerged

32

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

mountain ranges as well as deep trenches, mostly located closer to the continent margins. The mid-oceanic ridges were found to be most active in terms of volcanic eruptions. The dating of the rocks from the oceanic crust revealed the fact that the latter is much younger than the continental areas. Rocks on either side of the crest of oceanic ridges and having equidistant locations from the crest were found to have remarkable similarities both in terms of their constituents and their age. Ocean Floor Configuration In this section we shall note a few things related to the ocean floor configuration that help us in the understanding of the distribution of continents and oceans. You will be studying the details of ocean floor relief in Chapter 13. The ocean floor may be segmented into three major divisions based on the depth as well as the forms of relief. These divisions are continental margins, deep-sea basins and mid-ocean ridges.

Figure 4.1 : Ocean Floor

Continental Margins These form the transition between continental shores and deep-sea basins. They include continental shelf, continental slope, continental rise and deep-oceanic trenches. Of these, the deep-sea trenches are the areas which are of considerable interest in so far as the distribution of oceans and continents is concerned.

Abyssal Plains These are extensive plains that lie between the continental margins and mid-oceanic ridges. The abyssal plains are the areas where the continental sediments that move beyond the margins get deposited. Mid-Oceanic Ridges This forms an interconnected chain of mountain system within the ocean. It is the longest mountain-chain on the surface of the earth though submerged under the oceanic waters. It is characterised by a central rift system at the crest, a fractionated plateau and flank zone all along its length. The rift system at the crest is the zone of intense volcanic activity. In the previous chapter, you have been introduced to this type of volcanoes as midoceanic volcanoes. Distribution of Earthquakes and Volcanoes Study the maps showing the distribution of seismic activity and volcanoes given in Figure 4.2. You will notice a line of dots in the central parts of the Atlantic Ocean almost parallel to the coastlines. It further extends into the Indian Ocean. It bifurcates a little south of the Indian subcontinent with one branch moving into East Africa and the other meeting a similar line from Myanmar to New Guiana. You will notice that this line of dots coincides with the midoceanic ridges. The shaded belt showing another area of concentration coincides with the Alpine-Himalayan system and the rim of the Pacific Ocean. In general, the foci of the earthquake in the areas of mid-oceanic ridges are at shallow depths whereas along the Alpine-Himalayan belt as well as the rim of the Pacific, the earthquakes are deep-seated ones. The map of volcanoes also shows a similar pattern. The rim of the Pacific is also called rim of fire due to the existence of active volcanoes in this area.

CONCEPT

OF

SEA FLOOR SPREADING

As mentioned above, the post-drift studies provided considerable information that was not

33

DISTRIBUTION OF OCEANS AND CONTINENTS

Figure 4. 2 : Distribution of earthquakes and volcanoes

available at the time Wegener put forth his concept of continental drift. Particularly, the mapping of the ocean floor and palaeomagnetic studies of rocks from oceanic regions revealed the following facts : (i) It was realised that all along the midoceanic ridges, volcanic eruptions are common and they bring huge amounts of lava to the surface in this area. (ii) The rocks equidistant on either sides of the crest of mid-oceanic ridges show remarkable similarities in terms of period of formation, chemical compositions and magnetic properties. Rocks closer to the mid-oceanic ridges are normal polarity and are the youngest. The age of the rocks increases as one moves away from the crest. (iii) The ocean crust rocks are much younger than the continental rocks. The age of rocks in the oceanic crust is nowhere more than 200 million years old. Some of the continental rock formations are as old as 3,200 million years.

(iv) The sediments on the ocean floor are unexpectedly very thin. Scientists were expecting, if the ocean floors were as old as the continent, to have a complete sequence of sediments for a period of much longer duration. However, nowhere was the sediment column found to be older than 200 million years. (v) The deep trenches have deep-seated earthquake occurrences while in the midoceanic ridge areas, the quake foci have shallow depths. These facts and a detailed analysis of magnetic properties of the rocks on either sides of the mid-oceanic ridge led Hess (1961) to propose his hypothesis, known as the “sea floor spreading”. Hess argued that constant eruptions at the crest of oceanic ridges cause the rupture of the oceanic crust and the new lava wedges into it, pushing the oceanic crust on either side. The ocean floor, thus spreads. The younger age of the oceanic crust as well as the fact that the spreading of one ocean does not cause the shrinking of the other, made Hess

34

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Figure 4. 3 : Sea floor spreading

think about the consumption of the oceanic crust. He further maintained that the ocean floor that gets pushed due to volcanic eruptions at the crest, sinks down at the oceanic trenches and gets consumed. The basic concept of sea floor spreading has been depicted in Figure 4.3.

PLATE TECTONICS Since the advent of the concept of sea floor spreading, the interest in the problem of distribution of oceans and continents was revived. It was in 1967, McKenzie and Parker and also Morgan, independently collected the available ideas and came out with another

The motions of the continents during the past 540 million years. 1. Africa; 2. South America; 3. Antarctica; 4. Australia; 5. India; 6. China; 7. North America; 8. Europe; 9. and 10. Siberia (Emilani, 1992)

Figure 4.4 : Position of continents through geological past

35

DISTRIBUTION OF OCEANS AND CONTINENTS

concept termed Plate Tectonics. A tectonic plate (also called lithospheric plate) is a massive, irregularly-shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plates move horizontally over the asthenosphere as rigid units. The lithosphere includes the crust and top mantle with its thickness range varying between 5-100 km in oceanic parts and about 200 km in the continental areas. A plate may be referred to as the continental plate or oceanic plate depending on which of the two occupy a larger portion of the plate. Pacific plate is largely an oceanic plate whereas the Eurasian plate may be called a continental plate. The theory of plate tectonics proposes that the earth’s lithosphere is divided into seven major and some minor plates. Young Fold Mountain ridges, trenches, and/or faults surround these major plates (Figure 4.5). The major plates are as follows : (i) Antarctica and the surrounding oceanic plate

(ii) North American (with western Atlantic floor separated from the South American plate along the Caribbean islands) plate (iii) South American (with western Atlantic floor separated from the North American plate along the Caribbean islands) plate (iv) Pacific plate (v) India-Australia-New Zealand plate (vi) Africa with the eastern Atlantic floor plate (vii) Eurasia and the adjacent oceanic plate. Some important minor plates are listed below: (i) Cocos plate : Between Central America and Pacific plate (ii) Nazca plate : Between South America and Pacific plate (iii) Arabian plate : Mostly the Saudi Arabian landmass (iv) Philippine plate : Between the Asiatic and Pacific plate

Figure 4.5 : Major and minor plates of the world

36

(v) Caroline plate : Between the Philippine

and Indian plate (North of New Guinea) (vi) Fuji plate : North-east of Australia. These plates have been constantly moving over the globe throughout the history of the earth. It is not the continent that moves as believed by Wegener. Continents are part of a plate and what moves is the plate. Moreover, it may be noted that all the plates, without exception, have moved in the geological past, and shall continue to move in the future period as well. Wegener had thought of all the continents to have initially existed as a super continent in the form of Pangaea. However, later discoveries reveal that the continental masses, resting on the plates, have been wandering all through the geological period, and Pangaea was a result of converging of different continental masses that were parts of one or the other plates. Scientists using the palaeomagnetic data have determined the positions held by each of the present continental landmass in different geological periods. Position of the Indian sub-continent (mostly Peninsular India) is traced with the help of the rocks analysed from the Nagpur area. There are three types of plate boundaries:

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Transform Boundaries Where the crust is neither produced nor destroyed as the plates slide horizontally past each other. Transform faults are the planes of separation generally perpendicular to the midoceanic ridges. As the eruptions do not take all along the entire crest at the same time, there is a differential movement of a portion of the plate away from the axis of the earth. Also, the rotation of the earth has its effect on the separated blocks of the plate portions. How do you think the rate of plate movement is determined?

Rates of Plate Movement The strips of normal and reverse magnetic field that parallel the mid-oceanic ridges help scientists determine the rates of plate movement. These rates vary considerably. The Arctic Ridge has the slowest rate (less than 2.5 cm/yr), and the East Pacific Rise near Easter Island, in the South Pacific about 3,400 km west of Chile, has the fastest rate (more than 15 cm/yr). Force for the Plate Movement

Divergent Boundaries Where new crust is generated as the plates pull away from each other. The sites where the plates move away from each other are called spreading sites. The best-known example of divergent boundaries is the Mid-Atlantic Ridge. At this, the American Plate(s) is/are separated from the Eurasian and African Plates. Convergent Boundaries Where the crust is destroyed as one plate dived under another. The location where sinking of a plate occurs is called a subduction zone. There are three ways in which convergence can occur. These are: (i) between an oceanic and continental plate; (ii) between two oceanic plates; and (iii) between two continental plates.

At the time that Wegener proposed his theory of continental drift, most scientists believed that the earth was a solid, motionless body. However, concepts of sea floor spreading and the unified theory of plate tectonics have emphasised that both the surface of the earth and the interior are not static and motionless but are dynamic. The fact that the plates move is now a well-accepted fact. The mobile rock beneath the rigid plates is believed to be moving in a circular manner. The heated material rises to the surface, spreads and begins to cool, and then sinks back into deeper depths. This cycle is repeated over and over to generate what scientists call a convection cell or convective flow. Heat within the earth comes from two main sources: radioactive decay and residual heat. Arthur Holmes first considered

37

DISTRIBUTION OF OCEANS AND CONTINENTS

this idea in the 1930s, which later influenced Harry Hess’ thinking about seafloor spreading. The slow movement of hot, softened mantle that lies below the rigid plates is the driving force behind the plate movement.

MOVEMENT

OF THE

INDIAN PLATE

The Indian plate includes Peninsular India and the Australian continental portions. The subduction zone along the Himalayas forms the northern plate boundary in the form of continent— continent convergence. In the east, it extends through Rakinyoma Mountains of Myanmar towards the island arc along the Java T rench. The eastern margin is a spreading site lying to the east of Australia in the form of an oceanic ridge in SW Pacific. The Western margin follows Kirthar Mountain of Pakistan. It further extends along the Makrana coast and joins the spreading site from the Red Sea rift southeastward along the Chagos Archipelago. The boundary between India and the Antarctic plate is also marked by oceanic ridge (divergent boundary) running in roughly W-E direction and merging into the spreading site, a little south of New Zealand. India was a large island situated off the Australian coast, in a vast ocean. The Tethys Sea separated it from the Asian continent till about 225 million years ago. India is supposed to have started her northward journey about 200 million years ago at the time when Pangaea broke. India collided with Asia about 40-50 million years ago causing rapid uplift of the Himalayas. The positions of India since about 71 million years till the present are shown in the Figure 4.6. It also shows the position of the Indian subcontinent and the Eurasian plate. About 140 million years before the present, the subcontinent was located as south as 50oS. latitude. The two major plates were separated by the Tethys Sea and the Tibetan block was closer to the Asiatic landmass. During the movement of the Indian

Figure 4.6 : Movement of the Indian plate

plate towards the Asiatic plate, a major event that occurred was the outpouring of lava and formation of the Deccan Traps. This started somewhere around 60 million years ago and continued for a long period of time. Note that the subcontinent was still close to the equator. From 40 million years ago and thereafter, the event of formation of the Himalayas took place. Scientists believe that the process is still continuing and the height of the Himalayas is rising even to this date.

38

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

EXERCISES 1.

Multiple choice questions. (i) Who amongst the following was the first to consider the possibility of Europe, Africa and America having been located side by side. (a) Alfred Wegener

(c) Abraham Ortelius

(b) Antonio Pellegrini

(d) Edmond Hess

(ii) Polar fleeing force relates to: (a) Revolution of the Earth

(c) Rotation of the earth

(b) Gravitation

(d) Tides

(iii) Which one of the following is not a minor plate?

(iv)

(a) Nazca

(c) Philippines

(b) Arabia

(d) Antarctica

Which one of the following facts was not considered by those while discussing the concept of sea floor spreading? (a) Volcanic activity along the mid-oceanic ridges. (b) Stripes of normal and reverse magnetic field observed in rocks of ocean floor. (c) Distribution of fossils in different continents. (d) Age of rocks from the ocean floor.

(v)

Which one of the following is the type of plate boundary of the Indian plate along the Himalayan mountains? (a) Ocean-continent convergence (b) Divergent boundary (c) Transform boundary (d) Continent-continent convergence

2.

3.

Answer the following questions in about 30 words. (i)

What were the forces suggested by Wegener for the movement of the continents?

(ii)

How are the convectional currents in the mantle initiated and maintained?

(iii)

What is the major difference between the transform boundary and the convergent or divergent boundaries of plates?

(iv)

What was the location of the Indian landmass during the formation of the Deccan Traps?

Answer the following questions in about 150 words. (i)

What are the evidences in support of the continental drift theory?

(ii)

Bring about the basic difference between the drift theory and Plate tectonics.

(iii)

What were the major post-drift discoveries that rejuvenated the interest of scientists in the study of distribution of oceans and continents?

Project Work Prepare a collage related to damages caused by an earthquake.

UNIT III LANDFORMS This unit deals with •

Rocks and minerals — major types of rocks and their characteristics

•

Landforms and their evolution

•

Geomorphic processes — weathering, mass wasting, erosion and deposition; soils — formation

CHAPTER

MINERALS

T

he earth is composed of various kinds of elements. These elements are in solid form in the outer layer of the earth and in hot and molten form in the interior. About 98 per cent of the total crust of the earth is composed of eight elements like oxygen, silicon, aluminium, iron, calcium, sodium, potassium and magnesium (Table 5.1), and the rest is constituted by titanium, hydrogen, phosphorous, manganese, sulphur, carbon, nickel and other elements. Table 5.1 : The Major Elements of the Earth’s Crust Sl. No. 1. 2. 3. 4. 5. 6. 7. 8. 9.

Elements Oxygen Silicon Aluminium Iron Calcium Sodium Potassium Magnesium Others

By Weight(%) 46.60 27.72 8.13 5.00 3.63 2.83 2.59 2.09 1.41

The elements in the earth’s crust are rarely found exclusively but are usually combined with other elements to make various substances. These substances are recognised as minerals. Thus, a mineral is a naturally occurring inorganic substance, having an orderly atomic structure and a definite chemical composition and physical properties. A mineral is composed of two or more elements. But, sometimes single element minerals like sulphur, copper, silver, gold, graphite etc. are found.

AND

ROCKS

Though the number of elements making up the lithosphere are limited they are combined in many different ways to make up many varieties of minerals. There are at least 2,000 minerals that have been named and identified in the earth crust; but almost all the commonly occurring ones are related to six major mineral groups that are known as major rock forming minerals. The basic source of all minerals is the hot magma in the interior of the earth. When magma cools, crystals of minerals appear and a systematic series of minerals are formed in sequence to solidify so as to form rocks. Minerals such as coal, petroleum and natural gas are organic substances found in solid, liquid and gaseous forms respectively. A brief information about some important minerals in terms of their nature and physical characteristics is given below :

PHYSICAL CHARACTERISTICS (i) Exter nal crystal for m — deter mined by internal arrangement of the molecules — cubes, octahedrons, hexagonal prisms, etc. (ii) Cleavage — tendency to break in given directions producing relatively plane surfaces — result of internal arrangement of the molecules — may cleave in one or more directions and at any angle to each other.

41

MINERALS AND ROCKS

(iii) Fracture — internal molecular arrangement so complex there are no planes of molecules; the crystal will break in an irregular manner, not along planes of cleavage. (iv) Lustre — appearance of a material without regard to colour; each mineral has a distinctive lustre like metallic, silky, glossy etc. (v) Colour — some minerals have characteristic colour determined by their molecular structure — malachite, azurite, chalcopyrite etc., and some minerals are coloured by impurities. For example, because of impurities quartz may be white, green, red, yellow etc. (vi) Streak — colour of the ground powder of any mineral. It may be of the same colour as the mineral or may differ — malachite is green and gives green streak, fluorite is purple or green but gives a white streak. (vii) Transparency — transparent: light rays pass through so that objects can be seen plainly; translucent — light rays pass through but will get diffused so that objects cannot be seen; opaque — light will not pass at all. (viii) Structure — particular arrangement of the individual crystals; fine, medium or coarse grained; fibrous — separable, divergent, radiating. (ix) Hardness — relative resistance being scratched; ten minerals are selected to measure the degree of hardness from 1-10. They are: 1. talc; 2. gypsum; 3. calcite; 4. fluorite; 5. apatite; 6. feldspar; 7. quartz; 8. topaz; 9. corundum; 10. diamond. Compared to this for example, a fingernail is 2.5 and glass or knife blade is 5.5. (x) Specific gravity — the ratio between the weight of a given object and the weight of an equal volume of water; object weighed in air and then weighed in water and divide weight in air by the difference of the two weights.

SOME THEIR

MAJOR MINERALS CHARACTERISTICS

AND

Feldspar Silicon and oxygen are common elements in all types of feldspar and sodium, potassium, calcium, aluminium etc. are found in specific feldspar variety. Half of the earth’s crust is composed of feldspar. It has light cream to salmon pink colour. It is used in ceramics and glass making. Quartz It is one of the most important components of sand and granite. It consists of silica. It is a hard mineral virtually insoluble in water. It is white or colourless and used in radio and radar. It is one of the most important components of granite. Pyroxene Pyroxene consists of calcium, aluminum, magnesium, iron and silica. Pyroxene forms 10 per cent of the earth’s crust. It is commonly found in meteorites. It is in green or black colour. Amphibole Aluminium, calcium, silica, iron, magnesium are the major elements of amphiboles. They form 7 per cent of the earth’s crust. It is in green or black colour and is used in asbestos industry. Hornblende is another form of amphiboles. Mica It comprises of potassium, aluminium, magnesium, iron, silica etc. It forms 4 per cent of the earth’s crust. It is commonly found in igneous and metamorphic rocks. It is used in electrical instruments. Olivine Magnesium, iron and silica are major elements of olivine. It is used in jewellery. It is usually a greenish crystal, often found in basaltic rocks. Besides these main minerals, other minerals like chlorite, calcite, magnetite, haematite, bauxite and barite are also present in some quantities in the rocks.

42

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Metallic Minerals

Igneous Rocks

These minerals contain metal content and can be sub-divided into three types: (i) Precious metals : gold, silver, platinum etc. (ii) Ferrous metals : iron and other metals often mixed with iron to form various kinds of steel. (iii) Non-ferrous metals : include metals like copper, lead, zinc, tin, aluminium etc.

As igneous rocks form out of magma and lava from the interior of the earth, they are known as primary rocks. The igneous rocks (Ignis – in Latin means ‘Fire’) are formed when magma cools and solidifies. You already know what magma is. When magma in its upward movement cools and turns into solid form it is called igneous rock. The process of cooling and solidification can happen in the earth’s crust or on the surface of the earth. Igneous rocks are classified based on texture. Texture depends upon size and arrangement of grains or other physical conditions of the materials. If molten material is cooled slowly at great depths, mineral grains may be very large. Sudden cooling (at the surface) results in small and smooth grains. Intermediate conditions of cooling would result in intermediate sizes of grains making up igneous rocks. Granite, gabbro, pegmatite, basalt, volcanic breccia and tuff are some of the examples of igneous rocks.

Non-Metallic Minerals These minerals do not contain metal content. Sulphur, phosphates and nitrates are examples of non-metallic minerals. Cement is a mixture of non-metallic minerals.

ROCKS The earth’s crust is composed of rocks. A rock is an aggregate of one or more minerals. Rock may be hard or soft and in varied colours. For example, granite is hard, soapstone is soft. Gabbro is black and quartzite can be milky white. Rocks do not have definite composition of mineral constituents. Feldspar and quartz are the most common minerals found in rocks. Petrology is science of rocks. A petrologist studies rocks in all their aspects viz., mineral composition, texture, structure, origin, occurrence, alteration and relationship with other rocks.

As there is a close relation between rocks and landforms, rocks and soils, a geographer requires basic knowledge of rocks. There are many different kinds of rocks which are grouped under three families on the basis of their mode of formation. They are: (i) Igneous Rocks — solidified from magma and lava; (ii) Sedimentary Rocks — the result of deposition of fragments of rocks by exogenous processes; (iii) Metamorphic Rocks — formed out of existing rocks undergoing recrystallisation.

Sedimentary Rocks The word ‘sedimentary’ is derived from the Latin word sedimentum, which means settling. Rocks (igneous, sedimentary and metamorphic) of the earth’s surface are exposed to denudational agents, and are broken up into various sizes of fragments. Such fragments are transported by different exogenous agencies and deposited. These deposits through compaction turn into rocks. This process is called lithification. In many sedimentary rocks, the layers of deposits retain their characteristics even after lithification. Hence, we see a number of layers of varying thickness in sedimentary rocks like sandstone, shale etc. Depending upon the mode of formation, sedimentary rocks are classified into three major groups: (i) mechanically formed — sandstone, conglomerate, limestone, shale, loess etc. are examples; (ii) organically formed — geyserite, chalk, limestone, coal etc. are some examples; (iii) chemically formed — chert, limestone, halite, potash etc. are some examples.

43

MINERALS AND ROCKS

Metamorphic Rocks The word metamorphic means ‘change of form’. These rocks form under the action of pressure, volume and temperature (PVT) changes. Metamorphism occurs when rocks are forced down to lower levels by tectonic processes or when molten magma rising through the crust comes in contact with the crustal rocks or the underlying rocks are subjected to great amounts of pressure by overlying rocks. Metamorphism is a process by which already consolidated rocks undergo recrystallisation and reorganisation of materials within original rocks. Mechanical disruption and reorganisation of the original minerals within rocks due to breaking and crushing without any appreciable chemical changes is called dynamic metamorphism. The materials of rocks chemically alter and recrystallise due to thermal metamorphism. There are two types of thermal metamorphism — contact metamorphism and regional metamorphism. In contact metamorphism the rocks come in contact with hot intruding magma and lava and the rock materials recrystallise under high temperatures. Quite often new materials form out of magma or lava are added to the rocks. In regional metamorphism, rocks undergo recrystallisation due to deformation caused by tectonic shearing together with high temperature or pressure or both. In the process of metamorphism in some rocks grains or minerals get arranged in layers or lines. Such an arrangement of minerals or grains in metamorphic rocks is called foliation or lineation. Sometimes minerals or materials of different groups are arranged into alternating thin to thick layers appearing in light and dark shades. Such a structure in metamorphic rocks is called banding and rocks displaying banding are called banded rocks. Types of metamorphic rocks depend upon original rocks that were subjected to metamorphism. Metamorphic rocks are classified into two

major groups — foliated rocks and non-foliated rocks. Gneissoid, granite, syenite, slate, schist, marble, quartzite etc. are some examples of metamorphic rocks.

ROCK CYCLE Rocks do not remain in their original form for long but may undergo transformation. Rock cycle is a continuous process through which old rocks are transformed into new ones. Igneous rocks are primary rocks and other rocks (sedimentary and metamorphic) form from these primary rocks. Igneous rocks can be changed into metamorphic rocks. The fragments derived out of igneous and metamorphic rocks form into sedimentary

Fig 5.1 : Rock Cycle

rocks. Sedimentary rocks themselves can turn into fragments and the fragments can be a source for formation of sedimentary rocks. The crustal rocks (igneous, metamorphic and sedimentary) once formed may be carried down into the mantle (interior of the earth) through subduction process (parts or whole of crustal plates going down under another plate in zones of plate convergence) and the same melt down due to increase in temperature in the interior and turn into molten magma, the original source for igneous rocks (Figure 5.1).

44

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

EXERCISES 1.

Multiple choice questions. (i) Which one of the following are the two main constituents of granite? (a) Iron and nickel

(c) Silica and aluminium

(b) Iron and silver

(d) Iron Oxide and potassium

(ii) Which one of the following is the salient feature of metamorphic rocks? (a) Changeable

(c) Crystalline

(b) Quite

(d) Foliation

(iii) Which one of the following is not a single element mineral? (a) Gold (b) Silver

(c) Mica (d) Graphite

(iv) Which one of the following is the hardest mineral?

(v)

2.

(c) Quartz

(b) Diamond

(d) Feldspar

Which one of the following is not a sedimentary rock? (a) Tillite

(c) Breccia

(b) Borax

(d) Marble

Answer the following questions in about 30 words. (i)

3.

(a) Topaz

What do you mean by rocks? Name the three major classes of rocks.

(ii)

What is an igneous rock? Describe the method of formation and characteristics of igneous rock.

(iii)

What is meant by sedimentary rock? Describe the mode of formation of sedimentary rock.

(iv)

What relationship explained by rock cycle between the major type of rock?

Answer the following questions in about 150 words. (i)

Define the term ‘mineral’ and name the major classes of minerals with their physical characteristics.

(ii)

Describe the nature and mode of origin of the chief types of rock at the earth’s crust. How will you distinguish them?

(iii)

What are metamorphic rocks? Describe the types of metamorphic rock and how are they formed?

Project Work Collect different rock samples and try to recognise them from their physical characteristics and identify their family.

CHAPTER

GEOMORPHIC PROCESSES

A

fter learning about how the earth was born, how it evolved its crust and other inner layers, how its crustal plates moved and are moving, and other information on earthquakes, the forms of volcanism and about the rocks and minerals the crust is composed of, it is time to know in detail about the surface of the earth on which we live. Let us start with this question. Why is the surface of the earth uneven?

First of all, the earth’s crust is dynamic. You are well aware that it has moved and moves vertically and horizontally. Of course, it moved a bit faster in the past than the rate at which it is moving now. The differences in the internal forces operating from within the earth which built up the crust have been responsible for the variations in the outer surface of the crust. The earth’s surface is being continuously subjected to external forces induced basically by energy (sunlight). Of course, the internal forces are still active though with different intensities. That means, the earth’s surface is being continuously subjected to by external forces originating within the earth’s atmosphere and by internal forces from within the earth. The external forces are known as exogenic forces and the internal forces are known as endogenic forces. The actions of exogenic forces result in wearing down (degradation) of relief/elevations and filling up (aggradation) of basins/depressions, on the earth’s surface. The phenomenon of wearing down of relief variations of the surface of the earth through erosion is known as gradation. The endogenic

forces continuously elevate or build up parts of the earth’s surface and hence the exogenic processes fail to even out the relief variations of the surface of the earth. So, variations remain as long as the opposing actions of exogenic and endogenic forces continue. In general terms, the endogenic forces are mainly land building forces and the exogenic processes are mainly land wearing forces. The surface of the earth is sensitive. Humans depend on it for their sustenance and have been using it extensively and intensively. So, it is essential to understand its nature in order to use it effectively without disturbing its balance and diminishing its potential for the future. Almost all organisms contribute to sustain the earth’s environment. However, humans have caused over use of resources. Use we must, but must also leave it potential enough to sustain life through the future. Most of the surface of the earth had and has been shaped over very long periods of time (hundreds and thousands of years) and because of its use and misuse by humans its potential is being diminished at a fast rate. If the processes which shaped and are shaping the surface of the earth into varieties of forms (shapes) and the nature of materials of which it is composed of, are understood, precautions can be taken to minimise the detrimental effects of human use and to preserve it for posterity.

GEOMORPHIC PROCESSES You would like to know the meaning of geomorphic processes. The endogenic and exogenic forces causing physical stresses and chemical actions on earth materials and

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

bringing about changes in the configuration of the surface of the earth are known as geomorphic processes. Diastrophism and volcanism are endogenic geomorphic processes. These have already been discussed in brief in the preceding unit. Weathering, mass wasting, erosion and deposition are exogenic geomorphic processes. These exogenic processes are dealt with in detail in this chapter. Any exogenic element of nature (like water, ice, wind, etc.,) capable of acquiring and transporting earth materials can be called a geomorphic agent. When these elements of nature become mobile due to gradients, they remove the materials and transport them over slopes and deposit them at lower level. Geomorphic processes and geomorphic agents especially exogenic, unless stated separately, are one and the same. A process is a force applied on earth materials affecting the same. An agent is a mobile medium (like running water, moving ice masses, wind, waves and currents etc.) which removes, transports and deposits earth materials. Running water, groundwater, glaciers, wind, waves and currents, etc., can be called geomorphic agents. Do you think it is essential to distinguish geomorphic agents and geomorphic processes?

Gravity besides being a directional force activating all downslope movements of matter also causes stresses on the earth’s materials. Indirect gravitational stresses activate wave and tide induced currents and winds. Without gravity and gradients there would be no mobility and hence no erosion, transportation and deposition are possible. So, gravitational stresses are as important as the other geomorphic processes. Gravity is the force that is keeping us in contact with the surface and it is the force that switches on the movement of all surface material on earth. All the movements either within the earth or on the surface of the earth occur due to gradients — from higher levels to lower levels, from high pressure to low pressure areas etc.

ENDOGENIC PROCESSES The energy emanating from within the earth is the main force behind endogenic geomorphic processes. This energy is mostly generated by radioactivity, rotational and tidal friction and primordial heat from the origin of the earth. This energy due to geothermal gradients and heat flow from within induces diastrophism and volcanism in the lithosphere. Due to variations in geothermal gradients and heat flow from within, crustal thickness and strength, the action of endogenic forces are not uniform and hence the tectonically controlled original crustal surface is uneven. Diastrophism All processes that move, elevate or build up portions of the earth’s crust come under diastrophism. They include: (i) orogenic processes involving mountain building through severe folding and affecting long and narrow belts of the earth’s crust; (ii) epeirogenic processes involving uplift or warping of large parts of the earth’s crust; (iii) earthquakes involving local relatively minor movements; (iv) plate tectonics involving horizontal movements of crustal plates. In the process of orogeny, the crust is severely deformed into folds. Due to epeirogeny, there may be simple deformation. Orogeny is a mountain building process whereas epeirogeny is continental building process. Through the processes of orogeny, epeirogeny, earthquakes and plate tectonics, there can be faulting and fracturing of the crust. All these processes cause pressure, volume and temperature (PVT) changes which in turn induce metamorphism of rocks. Epeirogeny and orogeny, cite the differences.

Volcanism Volcanism includes the movement of molten rock (magma) onto or toward the earth’s surface and also formation of many intrusive and extrusive volcanic forms. Many aspects of volcanism have already been dealt in detail

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GEOMORPHIC PROCESSES

under volcanoes in the Unit II and under igneous rocks in the preceding chapter in this unit. What do the words volcanism and volcanoes indicate?

EXOGENIC PROCESSES The exogenic processes derive their energy from atmosphere determined by the ultimate energy from the sun and also the gradients created by tectonic factors.

processes and their respective driving forces. It should become clear from this chart that for each process there exists a distinct driving force or energy. As there are different climatic regions on the earth’s surface owing to thermal gradients created by latitudinal, seasonal and land and water spread variations, the exogenic geomorphic processes vary from region to region. The density, type and distribution of vegetation which largely depend upon

Why do you think that the slopes or gradients are created by tectonic factors?

Gravitational force acts upon all earth materials having a sloping surface and tend to produce movement of matter in down slope direction. Force applied per unit area is called stress. Stress is produced in a solid by pushing or pulling. This induces deformation. Forces acting along the faces of earth materials are shear stresses (separating forces). It is this stress that breaks rocks and other earth materials. The shear stresses result in angular displacement or slippage. Besides the gravitational stress earth materials become subjected to molecular stresses that may be caused by a number of factors amongst which temperature changes, crystallisation and melting are the most common. Chemical processes normally lead to loosening of bonds between grains, dissolving of soluble minerals or cementing materials. Thus, the basic reason that leads to weathering, mass movements, erosion and deposition is development of stresses in the body of the earth materials. As there are different climatic regions on the earth’s surface the exogenic geomorphic processes vary from region to region. Temperature and precipitation are the two important climatic elements that control various processes. All the exogenic geomorphic processes are covered under a general term, denudation. The word ‘denude’ means to strip off or to uncover. Weathering, mass wasting/movements, erosion and transportation are included in denudation. The flow chart (Figure 6.1) gives the denudation

Figure 6.1 : Denudational processes and their driving forces

precipitation and temperature exert influence indirectly on exogenic geomorphic processes. Within different climatic regions there may be local variations of the effects of different climatic elements due to altitudinal differences, aspect variations and the variation in the amount of insolation received by north and south facing slopes as compared to east and west facing slopes. Further, due to differences in wind velocities and directions, amount and kind of precipitation, its intensity, the relation between precipitation and evaporation, daily range of temperature, freezing and thawing frequency, depth of frost penetration, the geomorphic processes vary within any climatic region. What is the sole driving force behind all the exogenic processes?

Climatic factors being equal, the intensity of action of exogenic geomorphic processes depends upon type and structure of rocks. The term structure includes such aspects of rocks as folds, faults, orientation and inclination of beds, presence or absence of joints, bedding planes, hardness or softness of constituent minerals, chemical susceptibility of mineral constituents; the permeability or impermeability

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

etc. Different types of rocks with differences in their structure offer varying resistances to various geomorphic processes. A particular rock may be resistant to one process and nonresistant to another. And, under varying climatic conditions, particular rocks may exhibit different degrees of resistance to geomorphic processes and hence they operate at differential rates and give rise to differences in topography. The effects of most of the exogenic geomorphic processes are small and slow and may be imperceptible in a short time span, but will in the long run affect the rocks severely due to continued fatigue. Finally, it boils down to one fact that the differences on the surface of the earth though originally related to the crustal evolution continue to exist in some form or the other due to differences in the type and structure of earth materials, differences in geomorphic processes and in their rates of operation. Some of the exogenic geomorphic processes have been dealt in detail here.

WEATHERING Weathering is action of elements of weather and climate over earth materials. There are a number of processes within weathering which act either individually or together to affect the earth materials in order to reduce them to fragmental state. Weathering is defined as mechanical disintegration and chemical decomposition of rocks through the actions of various elements of weather and climate.

As very little or no motion of materials takes place in weathering, it is an in-situ or on-site process. Is this little motion which can occur sometimes due to weathering synonymous with transportation? If not, why?

Weathering processes are conditioned by many complex geological, climatic, topographic and vegetative factors. Climate is of particular importance. Not only weathering processes differ from climate to climate, but also the depth of the weathering mantle (Figure 6.2).

Figure 6.2 : Climatic regimes and depth of weathering mantles (adapted and modified from Strakhov, 1967)

Activity Mark the latitude values of different climatic regimes in Figure 6.2 and compare the details.

There are three major groups of weathering processes : (i) chemical; (ii) physical or mechanical; (iii) biological weathering processes. Very rarely does any one of these processes ever operate completely by itself, but quite often a dominance of one process can be seen. Chemical Weathering Processes A group of weathering processes viz; solution, carbonation, hydration, oxidation and reduction act on the rocks to decompose, dissolve or reduce them to a fine clastic state through chemical reactions by oxygen, surface and/or soil water and other acids. Water and air (oxygen and carbon dioxide) along with heat must be present to speed up all chemical reactions. Over and above the carbon dioxide present in the air, decomposition of plants and animals increases the quantity of carbon dioxide underground. These chemical reactions on various minerals are very much similar to the chemical reactions in a laboratory. Solution When something is dissolved in water or acids, the water or acid with dissolved contents is

49

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called solution. This process involves removal of solids in solution and depends upon solubility of a mineral in water or weak acids. On coming in contact with water many solids disintegrate and mix up as suspension in water. Soluble rock forming minerals like nitrates, sulphates, and potassium etc. are affected by this process. So, these minerals are easily leached out without leaving any residue in rainy climates and accumulate in dry regions. Minerals like calcium carbonate and calcium magnesium bicarbonate present in limestones are soluble in water containing carbonic acid (formed with the addition of carbon dioxide in water), and are carried away in water as solution. Carbon dioxide produced by decaying organic matter along with soil water greatly aids in this reaction. Common salt (sodium chloride) is also a rock forming mineral and is susceptible to this process of solution. Carbonation Carbonation is the reaction of carbonate and bicarbonate with minerals and is a common process helping the breaking down of feldspars and carbonate minerals. Carbon dioxide from the atmosphere and soil air is absorbed by water, to form carbonic acid that acts as a weak acid. Calcium carbonates and magnesium carbonates are dissolved in carbonic acid and are removed in a solution without leaving any residue resulting in cave formation. Why are clay minerals easily erodible?

Many clay minerals swell and contract during wetting and drying and a repetition of this process results in cracking of overlying materials. Salts in pore spaces undergo rapid and repeated hydration and help in rock fracturing. The volume changes in minerals due to hydration will also help in physical weathering through exfoliation and granular disintegration. Oxidation and Reduction In weathering, oxidation means a combination of a mineral with oxygen to form oxides or hydroxides. Oxidation occurs where there is ready access to the atmosphere and oxygenated waters. The minerals most commonly involved in this process are iron, manganese, sulphur etc. In the process of oxidation rock breakdown occurs due to the disturbance caused by addition of oxygen. Red colour of iron upon oxidation turns to brown or yellow. When oxidised minerals are placed in an environment where oxygen is absent, reduction takes place. Such conditions exist usually below the water table, in areas of stagnant water and waterlogged ground. Red colour of iron upon reduction turns to greenish or bluish grey. These weathering processes are interrelated. Hydration, carbonation and oxidation go hand in hand and hasten the weathering process. Can we give iron rusting as an example of oxidation? How essential is water in chemical weathering processes? Can chemical weathering processes dominate in water scarce hot deserts?

Hydration Hydration is the chemical addition of water. Minerals take up water and expand; this expansion causes an increase in the volume of the material itself or rock. Calcium sulphate takes in water and turns to gypsum, which is more unstable than calcium sulphate. This process is reversible and long, continued repetition of this process causes fatigue in the rocks and may lead to their disintegration.

Physical Weathering Processes Physical or mechanical weathering processes depend on some applied forces. The applied forces could be: (i) gravitational forces such as overburden pressure, load and shearing stress; (ii) expansion forces due to temperature changes, crystal growth or animal activity; (iii) water pressures controlled by wetting and

50

drying cycles. Many of these forces are applied both at the surface and within different earth materials leading to rock fracture. Most of the physical weathering processes are caused by thermal expansion and pressure release. These processes are small and slow but can cause great damage to the rocks because of continued fatigue the rocks suffer due to repetition of contraction and expansion. Unloading and Expansion Removal of overlying rock load because of continued erosion causes vertical pressure release with the result that the upper layers of the rock expand producing disintegration of rock masses. Fractures will develop roughly parallel to the ground surface. In areas of curved ground surface, arched fractures tend to produce massive sheets or exfoliation slabs of rock. Exfoliation sheets resulting from expansion due to unloading and pressure release may measure hundreds or even thousands of metres in horizontal extent. Large, smooth rounded domes called exfoliation domes (Figure 6.3) result due to this process.

Figure 6.3 : A large exfoliation dome in granite rock near bhongir (Bhuvanagiri) town in Andhra Pradesh

Temperature Changes and Expansion Various minerals in rocks possess their own limits of expansion and contraction. With rise in temperature, every mineral expands and pushes against its neighbour and as temperature falls, a corresponding contraction takes place. Because of diurnal changes in the

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

temperatures, this internal movement among the mineral grains of the superficial layers of rocks takes place regularly. This process is most effective in dry climates and high elevations where diurnal temperature changes are drastic. As has been mentioned earlier though these movements are very small they make the rocks weak due to continued fatigue. The surface layers of the rocks tend to expand more than the rock at depth and this leads to the formation of stress within the rock resulting in heaving and fracturing parallel to the surface. Due to differential heating and resulting expansion and contraction of surface layers and their subsequent exfoliation from the surface results in smooth rounded surfaces in rocks. In rocks like granites, smooth surfaced and rounded small to big boulders called tors form due to such exfoliation. What is the difference between exfoliation domes and exfoliated tors?

Freezing, Thawing and Frost Wedging Frost weathering occurs due to growth of ice within pores and cracks of rocks during repeated cycles of freezing and melting. This process is most effective at high elevations in mid-latitudes where freezing and melting is often repeated. Glacial areas are subject to frost wedging daily. In this process, the rate of freezing is important. Rapid freezing of water causes its sudden expansion and high pressure. The resulting expansion affects joints, cracks and small inter granular fractures to become wider and wider till the rock breaks apart. Salt Weathering Salts in rocks expand due to thermal action, hydration and crystallisation. Many salts like calcium, sodium, magnesium, potassium and barium have a tendency to expand. Expansion of these salts depends on temperature and their thermal properties. High temperature ranges between 30 and 50 oC of surface temperatures in deserts favour such salt expansion. Salt crystals in near-surface pores

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cause splitting of individual grains within rocks, which eventually fall off. This process of falling off of individual grains may result in granular disintegration or granular foliation. Salt crystallisation is most effective of all salt-weathering processes. In areas with alternating wetting and drying conditions salt crystal growth is favoured and the neighbouring grains are pushed aside. Sodium chloride and gypsum crystals in desert areas heave up overlying layers of materials and with the result polygonal cracks develop all over the heaved surface. With salt crystal growth, chalk breaks down most readily, followed by limestone, sandstone, shale, gneiss and granite etc.

BIOLOGICAL ACTIVITY

AND

WEATHERING

Biological weathering is contribution to or removal of minerals and ions from the weathering environment and physical changes due to growth or movement of organisms. Burrowing and wedging by organisms like earthworms, termites, rodents etc., help in exposing the new surfaces to chemical attack and assists in the penetration of moisture and air. Human beings by disturbing vegetation, ploughing and cultivating soils, also help in mixing and creating new contacts between air, water and minerals in the earth materials. Decaying plant and animal matter help in the production of humic, carbonic and other acids which enhance decay and solubility of some elements. Algae utilise mineral nutrients for growth and help in concentration of iron and manganese oxides. Plant roots exert a tremendous pressure on the earth materials mechanically breaking them apart.

SOME SPECIAL EFFECTS

OF

WEATHERING

This has already been explained under physical weathering processes of unloading, thermal contraction and expansion and salt weathering. Exfoliation is a result but not a process. Flaking off of more or less curved sheets of shells from over rocks or bedrock results in smooth and rounded surfaces (Figure 6.4). Exfoliation can occur due to expansion and contraction induced by

Fig.6.4 : Exfoliation (Flacking) and granular disintegration

temperature changes. Exfoliation domes and tors result due to unloading and thermal expansion respectively.

SIGNIFICANCE

OF

WEATHERING

Weathering processes are responsible for breaking down the rocks into smaller fragments and preparing the way for formation of not only regolith and soils, but also erosion and mass movements. Biomes and biodiversity is basically a result of forests (vegetation) and forests depend upon the depth of weathering mantles. Erosion cannot be significant if the rocks are not weathered. That means, weathering aids mass wasting, erosion and reduction of relief and changes in landforms are a consequence of erosion. Weathering of rocks and deposits helps in the enrichment and concentrations of certain valuable ores of iron, manganese, aluminium, copper etc., which are of great importance for the national economy. Weathering is an important process in the formation of soils. When rocks undergo weathering, some materials are removed through chemical or physical leaching by groundwater and thereby the concentration of remaining (valuable) materials increases. Without such a weathering taking place, the concentration of the same valuable material may not be sufficient and economically viable to exploit, process and refine. This is what is called enrichment.

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MASS MOVEMENTS These movements transfer the mass of rock debris down the slopes under the direct influence of gravity. That means, air, water or ice do not carry debris with them from place to place but on the other hand the debris may carry with it air, water or ice. The movements of mass may range from slow to rapid, affecting shallow to deep columns of materials and include creep, flow, slide and fall. Gravity exerts its force on all matter, both bedrock and the products of weathering. So, weathering is not a pre-requisite for mass movement though it aids mass movements. Mass movements are very active over weathered slopes rather than over unweathered materials. Mass movements are aided by gravity and no geomorphic agent like running water, glaciers, wind, waves and currents participate in the process of mass movements. That means mass movements do not come under erosion though there is a shift (aided by gravity) of materials from one place to another. Materials over the slopes have their own resistance to disturbing forces and will yield only when force is greater than the shearing resistance of the materials. Weak unconsolidated materials, thinly bedded rocks, faults, steeply dipping beds, vertical cliffs or steep slopes, abundant precipitation and torrential rains and scarcity of vegetation etc., favour mass movements. Several activating causes precede mass movements. They are : (i) removal of support from below to materials above through natural or artificial means; (ii) increase in gradient and height of slopes; (iii) overloading through addition of materials naturally or by artificial filling; (iv) overloading due to heavy rainfall, saturation and lubrication of slope materials; (v) removal of material or load from over the original slope surfaces; (vi) occurrence of earthquakes, explosions or machinery; (vii) excessive natural seepage; (viii) heavy drawdown of water from lakes, reservoirs and rivers leading to slow outflow of water from under the slopes or river banks; (ix) indiscriminate removal of natural vegetation. Heave (heaving up of soils due to frost growth and other causes), flow and slide are

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

the three forms of movements. Figure 6.5 shows the relationships among different types of mass movements, their relative rates of movement and moisture limits.

Figure 6.5 : Relationships among different types of mass movements, their relative rates of movement and moisture limits (after Whitehead, 2001)

Mass movements can be grouped under three major classes: (i) slow movements; (ii) rapid movements; (iii) landslides. Slow Movements Creep is one type under this category which can occur on moderately steep, soil covered slopes. Movement of materials is extremely slow and imperceptible except through extended observation. Materials involved can be soil or rock debris. Have you ever seen fence posts, telephone poles lean downslope from their vertical position and in their linear alignment? If you have, that is due to the creep effect. Depending upon the type of material involved, several types of creep viz., soil creep, talus creep, rock creep, rock-glacier creep etc., can be identified. Also included in this group is solifluction which involves slow downslope flowing soil mass or fine grained rock debris saturated or lubricated with water. This process is quite common in moist temperate areas where surface melting of deeply frozen ground and long continued rain respectively, occur frequently. When the upper portions get saturated and when the lower parts are impervious to water percolation, flowing occurs in the upper parts.

GEOMORPHIC PROCESSES

Rapid Movements These movements are mostly prevalent in humid climatic regions and occur over gentle to steep slopes. Movement of water-saturated clayey or silty earth materials down low-angle terraces or hillsides is known as earthflow. Quite often, the materials slump making steplike terraces and leaving arcuate scarps at their heads and an accumulation bulge at the toe. When slopes are steeper, even the bedrock especially of soft sedimentary rocks like shale or deeply weathered igneous rock may slide downslope. Another type in this category is mudflow. In the absence of vegetation cover and with heavy rainfall, thick layers of weathered materials get saturated with water and either slowly or rapidly flow down along definite channels. It looks like a stream of mud within a valley. When the mudflows emerge out of channels onto the piedmont or plains, they can be very destructive engulfing roads, bridges and houses. Mudflows occur frequently on the slopes of erupting or recently erupted volcanoes. Volcanic ash, dust and other fragments turn into mud due to heavy rains and flow down as tongues or streams of mud causing great destruction to human habitations. A third type is the debris avalanche, which is more characteristic of humid regions with or without vegetation cover and occurs in narrow tracks on steep slopes. This debris avalanche can be much faster than the mudflow. Debris avalanche is similar to snow avalanche.

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discontinuities in the rock, the degree of weathering and the steepness of the slope. Depending upon the type of movement of materials several types are identified in this category. Slump is slipping of one or several units of rock debris with a backward rotation with respect to the slope over which the movement takes place (Figure 6.6). Rapid rolling or sliding

Figure 6.6 : Slumping of debris with backward rotation

of earth debris without backward rotation of mass is known as debris slide. Debris fall is nearly a free fall of earth debris from a vertical or overhanging face. Sliding of individual rock masses down bedding, joint or fault surfaces is rockslide. Over steep slopes, rock sliding is very fast and destructive. Figure 6.7 shows landslide scars over steep slopes. Slides occur as planar failures along discontinuities like bedding planes that dip steeply. Rock fall is free falling of rock blocks over any steep slope keeping itself away from the slope. Rock falls occur from the superficial layers of the rock

In Andes mountains of South America and the Rockies mountains of North America, there are a few volcanoes which erupted during the last decade and very devastating mudflows occurred down their slopes during eruption as well as after eruption.

Landslides These are known as relatively rapid and perceptible movements. The materials involved are relatively dry. The size and shape of the detached mass depends on the nature of

Figure 6.7 : Landslide scars in Shiwalik Himalayan ranges near river Sarada at India-Nepal border, Uttar Pradesh

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face, an occurrence that distinguishes it from rockslide which affects materials up to a substantial depth. Between mass wasting and mass movements, which term do you feel is most appropriate? Why? Can solifluction be included under rapid flow movements? Why it can be and can’t be?

In our country, debris avalanche and landslides occur very frequently in the Himalayas. There are many reasons for this. One, the Himalayas are tectonically active. They are mostly made up of sedimentary rocks and unconsolidated and semi-consolidated deposits. The slopes are very steep. Compared to the Himalayas, the Nilgiris bordering Tamilnadu, Karnataka, Kerala and the Western Ghats along the west coast are relatively tectonically stable and are mostly made up of very hard rocks; but, still, debris avalanches and landslides occur though not as frequently as in the Himalayas, in these hills. Why? Many slopes are steeper with almost vertical cliffs and escarpments in the Western Ghats and Nilgiris. Mechanical weathering due to temperature changes and ranges is pronounced. They receive heavy amounts of rainfall over short periods. So, there is almost direct rock fall quite frequently in these places along with landslides and debris avalanches.

EROSION

AND

DEPOSITION

Erosion involves acquisition and transportation of rock debris. When massive rocks break into smaller fragments through weathering and any other process, erosional geomorphic agents like running water, groundwater, glaciers, wind and waves remove and transport it to other places depending upon the dynamics of each of these agents. Abrasion by rock debris carried by these geomorphic agents also aids greatly in erosion. By erosion, relief degrades, i.e., the landscape is worn down. That means, though weathering aids

erosion it is not a pre-condition for erosion to take place. Weathering, mass-wasting and erosion are degradational processes. It is erosion that is largely responsible for continuous changes that the earth’s surface is undergoing. As indicated in Figure 6.1, denudational processes like erosion and transportation are controlled by kinetic energy. The erosion and transportation of earth materials is brought about by wind, running water, glaciers, waves and ground water. Of these the first three agents are controlled by climatic conditions. Can you compare the three climatically controlled agents?

They represent three states of matter — gaseous (wind), liquid (running water) and solid (glacier) respectively. The erosion can be defined as “application of the kinetic energy associated with the agent to the surface of the land along which it moves”. Kinetic energy is computed as KE = 1/2 mv2 where ‘m’ is the mass and ‘v’ is the velocity. Hence the energy available to perform work will depend on the mass of the material and the velocity with which it is moving. Obviously then you will find that though the glaciers move at very low velocities due to tremendous mass are more effective as the agents of erosion and wind, being in gaseous state, are less effective. The work of the other two agents of erosionwaves and ground water is not controlled by climate. In case of waves it is the location along the interface of litho and hydro sphere — coastal region — that will determine the work of waves, whereas the work of ground water is determined more by the lithological character of the region. If the rocks are permeable and soluble and water is available only then karst topography develops. In the next chapter we shall be dealing with the landforms produced by each of the agents of erosion. Deposition is a consequence of erosion. The erosional agents loose their velocity and hence energy on gentler slopes and the materials carried by them start to settle themselves. In other words, deposition is not actually the work of any agent. The coarser materials get

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GEOMORPHIC PROCESSES

deposited first and finer ones later. By deposition depressions get filled up. The same erosional agents viz., running water, glaciers, wind, waves and groundwater act as aggradational or depositional agents also. What happens to the surface of the earth due to erosion and deposition is elaborated in the next chapter on landforms and their evolution. There is a shift of materials in mass movements as well as in erosion from one place to the other. So, why can’t both be treated as one and the same? Can there be appreciable erosion without rocks undergoing weathering?

SOIL FORMATION Soil and Soil Contents You see plants growing in soils. You play in the ground and come into contact with soil. You touch and feel soil and soil your clothes while playing. Can you describe it? A pedologist who studies soils defines soil as a collection of natural bodies on the earth’s surface containing living matter and supporting or capable of supporting plants. Soil is a dynamic medium in which many chemical, physical and biological activities go on constantly. Soil is a result of decay, it is also the medium for growth. It is a changing and developing body. It has many characteristics that fluctuate with the seasons. It may be alternatively cold and warm or dry and moist. Biological activity is slowed or stopped if the soil becomes too cold or too dry. Organic matter increases when leaves fall or grasses die. The soil chemistry, the amount of organic matter, the soil flora and fauna, the temperature and the moisture, all change with the seasons as well as with more extended periods of time. That means, soil becomes adjusted to conditions of climate, landform and vegetation and will change internally when these controlling conditions change. Process of Soil Formation Soil formation or pedogenesis depends first on weathering. It is this weathering mantle (depth

of the weathered material) which is the basic input for soil to form. First, the weathered material or transported deposits are colonised by bacteria and other inferior plant bodies like mosses and lichens. Also, several minor organisms may take shelter within the mantle and deposits. The dead remains of organisms and plants help in humus accumulation. Minor grasses and ferns may grow; later, bushes and trees will start growing through seeds brought in by birds and wind. Plant roots penetrate down, burrowing animals bring up particles, mass of material becomes porous and spongelike with a capacity to retain water and to permit the passage of air and finally a mature soil, a complex mixture of mineral and organic products forms. Is weathering solely responsible for soil formation? If not, why?

Pedology is soil science. A pedologist is a soil-scientist.

Soil-forming Factors Five basic factors control the formation of soils: (i) parent material; (ii) topography; (iii) climate; (iv) biological activity; (v) time. In fact soil forming factors act in union and affect the action of one another. Parent Material Parent material is a passive control factor in soil formation. Parent materials can be any insitu or on-site weathered rock debris (residual soils) or transported deposits (transported soils). Soil formation depends upon the texture (sizes of debris) and structure (disposition of individual grains/particles of debris) as well as the mineral and chemical composition of the rock debris/deposits. Nature and rate of weathering and depth of weathering mantle are important consideration under parent materials. There may be differences in soil over similar bedrock and dissimilar bedrocks may have similar soils above them. But when soils are very young and have not matured these show strong links

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with the type of parent rock. Also, in case of some limestone areas, where the weathering processes are specific and peculiar, soils will show clear relation with the parent rock. Topography Topography like parent materials is another passive control factor. The influence of topography is felt through the amount of exposure of a surface covered by parent materials to sunlight and the amount of surface and sub-surface drainage over and through the parent materials. Soils will be thin on steep slopes and thick over flat upland areas. Over gentle slopes where erosion is slow and percolation of water is good, soil formation is very favourable. Soils over flat areas may develop a thick layer of clay with good accumulation of organic matter giving the soil dark colour. In middle latitudes, the south facing slopes exposed to sunlight have different conditions of vegetation and soils and the north facing slopes with cool, moist conditions have some other soils and vegetation. Climate Climate is an important active factor in soil formation. The climatic elements involved in soil development are : (i) moisture in terms of its intensity, frequency and duration of precipitation - evaporation and humidity; (ii) temperature in terms of seasonal and diurnal variations. Precipitation gives soil its moisture content which makes the chemical and biological activities possible. Excess of water helps in the downward transportation of soil components through the soil (eluviation) and deposits the same down below (illuviation). In climates like wet equatorial rainy areas with high rainfall, not only calcium, sodium, magnesium, potassium etc. but also a major part of silica is removed from the soil. Removal of silica from the soil is known as desilication. In dry climates, because of high temperature, evaporation exceeds precipitation and hence ground water is brought up to the surface by capillary action and in the process the water evaporates leaving behind salts in the soil. Such salts form into a crust in the soil known as hardpans. In tropical

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

climates and in areas with intermediate precipitation conditions, calcium carbonate nodules (kanker) are formed. Temperature acts in two ways — increasing or reducing chemical and biological activity. Chemical activity is increased in higher temperatures, reduced in cooler temperatures (with an exception of carbonation) and stops in freezing conditions. That is why, tropical soils with higher temperatures show deeper profiles and in the frozen tundra regions soils contain largely mechanically broken materials. Biological Activity The vegetative cover and organisms that occupy the parent materials from the beginning and also at later stages help in adding organic matter, moisture retention, nitrogen etc. Dead plants provide humus, the finely divided organic matter of the soil. Some organic acids which form during humification aid in decomposing the minerals of the soil parent materials. Intensity of bacterial activity shows up differences between soils of cold and warm climates. Humus accumulates in cold climates as bacterial growth is slow. With undecomposed organic matter because of low bacterial activity, layers of peat develop in sub-arctic and tundra climates. In humid tropical and equatorial climates, bacterial growth and action is intense and dead vegetation is rapidly oxidised leaving very low humus content in the soil. Further, bacteria and other soil organisms take gaseous nitrogen from the air and convert it into a chemical form that can be used by plants. This process is known as nitrogen fixation. Rhizobium, a type of bacteria, lives in the root nodules of leguminous plants and fixes nitrogen beneficial to the host plant. The influence of large animals like ants, termites, earthworms, rodents etc., is mechanical, but, it is nevertheless important in soil formation as they rework the soil up and down. In case of earthworms, as they feed on soil, the texture and chemistry of the soil that comes out of their body changes. Time Time is the third important controlling factor in soil formation. The length of time the soil forming processes operate, determines

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GEOMORPHIC PROCESSES

Is it necessary to separate the process of soil formation and the soil forming control factors? Why are time, topography and parent material considered as passive control factors in soil formation?

maturation of soils and profile development. A soil becomes mature when all soil-forming processes act for a sufficiently long time developing a profile. Soils developing from recently deposited alluvium or glacial till are considered young and they exhibit no horizons or only poorly developed horizons. No specific length of time in absolute terms can be fixed for soils to develop and mature.

EXERCISES 1.

Multiple choice questions. (i) Which one of the following processes is a gradational process? (a) Deposition

(c) Volcanism

(b) Diastrophism

(d) Erosion

(ii) Which one of the following materials is affected by hydration process? (a) Granite

(c) Quartz

(b) Clay

(d) Salts

(iii) Debris avalanche can be included in the category of:

2.

(c) Rapid flow mass movements

(b) Slow flow mass movements

(d) Subsidence

Answer the following questions in about 30 words. (i) (ii)

3.

(a) Landslides

It is weathering that is responsible for bio-diversity on the earth. How? What are mass movements that are real rapid and perceptible? List.

(iii)

What are the various mobile and mighty exogenic geomorphic agents and what is the prime job they perform?

(iv)

Is weathering essential as a pre-requisite in the formation of soils? Why?

Answer the following questions in about 150 words. (i)

“Our earth is a playfield for two opposing groups of geomorphic processes.” Discuss.

(ii)

Exogenic geomorphic processes derive their ultimate energy from the sun’s heat. Explain.

(iii)

Are physical and chemical weathering processes independent of each other? If not, why? Explain with examples.

(iv)

How do you distinguish between the process of soil formation and soilforming factors? What is the role of climate and biological activity as two important control factors in the formation of soils?

Project Work Depending upon the topography and materials around you, observe and record climate, possible weathering process and soil contents and characteristics.

CHAPTER

LANDFORMS

AND THEIR

EVOLUTION

A

fter weathering processes have had their actions on the earth materials making up the surface of the earth, the geomorphic agents like running water, ground water, wind, glaciers, waves perform erosion. It is already known to you that erosion causes changes on the surface of the earth. Deposition follows erosion and because of deposition too, changes occur on the surface of the earth. As this chapter deals with landforms and their evolution first start with the question, what is a landform? In simple words, small to medium tracts or parcels of the earth’s surface are called landforms. If landform is a small to medium sized part of the surface of the earth, what is a landscape? Several related landforms together make up landscapes, (large tracts of earth’s surface). Each landform has its own physical shape, size, materials and is a result of the action of certain geomorphic processes and agent(s). Actions of most of the geomorphic processes and agents are slow, and hence the results take a long time to take shape. Every landform has a beginning. Landforms once formed may change in their shape, size and nature slowly or fast due to continued action of geomorphic processes and agents. Due to changes in climatic conditions and vertical or horizontal movements of landmasses, either the intensity of processes or the processes themselves might change leading to new modifications in the landforms. Evolution here implies stages of transformation of either a part of the earth’s surface from one landform into another or transformation of individual landforms after they are once formed. That

means, each and every landform has a history of development and changes through time. A landmass passes through stages of development somewhat comparable to the stages of life — youth, mature and old age. What are the two important aspects of the evolution of landforms?

The evolutionary history of the continually changing surface of the earth is essential to be understood in order to use it effectively without disturbing its balance and diminishing its potential for the future. Geomorphology deals with the reconstruction of the history of the surface of the earth through a study of its forms, the materials of which it is made up of and the processes that shape it. Changes on the surface of the earth owe mostly to erosion by various geomorphic agents. Of course, the process of deposition too, by covering the land surfaces and filling the basins, valleys or depressions, brings changes in the surface of the land. Deposition follows erosion and the depositional surfaces too are ultimately subjected to erosion. Running water, ground-water, glaciers, wind and waves are powerful erosional and depositional agents shaping and changing the surface of the earth aided by weathering and mass wasting processes. These geomorphic agents acting over long periods of time produce systematic changes leading to sequential development of landforms. Each geomorphic agent produces its own assemblage of landforms. Not only this, each geomorphic process and agent leave their distinct imprints on the landforms they

LANDFORMS AND THEIR EVOLUTION

produce. You know that most of the geomorphic processes are imperceptible functions and can only be seen and measured through their results. What are the results? These results are nothing but landforms and their characteristics. Hence, a study of landforms, will reveal to us the process and agent which has made or has been making those landforms. Most of the geomorphic processes are imperceptible. Cite a few processes which can be seen and a few which can’t be seen.

As the geomorphic agents are capable of erosion and deposition, two sets — erosional or destructional and depositional or constructional — of landforms are produced by them. Many varieties of landforms develop by the action of each of the geomorphic agents depending upon especially the type and structure i.e. folds, faults, joints, fractures, hardness and softness, permeability and impermeability, etc. come under structure of rocks. There are some other independent controls like (i) stability of sea level; (ii) tectonic stability of landmasses; (iii) climate, which influence the evolution of landforms. Any disturbance in any of these three controlling factors can upset the systematic and sequential stages in the development and evolution of landforms. In the following pages, under each of the geomorphic regimes i.e. running water; groundwater, glaciers, waves, and winds, first a brief discussion is presented as to how landmasses are reduced in their relief through erosion and then, development of some of the erosional and depositional landforms is dealt with.

RUNNING WATER In humid regions, which receive heavy rainfall running water is considered the most important of the geomorphic agents in bringing about the degradation of the land surface. There are two components of running water. One is overland flow on general land surface as a sheet. Another is linear flow as

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streams and rivers in valleys. Most of the erosional landforms made by running water are associated with vigorous and youthful rivers flowing along gradients. With time, stream channels over steep gradients turn gentler due to continued erosion, and as a consequence, lose their velocity, facilitating active deposition. There may be depositional forms associated with streams flowing over steep slopes. But these phenomena will be on a small scale compared to those associated with rivers flowing over medium to gentle slopes. The gentler the river channels in gradient or slope, the greater is the deposition. When the stream beds turn gentler due to continued erosion, downward cutting becomes less dominant and lateral erosion of banks increases and as a consequence the hills and valleys are reduced to plains. Is complete reduction of relief of a high land mass possible?

Overland flow causes sheet erosion. Depending upon irregularities of the land surface, the overland flow may concentrate into narrow to wide paths. Because of the sheer friction of the column of flowing water, minor or major quantities of materials from the surface of the land are removed in the direction of flow and gradually small and narrow rills will form. These rills will gradually develop into long and wide gullies; the gullies will further deepen, widen, lengthen and unite to give rise to a network of valleys. In the early stages, down-cutting dominates during which irregularities such as waterfalls and cascades will be removed. In the middle stages, streams cut their beds slower, and lateral erosion of valley sides becomes severe. Gradually, the valley sides are reduced to lower and lower slopes. The divides between drainage basins are likewise lowered until they are almost completely flattened leaving finally, a lowland of faint relief with some low resistant remnants called monadnocks standing out here and there. This type of plain forming as a result of stream erosion is called a peneplain (an almost plain). The characteristics of each of the stages of landscapes developing in running water regimes may be summarised as follows:

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Youth Streams are few during this stage with poor integration and flow over original slopes showing shallow V-shaped valleys with no floodplains or with very narrow floodplains along trunk streams. Streams divides are broad and flat with marshes, swamp and lakes. Meanders if present develop over these broad upland surfaces. These meanders may eventually entrench themselves into the uplands. Waterfalls and rapids may exist where local hard rock bodies are exposed. Mature During this stage streams are plenty with good integration. The valleys are still V-shaped but deep; trunk streams are broad enough to have wider floodplains within which streams may flow in meanders confined within the valley. The flat and broad inter stream areas and swamps and marshes of youth disappear and the stream divides turn sharp. Waterfalls and rapids disappear. Old Smaller tributaries during old age are few with gentle gradients. Streams meander freely over vast floodplains showing natural levees, oxbow lakes, etc. Divides are broad and flat with lakes, swamps and marshes. Most of the landscape is at or slightly above sea level.

Figure 7.1 : The Valley of Kaveri river near Hogenekal, Dharmapuri district, Tamilnadu in the form of gorge

EROSIONAL LANDFORMS Valleys Valleys start as small and narrow rills; the rills will gradually develop into long and wide gullies; the gullies will further deepen, widen and lengthen to give rise to valleys. Depending upon dimensions and shape, many types of valleys like V-shaped valley, gorge, canyon, etc. can be recognised. A gorge is a deep valley with very steep to straight sides (Figure 7.1) and a canyon is characterised by steep step-like side slopes (Figure 7.2) and may be as deep as a gorge. A gorge is almost equal in width at its top as well as its bottom. In contrast, a canyon

Figure 7.2 : An entrenched meander loop of river Colorado in USA showing step-like side slopes of its valley typical of a canyon

is wider at its top than at its bottom. In fact, a canyon is a variant of gorge. Valley types depend upon the type and structure of rocks in which they form. For example, canyons commonly form in horizontal bedded sedimentary rocks and gorges form in hard rocks.

LANDFORMS AND THEIR EVOLUTION

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Potholes and Plunge Pools

River Terraces

Over the rocky beds of hill-streams more or less circular depressions called potholes form because of stream erosion aided by the abrasion of rock fragments. Once a small and shallow depression forms, pebbles and boulders get collected in those depressions and get rotated by flowing water and consequently the depressions grow in dimensions. A series of such depressions eventually join and the stream valley gets deepened. At the foot of waterfalls also, large potholes, quite deep and wide, form because of the sheer impact of water and rotation of boulders. Such large and deep holes at the base of waterfalls are called plunge pools. These pools also help in the deepening of valleys. Waterfalls are also transitory like any other landform and will recede gradually and bring the floor of the valley above waterfalls to the level below.

River terraces are surfaces marking old valley floor or floodplain levels. They may be bedrock surfaces without any alluvial cover or alluvial terraces consisting of stream deposits. River terraces are basically products of erosion as they result due to vertical erosion by the stream into its own depositional floodplain. There can be a number of such terraces at different heights indicating former river bed levels. The river terraces may occur at the same elevation on either side of the rivers in which case they are called paired terraces (Figure 7.3).

INCISED

OR

ENTRENCHED MEANDERS

In streams that flow rapidly over steep gradients, normally erosion is concentrated on the bottom of the stream channel. Also, in the case of steep gradient streams, lateral erosion on the sides of the valleys is not much when compared to the streams flowing on low and gentle slopes. Because of active lateral erosion, streams flowing over gentle slopes, develop sinuous or meandering courses. It is common to find meandering courses over floodplains and delta plains where stream gradients are very gentle. But very deep and wide meanders can also be found cut in hard rocks. Such meanders are called incised or entrenched meanders (Figure 7.2). Meander loops develop over original gentle surfaces in the initial stages of development of streams and the same loops get entrenched into the rocks normally due to erosion or slow, continued uplift of the land over which they start. They widen and deepen over time and can be found as deep gorges and canyons in hard rock areas. They give an indication on the status of original land surfaces over which streams have developed. What are the differences between incised meanders and meanders over flood and delta plains?

Figure 7.3 : Paired and unpaired river terraces

When a terrace is present only on one side of the stream and with none on the other side or one at quite a different elevation on the other side, the terraces are called non-paired terraces. Unpaired terraces are typical in areas of slow uplift of land or where the water column changes are not uniform along both the banks. The terraces may result due to (i) receding water after a peak flow; (ii) change in hydrological regime due to climatic changes; (iii) tectonic uplift of land; (iv) sea level changes in case of rivers closer to the sea.

DEPOSITIONAL LANDFORMS Alluvial Fans Alluvial fans (Figure 7.4) are formed when streams flowing from higher levels break into foot slope plains of low gradient. Normally very coarse load is carried by streams flowing over mountain slopes. This load becomes too heavy for the streams to be carried over gentler

62

gradients and gets dumped and spread as a broad low to high cone shaped deposit called alluvial fan. Usually, the streams which flow over fans are not confined to their original channels for long and shift their position across the fan forming many channels called distributaries. Alluvial fans in humid areas show normally low cones with gentle slope from

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

as a low cone. Unlike in alluvial fans, the deposits making up deltas are very well sorted with clear stratification. The coarsest materials settle out first and the finer fractions like silts and clays are carried out into the sea. As the delta grows, the river distributaries continue to increase in length (Figure 7.5) and delta continues to build up into the sea. Floodplains, Natural Levees and Point Bars

Figure 7.4 : An alluvial fan deposited by a hill stream on the way to Amarnath, Jammu and Kashmir

head to toe and they appear as high cones with steep slope in arid and semi-arid climates. Deltas Deltas are like alluvial fans but develop at a different location. The load carried by the rivers is dumped and spread into the sea. If this load is not carried away far into the sea or distributed along the coast, it spreads and accumulates

Figure 7.5 : A satellite view of part of Krishna river delta, Andhra Pradesh

Deposition develops a floodplain just as erosion makes valleys. Floodplain is a major landform of river deposition. Large sized materials are deposited first when stream channel breaks into a gentle slope. Thus, normally, fine sized materials like sand, silt and clay are carried by relatively slow moving waters in gentler channels usually found in the plains and deposited over the bed and when the waters spill over the banks during flooding above the bed. A river bed made of river deposits is the active floodplain. The floodplain above the bank is inactive floodplain. Inactive floodplain above the banks basically contain two types of deposits — flood deposits and channel deposits. In plains, channels shift laterally and change their courses occasionally leaving cut-off courses which get filled up gradually. Such areas over flood plains built up by abandoned or cut-off channels contain coarse deposits. The flood deposits of spilled waters carry relatively finer materials like silt and clay. The flood plains in a delta are called delta plains. Natural levees and point bars (Figure 7.6) are some of the important landforms found associated with floodplains. Natural levees are found along the banks of large rivers. They are low, linear and parallel ridges of coarse deposits along the banks of rivers, quite often cut into individual mounds. During flooding as the water spills over the bank, the velocity of the water comes down and large sized and high specific gravity materials get dumped in the immediate vicinity of the bank as ridges. They are high nearer the banks and slope gently away from the river. The levee deposits are coarser than the deposits spread by flood waters away from the river. When rivers shift laterally, a series of natural levees can form.

LANDFORMS AND THEIR EVOLUTION

Figure 7.6 : Natural levee and point bars

Point bars are also known as meander bars. They are found on the convex side of meanders of large rivers and are sediments deposited in a linear fashion by flowing waters along the bank. They are almost uniform in profile and in width and contain mixed sizes of sediments. If there more than one ridge, narrow and elongated depressions are found in between the point bars. Rivers build a series of them depending upon the water flow and supply of sediment. As the rivers build the point bars on the convex side, the bank on the concave side will erode actively.

63

Meander is not a landform but is only a type of channel pattern. This is because of (i) propensity of water flowing over very gentle gradients to work laterally on the banks; (ii) unconsolidated nature of alluvial deposits making up the banks with many irregularities which can be used by water exerting pressure laterally; (iii) coriolis force acting on the fluid water deflecting it like it deflects the wind. When the gradient of the channel becomes extremely low, water flows leisurely and starts working laterally. Slight irregularities along the banks slowly get transformed into a small curvature in the banks; the curvature deepens due to deposition on the inside of the curve and erosion along the bank on the outside. If there is no deposition and no erosion or undercutting, the tendency to meander is reduced. Normally, in meanders of large rivers, there is active deposition along the convex bank and undercutting along the concave bank.

In what way do natural levees differ from point bars?

Meanders In large flood and delta plains, rivers rarely flow in straight courses. Loop-like channel patterns called meanders develop over flood and delta plains (Figure 7.7).

Figure 7.7 : A satellite scene showing meandering Burhi Gandak river near Muzaffarpur, Bihar, showing a number of oxbow lakes and cut-offs

Figure 7.8 : Meander growth and cut-off loops and slip-off and undercut banks

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

64

The concave bank is known as cut-off bank which shows up as a steep scarp and the convex bank presents a long, gentle profile and is known as slip-off bank (Figure 7.8). As meanders grow into deep loops, the same may get cut-off due to erosion at the inflection points and are left as ox-bow lakes.

is more in the valley, channel bars and islands of sand, gravel and pebbles develop on the floor of the channel and the water flow is divided into multiple threads. These thread-like streams of water rejoin and subdivide repeatedly to give a typical braided pattern (Figure 7.9).

Braided Channels When rivers carry coarse material, there can be selective deposition of coarser materials causing formation of a central bar which diverts the flow towards the banks; and this flow increases lateral erosion on the banks. As the valley widens, the water column is reduced and more and more materials get deposited as islands and lateral bars developing a number of separate channels of water flow. Deposition and lateral erosion of banks are essential for the for mation of braided patter n. Or, alternatively, when discharge is less and load

Figure 7.9 : Satellite scenes showing braided channel segments of Gandak (left) and Son (right) rivers Arrows show the direction of flow

Figure 7.10 : Various karst features

LANDFORMS AND THEIR EVOLUTION

GROUNDWATER Here the interest is not on groundwater as a resource. Our focus is on the work of groundwater in the erosion of landmasses and evolution of landforms. The surface water percolates well when the rocks are permeable, thinly bedded and highly jointed and cracked. After vertically going down to some depth, the water under the ground flows horizontally through the bedding planes, joints or through the materials themselves. It is this downward and horizontal movement of water which causes the rocks to erode. Physical or mechanical removal of materials by moving groundwater is insignificant in developing landforms. That is why, the results of the work of groundwater cannot be seen in all types of rocks. But in rocks like limestones or dolomites rich in calcium carbonate, the surface water as well as groundwater through the chemical process of solution and precipitation deposition develop varieties of landforms. These two processes of solution and precipitation are active in limestones or dolomites occurring either exclusively or interbedded with other rocks. Any limestone or dolomitic region showing typical landforms produced by the action of groundwater through the processes of solution and deposition is called Karst topography after the typical topography developed in limestone rocks of Karst region in the Balkans adjacent to Adriatic sea. The karst topography is also characterised by erosional and depositional landforms.

EROSIONAL LANDFORMS Pools, Sinkholes, Lapies and Limestone Pavements Small to medium sized round to sub-rounded shallow depressions called swallow holes form on the surface of limestones through solution. Sinkholes are very common in limestone/karst areas. A sinkhole is an opening more or less circular at the top and funnel-shapped towards the bottom with sizes varying in area from a few sq. m to a hectare and with depth from a less than half a metre to thirty metres or more. Some of these form solely through solution action (solution sinks) and others might start

65

as solution forms first and if the bottom of a sinkhole forms the roof of a void or cave underground, it might collapse leaving a large hole opening into a cave or a void below (collapse sinks). Quite often, sinkholes are covered up with soil mantle and appear as shallow water pools. Anybody stepping over such pools would go down like it happens in quicksands in deserts. The term doline is sometimes used to refer the collapse sinks. Solution sinks are more common than collapse sinks. Quite often the surface run-off simply goes down swallow and sink holes and flow as underground streams and re-emerge at a distance downstream through a cave opening. When sink holes and dolines join together because of slumping of materials along their margins or due to roof collapse of caves, long, narrow to wide trenches called valley sinks or Uvalas form. Gradually, most of the surface of the limestone is eaten away by these pits and trenches, leaving it extremely irregular with a maze of points, grooves and ridges or lapies. Especially, these ridges or lapies form due to differential solution activity along parallel to sub-parallel joints. The lapie field may eventually turn into somewhat smooth limestone pavements. Caves In areas where there are alternating beds of rocks (shales, sandstones, quartzites) with limestones or dolomites in between or in areas where limestones are dense, massive and occurring as thick beds, cave formation is prominent. Water percolates down either through the materials or through cracks and joints and moves horizontally along bedding planes. It is along these bedding planes that the limestone dissolves and long and narrow to wide gaps called caves result. There can be a maze of caves at different elevations depending upon the limestone beds and intervening rocks. Caves normally have an opening through which cave streams are discharged. Caves having openings at both the ends are called tunnels. Depositional Landforms Many depositional forms develop within the limestone caves. The chief chemical in limestone

66

is calcium carbonate which is easily soluble in carbonated water (carbon dioxide absorbed rainwater). This calcium carbonate is deposited when the water carrying it in solution evaporates or loses its carbon dioxide as it trickles over rough rock surfaces. Stalactites, Stalagmites and Pillars Stalactites hang as icicles of different diameters. Normally they are broad at their bases and taper towards the free ends showing up in a variety of forms. Stalagmites rise up from the floor of the caves. In fact, stalagmites form due to dripping water from the surface or through the thin pipe, of the stalactite, immediately below it (Figure 7.11).

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

GLACIERS Masses of ice moving as sheets over the land (continental glacier or pidmont glacier if a vast sheet of ice is spread over the plains at the foot of mountains) or as linear flows down the slopes of mountains in broad trough-like valleys (mountain and valley glaciers) are called glaciers (Figure 7.12). The movement of glaciers

Figure 7.12 : A glacier in its valley

is slow unlike water flow. The movement could be a few centimetres to a few metres a day or even less or more. Glaciers move basically because of the force of gravity. We have many glaciers in our country moving down the slopes and valleys in Himalayas. Higher reaches of Uttaranchal, Himachal Pradesh and Jammu and Kashmir, are places to see some of them. Do you know where one can see river Bhagirathi is basically fed by meltwaters from under the snout (Gaumukh) of the Gangotri glacier. In fact, Alkapuri glacier feeds waters to Alakananda river. Rivers Alkananda and Bhagirathi join to make river Ganga near Deoprayag.

Figure 7.11 : Stalactites and stalagmites in a limestone cave

Stalagmites may take the shape of a column, a disc, with either a smooth, rounded bulging end or a miniature crater like depression. The stalagmite and stalactites eventually fuse to give rise to columns and pillars of different diameters.

Erosion by glaciers is tremendous because of friction caused by sheer weight of the ice. The material plucked from the land by glaciers (usually large-sized angular blocks and fragments) get dragged along the floors or sides of the valleys and cause great damage through abrasion and plucking. Glaciers can cause significant damage to even un-weathered rocks and can reduce high mountains into low hills and plains.

LANDFORMS AND THEIR EVOLUTION

As glaciers continue to move, debris gets removed, divides get lowered and eventually the slope is reduced to such an extent that glaciers will stop moving leaving only a mass of low hills and vast outwash plains along with other depositional features. Figures 7.13 and 7.14 show various glacial erosional and depositional forms described in the text.

EROSIONAL LANDFORMS Cirque Cirques are the most common of landforms in glaciated mountains. The cirques quite often are found at the heads of glacial valleys. The accumulated ice cuts these cirques while moving down the mountain tops. They are deep, long and wide troughs or basins with very steep concave to vertically dropping high walls at its head as well as sides. A lake of water can be seen quite often within the cirques after

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the glacier disappears. Such lakes are called cirque or tarn lakes. There can be two or more cirques one leading into another down below in a stepped sequence. Horns and Serrated Ridges Horns form through head ward erosion of the cirque walls. If three or more radiating glaciers cut headward until their cirques meet, high, sharp pointed and steep sided peaks called horns form. The divides between cirque side walls or head walls get narrow because of progressive erosion and turn into serrated or saw-toothed ridges sometimes referred to as arêtes with very sharp crest and a zig-zag outline. The highest peak in the Alps, Matterhorn and the highest peak in the Himalayas, Everest are in fact horns formed through headward erosion of radiating cirques.

Figure 7.13 : Some glacial erosional and depositional forms (adapted and modified from Spencer, 1962)

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

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Glacial Valleys/Troughs Glaciated valleys are trough-like and U-shaped with broad floors and relatively smooth, and steep sides. The valleys may contain littered debris or debris shaped as moraines with swampy appearance. There may be lakes gouged out of rocky floor or formed by debris within the valleys. There can be hanging valleys at an elevation on one or both sides of the main glacial valley. The faces of divides or spurs of such hanging valleys opening into main glacial valleys are quite often truncated to give them an appearance like triangular facets. Very deep glacial troughs filled with sea water and making up shorelines (in high latitudes) are called fjords/fiords. What are the basic differences between glacial valleys and river valleys?

Depositional Landforms The unassorted coarse and fine debris dropped by the melting glaciers is called glacial till. Most of the rock fragments in till are angular to subangular in form. Streams form by melting ice at the bottom, sides or lower ends of glaciers.

Some amount of rock debris small enough to be carried by such melt-water streams is washed down and deposited. Such glaciofluvial deposits are called outwash deposits. Unlike till deposits, the outwash deposits are roughly stratified and assorted. The rock fragments in outwash deposits are somewhat rounded at their edges. Figure 7.14 shows a few depositional landforms commonly found in glaciated areas. Moraines They are long ridges of deposits of glacial till. Terminal moraines are long ridges of debris deposited at the end (toe) of the glaciers. Lateral moraines form along the sides parallel to the glacial valleys. The lateral moraines may join a terminal moraine forming a horse-shoe shaped ridge. There can be many lateral moraines on either side in a glacial valley. These moraines partly or fully owe their origin to glacio-fluvial waters pushing up materials to the sides of glaciers. Many valley glaciers retreating rapidly leave an irregular sheet of till over their valley floors. Such deposits varying greatly in thickness and in surface topography are called ground moraines. The moraine in the centre of the

Figure 7.14 : A panoramic diagram of glacial landscape with various depositional landforms (adapted and modified from Spencer, 1962)

LANDFORMS AND THEIR EVOLUTION

glacial valley flanked by lateral moraines is called medial moraine. They are imperfectly formed as compared to lateral moraines. Sometimes medial moraines are indistinguishable from ground moraines. Eskers When glaciers melt in summer, the water flows on the surface of the ice or seeps down along the margins or even moves through holes in the ice. These waters accumulate beneath the glacier and flow like streams in a channel beneath the ice. Such streams flow over the ground (not in a valley cut in the ground) with ice forming its banks. Very coarse materials like boulders and blocks along with some minor fractions of rock debris carried into this stream settle in the valley of ice beneath the glacier and after the ice melts can be found as a sinuous ridge called esker. Outwash Plains The plains at the foot of the glacial mountains or beyond the limits of continental ice sheets are covered with glacio-fluvial deposits in the form of broad flat alluvial fans which may join to form outwash plains of gravel, silt, sand and clay. Distinguish between river alluvial plains and glacial outwash plains.

Drumlins Drumlins are smooth oval shaped ridge-like features composed mainly of glacial till with some masses of gravel and sand. The long axes of drumlins are parallel to the direction of ice movement. They may measure up to 1 km in length and 30 m or so in height. One end of the drumlins facing the glacier called the stoss end is blunter and steeper than the other end called tail. The drumlins form due to dumping of rock debris beneath heavily loaded ice through fissures in the glacier. The stoss end gets blunted due to pushing by moving ice. Drumlins give an indication of direction of glacier movement.

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What is the difference between till and alluvium?

WAVES

AND

CURRENTS

Coastal processes are the most dynamic and hence most destructive. So, don’t you think it is important to know about the coastal processes and forms? Some of the changes along the coasts take place very fast. At one place, there can be erosion in one season and deposition in another. Most of the changes along the coasts are accomplished by waves. When waves break, the water is thrown with great force onto the shore, and simultaneously, there is a great churning of sediments on the sea bottom. Constant impact of breaking waves drastically affects the coasts. Storm waves and tsunami waves can cause far-reaching changes in a short period of time than normal breaking waves. As wave environment changes, the intensity of the force of breaking waves changes. Do you know about the generating forces behind waves and currents? If not, refer to the chapter on movements in ocean waters.

Other than the action of waves, the coastal landforms depend upon (i) the configuration of land and sea floor; (ii) whether the coast is advancing (emerging) seaward or retreating (submerging) landward. Assuming sea level to be constant, two types of coasts are considered to explain the concept of evolution of coastal landforms: (i) high, rocky coasts (submerged coasts); (ii) low, smooth and gently sloping sedimentary coasts (emerged coasts).

HIGH ROCKY COASTS Along the high rocky coasts, the rivers appear to have been drowned with highly irregular coastline. The coastline appears highly indented with extension of water into the land where glacial valleys (fjords) are present. The hill sides drop off sharply into the water. Shores do not show any depositional landforms initially. Erosion features dominate.

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Along high rocky coasts, waves break with great force against the land shaping the hill sides into cliffs. With constant pounding by waves, the cliffs recede leaving a wave-cut platform in front of the sea cliff. Waves gradually minimise the irregularities along the shore. The materials which fall off, and removed from the sea cliffs, gradually break into smaller fragments and roll to roundness, will get deposited in the offshore. After a considerable period of cliff development and retreat when coastline turns somewhat smooth, with the addition of some more material to this deposit in the offshore, a wave-built terrace would develop in front of wave-cut terrace. As the erosion along the coast takes place a good supply material becomes available to longshore currents and waves to deposit them as beaches along the shore and as bars (long ridges of sand and/or shingle parallel to the coast) in the nearshore zone. Bars are submerged features and when bars show up above water, they are called barrier bars. Barrier bar which get keyed up to the headland of a bay is called a spit. When barrier bars and spits form at the mouth of a bay and block it, a lagoon forms. The lagoons would gradually get filled up by sediments from the land giving rise to a coastal plain.

LOW SEDIMENTARY COASTS Along low sedimentary coasts the rivers appear to extend their length by building coastal plains and deltas. The coastline appears smooth with occasional incursions of water in the form of lagoons and tidal creeks. The land slopes gently into the water. Marshes and swamps may abound along the coasts. Depositional features dominate. When waves break over a gently sloping sedimentary coast, the bottom sediments get churned and move readily building bars, barrier bars, spits and lagoons. Lagoons would eventually turn into a swamp which would subsequently turn into a coastal plain. The maintenance of these depositional features depends upon the steady supply of materials.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Storm and tsunami waves cause drastic changes irrespective of supply of sediments. Large rivers which bring lots of sediments build deltas along low sedimentary coasts. The west coast of our country is a high rocky retreating coast. Erosional forms dominate in the west coast. The east coast of India is a low sedimentary coast. Depositional forms dominate in the east coast.

What are the various differences between a high rocky coast and a low sedimentary coast in terms of processes and landforms?

EROSIONAL LANDFORMS Cliffs, Terraces, Caves and Stacks Wave-cut cliffs and terraces are two forms usually found where erosion is the dominant shore process. Almost all sea cliffs are steep and may range from a few m to 30 m or even more. At the foot of such cliffs there may be a flat or gently sloping platform covered by rock debris derived from the sea cliff behind. Such platforms occurring at elevations above the average height of waves is called a wave-cut terrace. The lashing of waves against the base of the cliff and the rock debris that gets smashed against the cliff along with lashing waves create hollows and these hollows get widened and deepened to form sea caves. The roofs of caves collapse and the sea cliffs recede further inland. Retreat of the cliff may leave some remnants of rock standing isolated as small islands just off the shore. Such resistant masses of rock, originally parts of a cliff or hill are called sea stacks. Like all other features, sea stacks are also temporary and eventually coastal hills and cliffs will disappear because of wave erosion giving rise to narrow coastal plains, and with onrush of deposits from over the land behind may get covered up by alluvium or may get covered up by shingle or sand to form a wide beach.

LANDFORMS AND THEIR EVOLUTION

DEPOSITIONAL LANDFORMS Beaches and Dunes Beaches are characteristic of shorelines that are dominated by deposition, but may occur as patches along even the rugged shores. Most of the sediment making up the beaches comes from land carried by the streams and rivers or from wave erosion. Beaches are temporary features. The sandy beach which appears so permanent may be reduced to a very narrow strip of coarse pebbles in some other season. Most of the beaches are made up of sand sized materials. Beaches called shingle beaches contain excessively small pebbles and even cobbles. Just behind the beach, the sands lifted and winnowed from over the beach surfaces will be deposited as sand dunes. Sand dunes forming long ridges parallel to the coastline are very common along low sedimentary coasts.

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develop attached to headlands/hills. The barriers, bars and spits at the mouth of the bay gradually extend leaving only a small opening of the bay into the sea and the bay will eventually develop into a lagoon. The lagoons get filled up gradually by sediment coming from the land or from the beach itself (aided by wind) and a broad and wide coastal plain may develop replacing a lagoon. Do you know, the coastal off-shore bars offer the first buffer or defence against storm or tsunami by absorbing most of their destructive force. Then come the barriers, beaches, beach dunes and mangroves, if any, to absorb the destructive force of storm and tsunami waves. So, if we do anything which disturbs the ‘sediment budget’ and the mangroves along the coast, these coastal forms will get eroded away leaving human habitations to bear first strike of storm and tsunami waves.

Bars, Barriers and Spits A ridge of sand and shingle formed in the sea in the off-shore zone (from the position of low tide waterline to seaward) lying approximately parallel to the coast is called an off-shore bar. An off-shore bar which is exposed due to further addition of sand is termed a barrier bar. The off-shore bars and barriers commonly form across the mouth of a river or at the entrance of a bay. Sometimes such barrier bars get keyed up to one end of the bay when they are called spits (Figure 7.15). Spits may also

Figure 7.15 : A satellite picture of a part of Godavari river delta showing a spit

WINDS Wind is one of the two dominant agents in hot deserts. The desert floors get heated up too much and too quickly because of being dry and barren. The heated floors heat up the air directly above them and result in upward movements in the hot lighter air with turbulence, and any obstructions in its path sets up eddies, whirlwinds, updrafts and downdrafts. Winds also move along the desert floors with great speed and the obstructions in their path create turbulence. Of course, there are storm winds which are very destructive. Winds cause deflation, abrasion and impact. Deflation includes lifting and removal of dust and smaller particles from the surface of rocks. In the transportation process sand and silt act as effective tools to abrade the land surface. The impact is simply sheer force of momentum which occurs when sand is blown into or against a rock surface. It is similar to sandblasting operation. The wind action creates a number of interesting erosional and depositional features in the deserts. In fact, many features of deserts owe their

72

formation to mass wasting and running water as sheet floods. Though rain is scarce in deserts, it comes down torrentially in a short period of time. The desert rocks devoid of vegetation, exposed to mechanical and chemical weathering processes due to drastic diurnal temperature changes, decay faster and the torrential rains help in removing the weathered materials easily. That means, the weathered debris in deserts is moved by not only wind but also by rain/sheet wash. The wind moves fine materials and general mass erosion is accomplished mainly through sheet floods or sheet wash. Stream channels in desert areas are broad, smooth and indefinite and flow for a brief time after rains.

EROSIONAL LANDFORMS Pediments and Pediplains Landscape evolution in deserts is primarily concerned with the formation and extension of pediments. Gently inclined rocky floors close to the mountains at their foot with or without a thin cover of debris, are called pediments. Such rocky floors form through the erosion of mountain front through a combination of lateral erosion by streams and sheet flooding. Erosion starts along the steep margins of the landmass or the steep sides of the tectonically controlled steep incision features over the landmass. Once, pediments are formed with a steep wash slope followed by cliff or free face above it, the steep wash slope and free face retreat backwards. This method of erosion is termed as parallel retreat of slopes through backwasting. So, through parallel retreat of slopes, the pediments extend backwards at the expense of mountain front, and gradually, the mountain gets reduced leaving an inselberg which is a remnant of the mountain. That’s how the high relief in desert areas is reduced to low featureless plains called pediplains. Playas Plains are by far the most prominent landforms in the deserts. In basins with mountains and hills around and along, the drainage is towards the centre of the basin and due to gradual

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

deposition of sediment from basin margins, a nearly level plain forms at the centre of the basin. In times of sufficient water, this plain is covered up by a shallow water body. Such types of shallow lakes are called as playas where water is retained only for short duration due to evaporation and quite often the playas contain good deposition of salts. The playa plain covered up by salts is called alkali flats. Deflation Hollows and Caves Weathered mantle from over the rocks or bare soil, gets blown out by persistent movement of wind currents in one direction. This process may create shallow depressions called deflation hollows. Deflation also creates numerous small pits or cavities over rock surfaces. The rock faces suffer impact and abrasion of wind-borne sand and first shallow depressions called blow outs are created, and some of the blow outs become deeper and wider fit to be called caves. Mushroom, Table and Pedestal Rocks Many rock-outcrops in the deserts easily susceptible to wind deflation and abrasion are worn out quickly leaving some remnants of resistant rocks polished beautifully in the shape of mushroom with a slender stalk and a broad and rounded pear shaped cap above. Sometimes, the top surface is broad like a table top and quite often, the remnants stand out like pedestals. List the erosional features carved out by wind action and action of sheet floods.

Depositional Landforms Wind is a good sorting agent. Depending upon the velocity of wind, different sizes of grains are moved along the floors by rolling or saltation and carried in suspension and in this process of transportation itself, the materials get sorted. When the wind slows or begins to die down, depending upon sizes of grains and their critical velocities, the grains will begin to settle. So, in depositional landforms made by wind, good sorting of grains can be found. Since

LANDFORMS AND THEIR EVOLUTION

73

wind is there everywhere and wherever there is good source of sand and with constant wind directions, depositional features in arid regions can develop anywhere. Sand Dunes Dry hot deserts are good places for sand dune formation. Obstacles to initiate dune formation

Figure 7.16 : Various types of sand dunes Arrows indicate wind direction

are equally important. There can be a great variety of dune forms (Figure 7.16). Barchans Crescent shaped dunes called barchans with the points or wings directed away from wind direction i.e., downwind, form where the wind direction is constant and moderate and where the original surface over which sand is moving is almost uniform. Parabolic dunes form when sandy surfaces are partially covered with vegetation. That means parabolic dunes are reversed barchans with wind direction being the same. Seif is similar to barchan with a small difference. Seif has only one wing or point. This happens when there is shift in wind conditions. The lone wings of seifs can grow very long and high. Longitudinal dunes form when supply of sand is poor and wind direction is constant. They appear as long ridges of considerable length but low in height. Transverse dunes are aligned perpendicular to wind direction. These dunes form when the wind direction is constant and the source of sand is an elongated feature at right angles to the wind direction. They may be very long and low in height. When sand is plenty, quite often, the regular shaped dunes coalesce and lose their individual characteristics. Most of the dunes in the deserts shift and a few of them will get stabilised especially near human habitations.

EXERCISES 1.

Multiple choice questions. (i) In which of the following stages of landform development, downward cutting is dominated? (a) Youth stage

(c) Early mature stage

(b) Late mature stage

(d) Old stage

(ii) A deep valley characterised by steep step-like side slopes is known as (a) U-shaped valley

(c) Blind valley

(b) Gorge

(d) Canyon

(iii) In which one of the following regions the chemical weathering process is more dominant than the mechanical process? (a) Humid region (b) Limestone region

(c) Arid region (d) Glacier region

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

74

(iv)

(v)

2.

(a)

A small to medium sized shallow depression

(b)

A landform whose opening is more or less circular at the top and funnel shaped towards bottom

(c)

A landform forms due to dripping water from surface

(d)

An irregular surface with sharp pinnacles, grooves and ridges

A deep, long and wide trough or basin with very steep concave high walls at its head as well as in sides is known as: (a) Cirque

(c) Lateral Moraine

(b) Glacial valley

(d) Esker

Answer the following questions in about 30 words. (i) (ii)

What do incised meanders in rocks and meanders in plains of alluvium indicate? Explain the evolution of valley sinks or uvalas.

(iii)

Underground flow of water is more common than surface run-off in limestone areas. Why?

(iv)

Glacial valleys show up many linear depositional forms. locations and names.

(v) 3.

Which one of the following sentences best defines the term ‘Lapies’ ?

Give their

How does wind perform its task in desert areas? Is it the only agent responsible for the erosional features in the deserts?

Answer the following questions in about 150 words. (i)

Running water is by far the most dominating geomorphic agent in shaping the earth’s surface in humid as well as in arid climates. Explain.

(ii)

Limestones behave differently in humid and arid climates. Why? What is the dominant and almost exclusive geomorphic process in limestone areas and what are its results?

(iii)

How do glaciers accomplish the work of reducing high mountains into low hills and plains?

Project Work Identify the landforms, materials and processes around your area.

UNIT IV CLIMATE This unit deals with •

Atmosphere — compositions and structure; elements of weather and climate

•

Insolation — angle of incidence and distribution; heat budget of the earth — heating and cooling of atmosphere (conduction, convection, terrestrial radiation, advection); temperature — factors controlling temperature; distribution of temperature — horizontal and vertical; inversion of temperature

•

Pressure — pressure belts; winds-planetary seasonal and local, air masses and fronts; tropical and extra tropical cyclones

•

Precipitation — evaporation; condensation — dew, frost, fog, mist and cloud; rainfall — types and world distributon

•

World climates — classification (Koeppen), greenhouse effect, global warming and climatic changes

CHAPTER

COMPOSITION

OF

C

an a person live without air? We eat food two - three times a day and drink water more frequently but breathe every few seconds. Air is essential to the survival of all organisms. Some organisms like humans may survive for some time without food and water but can’t survive even a few minutes without breathing air. That shows the reason why we should understand the atmosphere in greater detail. Atmosphere is a mixture of different gases and it envelopes the earth all round. It contains life-giving gases like oxygen for humans and animals and carbon dioxide for plants. The air is an integral part of the earth’s mass and 99 per cent of the total mass of the atmosphere is confined to the height of 32 km from the earth’s surface. The air is colourless and odourless and can be felt only when it blows as wind. Can you imagine what will happen to us in the absence of ozone in the atmosphere?

COMPOSITION

OF THE

ATMOSPHERE

The atmosphere is composed of gases, water vapour and dust particles. Table 8.1 shows details of various gases in the air, particularly in the lower atmosphere. The proportion of gases changes in the higher layers of the atmosphere in such a way that oxygen will be almost in negligible quantity at the height of 120 km. Similarly, carbon dioxide and water vapour are found only up to 90 km from the surface of the earth.

STRUCTURE ATMOSPHERE

AND

Table 8.1 : Permanent Gases of the Atmosphere Constituent Nitrogen Oxygen Argon Carbon dioxide Neon Helium Krypto Xenon Hydrogen

Formula N2 O2 Ar CO2 Ne He Kr Xe H2

Percentage by Volume 78.08 20.95 0.93 0.036 0.002 0.0005 0.001 0.00009 0.00005

Gases Carbon dioxide is meteorologically a very important gas as it is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation. It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface. It is largely responsible for the green house effect. The volume of other gases is constant but the volume of carbon dioxide has been rising in the past few decades mainly because of the burning of fossil fuels. This has also increased the temperature of the air. Ozone is another important component of the atmosphere found between 10 and 50 km above the earth’s surface and acts as a filter and absorbs the ultra-violet rays radiating from the sun and prevents them from reaching the surface of the earth. Water Vapour Water vapour is also a variable gas in the atmosphere, which decreases with altitude. In the warm and wet tropics, it may account for

77

COMPOSITION AND STRUCTURE OF ATMOSPHERE

four per cent of the air by volume, while in the dry and cold areas of desert and polar regions, it may be less than one per cent of the air. Water vapour also decreases from the equator towards the poles. It also absorbs parts of the insolation from the sun and preserves the earth’s radiated heat. It thus, acts like a blanket allowing the earth neither to become too cold nor too hot. Water vapour also contributes to the stability and instability in the air. Dust Particles Atmosphere has a sufficient capacity to keep small solid particles, which may originate from different sources and include sea salts, fine soil, smoke-soot, ash, pollen, dust and disintegrated particles of meteors. Dust particles are generally concentrated in the lower layers of the atmosphere; yet, convectional air currents may transport them to great heights. The higher concentration of dust particles is found in subtropical and temperate regions due to dry winds in comparison to equatorial and polar regions. Dust and salt particles act as hygroscopic nuclei around which water vapour condenses to produce clouds.

STRUCTURE

OF THE

The zone separating the tropsophere from stratosphere is known as the tropopause. The air temperature at the tropopause is about minus 800C over the equator and about minus 45oC over the poles. The temperature here is nearly constant, and hence, it is called the tropopause. The stratosphere is found above the tropopause and extends up to a height of 50 km. One important feature of the stratosphere is that it contains the ozone layer. This layer absorbs ultra-violet radiation and shields life on the earth from intense, harmful form of energy. The mesosphere lies above the stratosphere, which extends up to a height of 80 km. In this layer, once again, temperature starts decreasing with the increase in altitude and reaches up to minus 100°C at the height of 80 km. The upper limit of mesosphere is known as the mesopause. The ionosphere is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence, it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by this layer. Temperature here starts increasing with height. The uppermost layer of the atmosphere above

ATMOSPHERE

The atmosphere consists of different layers with varying density and temperature. Density is highest near the surface of the earth and decreases with increasing altitude. The column of atmosphere is divided into five different layers depending upon the temperature condition. They are: troposphere, stratosphere, mesosphere, ionosphere and exosphere. The troposphere is the lowermost layer of the atmosphere. Its average height is 13 km and extends roughly to a height of 8 km near the poles and about 18 km at the equator. Thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents. This layer contains dust particles and water vapour. All changes in climate and weather take place in this layer. The temperature in this layer decreases at the rate of 1°C for every 165m of height. This is the most important layer for all biological activity.

Figure 8.1 : Structure of atmosphere

78

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

the ionosphere is known as the exosphere. This is the highest layer but very little is known about it. Whatever contents are there, these are extremely rarefied in this layer, and it gradually merges with the outer space. Although all layers of the atmosphere must be exercising influence on us, geographers are concerned with the first two layers of the atmosphere.

Elements of Weather and Climate The main elements of atmosphere which are subject to change and which influence human life on earth are temperature, pressure, winds, humidity, clouds and precipitation. These elements have been dealt in detail in Chapters 9, 10 and 11.

EXERCISES 1.

Multiple choice questions. (i) Which one of the following gases constitutes the major portion of the atmosphere? (a) Oxygen

(c) Argon

(b) Nitrogen

(d) Carbon dioxide

(ii) Atmospheric layer important for human beings is: (a) Stratosphere

(c) Troposphere

(b) Mesosphere

(d) Ionosphere

(iii) Sea salt, pollen, ash, smoke soot, fine soil — these are associated with:

(iv)

(v)

2.

(c) Water vapour

(b) Dust particles

(d) Meteors

Oxygen gas is in negligible quantity at the height of atmosphere: (a) 90 km

(c) 100 km

(b) 120 km

(d) 150 km

Which one of the following gases is transparent to incoming solar radiation and opaque to outgoing terrestrial radiation? (a) Oxygen

(c) Helium

(b) Nitrogen

(d) Carbon dioxide

Answer the following questions in about 30 words. (i) (ii)

3.

(a) Gases

What do you understand by atmosphere? What are the elements of weather and climate?

(iii)

Describe the composition of atmosphere.

(iv)

Why is troposphere the most important of all the layers of the atmosphere?

Answer the following questions in about 150 words. (i) (ii)

Describe the composition of the atmosphere. Draw a suitable diagram for the structure of the atmosphere and label it and describe it.

CHAPTER

SOLAR RADIATION, HEAT BALANCE AND TEMPERATURE

D

o you feel air around you? Do you know that we live at the bottom of a huge pile of air? We inhale and exhale but we feel the air when it is in motion. It means air in motion is wind. You have already learnt about the fact that earth is surrounded by air all around. This envelop of air is atmosphere which is composed of numerous gases. These gases support life over the earth’s surface. The earth receives almost all of its energy from the sun. The earth in turn radiates back to space the energy received from the sun. As a result, the earth neither warms up nor does it get cooled over a period of time. Thus, the amount of heat received by different parts of the earth is not the same. This variation causes pressure differences in the atmosphere. This leads to transfer of heat from one region to the other by winds. This chapter explains the process of heating and cooling of the atmosphere and the resultant temperature distribution over the earth’s surface.

SOLAR RADIATION The earth’s surface receives most of its energy in short wavelengths. The energy received by the earth is known as incoming solar radiation which in short is termed as insolation. As the earth is a geoid resembling a sphere, the sun’s rays fall obliquely at the top of the atmosphere and the earth intercepts a very small portion of the sun’s energy. On an average the earth receives 1.94 calories per sq. cm per minute at the top of its atmosphere.

The solar output received at the top of the atmosphere varies slightly in a year due to the variations in the distance between the earth and the sun. During its revolution around the sun, the earth is farthest from the sun (152 million km on 4th July). This position of the earth is called aphelion. On 3rd January, the earth is the nearest to the sun (147 million km). This position is called perihelion. Therefore, the annual insolation received by the earth on 3rd January is slightly more than the amount received on 4th July. However, the effect of this variation in the solar output is masked by other factors like the distribution of land and sea and the atmospheric circulation. Hence, this variation in the solar output does not have great effect on daily weather changes on the surface of the earth. Variability of Insolation at the Surface of the Earth The amount and the intensity of insolation vary during a day, in a season and in a year. The factors that cause these variations in insolation are : (i) the rotation of earth on its axis; (ii) the angle of inclination of the sun’s rays; (iii) the length of the day; (iv) the transparency of the atmosphere; (v) the configuration of land in terms of its aspect. The last two however, have less influence. The fact that the earth’s axis makes an angle of 66½ with the plane of its orbit round the sun has a greater influence on the amount of insolation received at different latitudes. Note the variations in the duration of the day at different latitudes on solstices given in Table 9.1.

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

The second factor that determines the amount of insolation received is the angle of

colour of the sky are the result of scattering of light within the atmosphere.

Table 9.1 : Length of the Day in Hours and Minutes on Winter and Summer Solstices in the Northern Hemisphere Latitude

0°

20°

40°

60°

90°

December 22

12h 00m

10h 48m

9h 8m

5h 33m

0

June 21

12 h

13h 12m

14h 52m

18h 27m

6 months

inclination of the rays. This depends on the latitude of a place. The higher the latitude the less is the angle they make with the surface of the earth resulting in slant sun rays. The area covered by vertical rays is always less than the slant rays. If more area is covered, the energy gets distributed and the net energy received per unit area decreases. Moreover, the slant rays are required to pass through greater depth of the atmosphere resulting in more absorption, scattering and diffusion.

Spatial Distribution of Insolation at the Earth’s Surface The insolation received at the surface varies from about 320 Watt/m2 in the tropics to about 70 Watt/m2 in the poles. Maximum insolation is received over the subtropical deserts, where the cloudiness is the least. Equator receives comparatively less insolation than the tropics. Generally, at the same latitude the insolation is more over the continent than over the oceans. In winter, the middle and higher latitudes receive less radiation than in summer.

HEATING

Figure 9.1 : Summer Solstice

The Passage of Solar Radiation through the Atmosphere The atmosphere is largely transparent to short wave solar radiation. The incoming solar radiation passes through the atmosphere before striking the earth’s surface. Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation. Very small-suspended particles in the troposphere scatter visible spectrum both to the space and towards the earth surface. This process adds colour to the sky. The red colour of the rising and the setting sun and the blue

AND

COOLING

OF

ATMOSPHERE

There are different ways of heating and cooling of the atmosphere. The earth after being heated by insolation transmits the heat to the atmospheric layers near to the earth in long wave form. The air in contact with the land gets heated slowly and the upper layers in contact with the lower layers also get heated. This process is called conduction. Conduction takes place when two bodies of unequal temperature are in contact with one another, there is a flow of energy from the warmer to cooler body. The transfer of heat continues until both the bodies attain the same temperature or the contact is broken. Conduction is important in heating the lower layers of the atmosphere. The air in contact with the earth rises vertically on heating in the form of currents and further transmits the heat of the atmsphere. This process of vertical heating of the atmosphere is known as convection. The convective transfer of energy is confined only to the troposphere. The transfer of heat through horizontal movement of air is called advection. Horizontal movement of the air is relatively more important

81

SOLAR RADIATION, HEAT BALANCE AND TEMPERATURE

than the vertical movement. In middle latitudes, most of dirunal (day and night) variation in daily weather are caused by advection alone. In tropical regions particularly in northern India during summer season local winds called ‘loo’ is the outcome of advection process. Terrestrial Radiation The insolation received by the earth is in short waves forms and heats up its surface. The earth after being heated itself becomes a radiating body and it radiates energy to the atmosphere in long wave form. This energy heats up the atmosphere from below. This process is known as terrestrial radiation. The long wave radiation is absorbed by the atmospheric gases particularly by carbon dioxide and the other green house gases. Thus, the atmosphere is indirectly heated by the earth’s radiation. The atmosphere in turn radiates and transmits heat to the space. Finally the amount of heat received from the sun is returned to space, thereby maintaining constant temperature at the earth’s surface and in the atmosphere. Heat Budget of the Planet Earth Figure 9.2 depicts the heat budget of the planet earth. The earth as a whole does not

accumulate or loose heat. It maintains its temperature. This can happen only if the amount of heat received in the form of insolation equals the amount lost by the earth through terrestrial radiation. Consider that the insolation received at the top of the atmosphere is 100 per cent. While passing through the atmosphere some amount of energy is reflected, scattered and absorbed. Only the remaining part reaches the earth surface. Roughly 35 units are reflected back to space even before reaching the earth’s surface. Of these, 27 units are reflected back from the top of the clouds and 2 units from the snow and ice-covered areas of the earth. The reflected amount of radiation is called the albedo of the earth. The remaining 65 units are absorbed, 14 units within the atmosphere and 51 units by the earth’s surface. The earth radiates back 51 units in the form of terrestrial radiation. Of these, 17 units are radiated to space directly and the remaining 34 units are absorbed by the atmosphere (6 units absorbed directly by the atmosphere, 9 units through convection and turbulence and 19 units through latent heat of condensation). 48 units absorbed by the atmosphere (14 units from insolation +34 units from

Figure 9.2 : Heat budget of the earth

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

terrestrial radiation) are also radiated back into space. Thus, the total radiation returning from the earth and the atmosphere respectively is 17+48=65 units which balance the total of 65 units received from the sun. This is termed the heat budget or heat balance of the earth. This explains, why the earth neither warms up nor cools down despite the huge transfer of heat that takes place. Variation in the Net Heat Budget at the Earth’s Surface As explained earlier, there are variations in the amount of radiation received at the earth’s surface. Some part of the earth has surplus radiation balance while the other part has deficit. Figure 9.3 depicts the latitudinal variation in the net radiation balance of the earth — the atmosphere system. The figure shows that there is a surplus of net radiation balance between 40 degrees north and south and the regions near the poles have a deficit. The surplus heat energy from the tropics is redistributed pole wards and as a result the tropics do not get progressively heated up due to the accumulation of excess heat or the high latitudes get permanently frozen due to excess deficit.

Figure 9.3 : Latitudinal variation in net radiation balance

Temperature The interaction of insolation with the atmosphere and the earth’s surface creates

heat which is measured in terms of temperature. While heat represents the molecular movement of particles comprising a substance, the temperature is the measurement in degrees of how hot (or cold) a thing (or a place) is. Factors Controlling Temperature Distribution The temperature of air at any place is influenced by (i) the latitude of the place; (ii) the altitude of the place; (iii) distance from the sea, the airmass circulation; (iv) the presence of warm and cold ocean currents; (v) local aspects. The latitude : The temperature of a place depends on the insolation received. It has been explained earlier that the insolation varies according to the latitude hence the temperature also varies accordingly. The altitude : The atmosphere is indirectly heated by terrestrial radiation from below. Therefore, the places near the sea-level record higher temperature than the places situated at higher elevations. In other words, the temperature generally decreases with increasing height. The rate of decrease of temperature with height is termed as the normal lapse rate. It is 6.5°C per 1,000 m. Distance from the sea : Another factor that influences the temperature is the location of a place with respect to the sea. Compared to land, the sea gets heated slowly and loses heat slowly. Land heats up and cools down quickly. Therefore, the variation in temperature over the sea is less compared to land. The places situated near the sea come under the moderating influence of the sea and land breezes which moderate the temperature. Air-mass and Ocean currents : Like the land and sea breezes, the passage of air masses also affects the temperature. The places, which come under the influence of warm air-masses experience higher temperature and the places that come under the influence of cold airmasses experience low temperature. Similarly,

83

SOLAR RADIATION, HEAT BALANCE AND TEMPERATURE

the places located on the coast where the warm ocean currents flow record higher temperature than the places located on the coast where the cold currents flow. Distribution of Temperature The global distribution of temperature can well be understood by studying the temperature distribution in January and July. The temperature distribution is generally shown on the map with the help of isotherms. The Isotherms are lines joining places having equal temperature. Figure 9.4 (a) and (b) show the distribution of surface air temperature in the month of January and July. In general the effect of the latitude on temperature is well pronounced on the map, as the isotherms are generally parallel to the latitude. The deviation from this general trend is more pronounced in January than in July, especially in the northern hemisphere. In the

northern hemisphere the land surface area is much larger than in the southern hemisphere. Hence, the effects of land mass and the ocean currents are well pronounced. In January the isotherms deviate to the north over the ocean and to the south over the continent. This can be seen on the North Atlantic Ocean. The presence of warm ocean currents, Gulf Stream and North Atlantic drift, make the Northern Atlantic Ocean warmer and the isotherms bend towards the north. Over the land the temperature decreases sharply and the isotherms bend towards south in Europe. It is much pronounced in the Siberian plain. The mean January temperature along 60° E longitude is minus 20° C both at 80° N and 50° N latitudes. The mean monthly temperature for January is over 27° C, in equatorial oceans over 24° C in the tropics and 2° C - 0° C in the middle latitudes and –18° C to –48° C in the Eurasian continental interior.

Figure 9.4 (a) : The distribution of surface air temperature in the month of January

84

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Figure 9.4 (b) : The distribution of surface air temperature in the month of July

Figure 9.5 : The range of temperature between January and July

85

SOLAR RADIATION, HEAT BALANCE AND TEMPERATURE

The effect of the ocean is well pronounced in the southern hemisphere. Here the isotherms are more or less parallel to the latitudes and the variation in temperature is more gradual than in the northern hemisphere. The isotherm of 20° C, 10° C, and 0° C runs parallel to 35° S, 45° S and 60° S latitudes respectively. In July the isotherms generally run parallel to the latitude. The equatorial oceans record warmer temperature, more than 27°C. Over the land more than 30°C is noticed in

the subtropical continental region of Asia, along the 30° N latitude. Along the 40° N runs the isotherm of 10° C and along the 40° S the temperature is 10° C. Figure 9.5 shows the range of temperature between January and July. The highest range of temperature is more than 60° C over the north-eastern part of Eurasian continent. This is due to continentality. The least range of temperature, 3°C, is found between 20° S and 15° N.

EXERCISES 1.

Multiple choice questions. (i) The sun is directly overhead at noon on 21st June at: (a) The equator

(c) 23.5° N

(b) 23.5° S

(d) 66.5° N

(ii) In which one of the following cities, are the days the longest? (a) Tiruvanantpuram

(c) Hyderabad

(b) Chandigarh

(d) Nagpur

(iii) The atmosphere is mainly heated by the: (a) Short wave solar radiation (c) Long wave terrestrial radiation (b) Reflected solar radiation (iv)

Make correct pairs from the following two columns. (i) Insolation

(v)

(d) Scattered solar radiation

(a) The difference between the mean temperature of the warmest and the coldest months

(ii) Albedo

(b) The lines joining the places of equal temperature

(iii) Isotherm

(c)

(iv) Annual range

(d) The percentage of visible light reflected by an object

The incoming solar radiation

The main reason that the earth experiences highest temperatures in the subtropics in the northern hemisphere rather than at the equator is : (a)

Subtropical areas tend to have less cloud cover than equatorial areas.

(b)

Subtropical areas have longer day hours in the summer than the equatorial.

(c)

Subtropical areas have an enhanced “green house effect” compared to equatorial areas.

(d)

Subtropical areas are nearer to the oceanic areas than the equatorial locations.

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

2.

3.

Answer the following questions in about 30 words. (i)

How does the unequal distribution of heat over the planet earth in space and time cause variations in weather and climate?

(ii)

What are the factors that control temperature distribution on the surface of the earth?

(iii)

In India, why is the day temperature maximum in May and why not after the summer solstice?

(iv)

Why is the annual range of temperature high in the Siberian plains?

Answer the following questions in about 150 words. (i)

How do the latitude and the tilt in the axis of rotation of the earth affect the amount of radiation received at the earth’s surface?

(ii)

Discuss the processes through which the earth-atmosphere system maintains heat balance.

(iii)

Compare the global distribution of temperature in January over the northern and the southern hemisphere of the earth.

Project Work Select a meteorological observatory located in your city or near your town. Tabulate the temperature data as given in the climatological table of observatories : (i) (ii)

Note the altitude, latitude of the observatory and the period for which the mean is calculated. Define the terms related to temperature as given in the table.

(iii)

Calculate the daily mean monthly temperature.

(iv)

Draw a graph to show the daily mean maximum, the daily mean minimum and the mean temperature.

(v)

Calculate the annual range of temperature.

(vi)

Find out in which months the daily range of temperature is the highest and the lowest.

(vii)

List out the factors that determine the temperature of the place and explain the possible causes for temperature variation in the months of January, May, July and October. Example Observatory

:

New Delhi (Safdarjung)

Latitude

:

28°35°’ N

Based on observations

:

1951 - 1980

Altitude above mean sea level

:

216 m

Month

Mean of Daily Max.(°C)

Mean of Daily Min.(°C)

Highest Recorded (°C)

Lowest Recorded (°C)

January

21.1

7.3

29.3

0.6

May

39.6

25.9

47.2

17.5

SOLAR RADIATION, HEAT BALANCE AND TEMPERATURE

Daily mean monthly temperature January

May

21.1+7.3 = 14.2OC 2

39.6+25.9 = 32.75OC 2

Annual range of temperature Mean Max. Temperature in May - Mean Temperature in January Annual range of temperature = 32.75°C – 14.2°C = 18.55°C

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CHAPTER

ATMOSPHERIC CIRCULATION AND WEATHER SYSTEMS

E

arlier Chapter 9 described the uneven distribution of temperature over the surface of the earth. Air expands when heated and gets compressed when cooled. This results in variations in the atmospheric pressure. The result is that it causes the movement of air from high pressure to low pressure, setting the air in motion. You already know that air in horizontal motion is wind. Atmospheric pressure also determines when the air will rise or sink. The wind redistributes the heat and moisture across the planet, thereby, maintaining a constant temperature for the planet as a whole. The vertical rising of moist air cools it down to form the clouds and bring precipitation. This chapter has been devoted to explain the causes of pressure differences, the forces that control the atmospheric circulation, the turbulent pattern of wind, the formation of air masses, the disturbed weather when air masses interact with each other and the phenomenon of violent tropical storms.

ATMOSPHERIC PRESSURE Do you realise that our body is subjected to a lot of air pressure. As one moves up the air gets varified and one feels breathless. The weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere is called the atmospheric pressure. The atmospheric pressure is expressed in units of mb and Pascals. The widely used unit is kilo Pascal written as hPa. At sea level the average atmospheric pressure is 1,013.2 mb or 1,013.2 hPa. Due to gravity

the air at the surface is denser and hence has higher pressure. Air pressure is measured with the help of a mercury barometer or the aneroid barometer. Consult your book, Practical Work in Geography — Part I (NCERT, 2006) and learn about these instruments. The pressure decreases with height. At any elevation it varies from place to place and its variation is the primary cause of air motion, i.e. wind which moves from high pressure areas to low pressure areas. Vertical Variation of Pressure In the lower atmosphere the pressure decreases rapidly with height. The decrease amounts to about 1 mb for each 10 m increase in elevation. It does not always decrease at the same rate. Table 10.1 gives the average pressure and temperature at selected levels of elevation for a standard atmosphere. Table 10.1 : Standard Pressure and Temperature at Selected Levels Level Sea Level

Pressure in mb

Temperature °C

1,013.25

15.2

1 km

898.76

8.7

5 km

540.48

–17. 3

10 km

265.00

– 49.7

The vertical pressure gradient force is much larger than that of the horizontal pressure gradient. But, it is generally balanced by a nearly equal but opposite gravitational force. Hence, we do not experience strong upward winds.

89

ATMOSPHERIC CIRCULATION AND WEATHER SYSTEMS

Horizontal Distribution of Pressure Small differences in pressure are highly significant in terms of the wind direction and

purposes of comparison. The sea level pressure distribution is shown on weather maps. Figure 10.1 shows the patterns of isobars corresponding to pressure systems. Lowpressure system is enclosed by one or more isobars with the lowest pressure in the centre. High-pressure system is also enclosed by one or more isobars with the highest pressure in the centre. World Distribution of Sea Level Pressure

Figure 10.1 : Isobars, pressure and wind systems in Northern Hemisphere

velocity. Horizontal distribution of pressure is studied by drawing isobars at constant levels. Isobars are lines connecting places having equal pressure. In order to eliminate the effect of altitude on pressure, it is measured at any station after being reduced to sea level for

The world distribution of sea level pressure in January and July has been shown in Figures 10.2 and 10.3. Near the equator the sea level pressure is low and the area is known as equatorial low. Along 30° N and 30o S are found the high-pressure areas known as the subtropical highs. Further pole wards along 60o N and 60o S, the low-pressure belts are termed as the sub polar lows. Near the poles the pressure is high and it is known as the polar high. These pressure belts are not permanent

Figure 10.2 : Distribution of pressure (in millibars) — January

90

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Figure 10.3 : Distribution of pressure (in millibars) — July

in nature. They oscillate with the apparent movement of the sun. In the northern hemisphere in winter they move southwards and in the summer northwards. Forces Affecting the Velocity and Direction of Wind You already know that the air is set in motion due to the differences in atmospheric pressure. The air in motion is called wind. The wind blows from high pressure to low pressure. The wind at the surface experiences friction. In addition, rotation of the earth also affects the wind movement. The force exerted by the rotation of the earth is known as the Coriolis force. Thus, the horizontal winds near the earth surface respond to the combined effect of three forces – the pressure gradient force, the frictional force and the Coriolis force. In addition, the gravitational force acts downward.

Pressure Gradient Force The differences in atmospheric pressure produces a force. The rate of change of pressure with respect to distance is the pressure gradient. The pressure gradient is strong where the isobars are close to each other and is weak where the isobars are apart. Frictional Force It affects the speed of the wind. It is greatest at the surface and its influence generally extends upto an elevation of 1 - 3 km. Over the sea surface the friction is minimal. Coriolis Force The rotation of the earth about its axis affects the direction of the wind. This force is called the Coriolis force after the French physicist who described it in 1844. It deflects the wind to the right direction in the northern hemisphere and

91

ATMOSPHERIC CIRCULATION AND WEATHER SYSTEMS

to the left in the southern hemisphere. The deflection is more when the wind velocity is high. The Coriolis force is directly proportional to the angle of latitude. It is maximum at the poles and is absent at the equator. The Coriolis force acts perpendicular to the pressure gradient force. The pressure gradient force is perpendicular to an isobar. The higher the pressure gradient force, the more is the velocity of the wind and the larger is the deflection in the direction of wind. As a result of these two forces operating perpendicular to each other, in the low-pressure areas the wind blows around it. At the equator, the Coriolis force is zero and the wind blows perpendicular to the isobars. The low pressure gets filled instead of getting intensified. That is the reason why tropical cyclones are not formed near the equator.

The wind circulation around a low is called cyclonic circulation. Around a high it is called anti cyclonic circulation. The direction of winds around such systems changes according to their location in different hemispheres (Table 10.2). The wind circulation at the earth’s surface around low and high on many occasions is closely related to the wind circulation at higher level. Generally, over low pressure area the air will converge and rise. Over high pressure area the air will subside from above and diverge at the surface (Figure10.5). Apart from convergence, some eddies, convection currents, orographic uplift and uplift along fronts cause the rising of air, which is essential for the formation of clouds and precipitation.

Pressure and Wind The velocity and direction of the wind are the net result of the wind generating forces. The winds in the upper atmosphere, 2 - 3 km above the surface, are free from frictional effect of the surface and are controlled by the pressure gradient and the Coriolis force. When isobars are straight and when there is no friction, the pressure gradient force is balanced by the Coriolis force and the resultant wind blows parallel to the isobar. This wind is known as the geostrophic wind (Figure 10.4).

Figure 10.4 : Geostropic Wind

Figure 10.5 : Convergence and divergence of winds

General circulation of the atmosphere The pattern of planetary winds largely depends on : (i) latitudinal variation of atmospheric heating; (ii) emergence of pressure belts; (iii) the migration of belts following apparent path of the sun; (iv) the distribution of continents and oceans; (v) the rotation of earth. The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth’s

Table 10.2 : Pattern of Wind Direction in Cyclones and Anticyclones Pressure System

Pressure Condition at the Centre

Pattern of Wind Direction Northern Hemisphere Southern Hemisphere

Cyclone

Low

Anticlockwise

Clockwise

Anticyclone

High

Clockwise

Anticlockwise

92

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

climate. A schematic description of the general circulation is shown in Figure 10.6.

The general circulation of the atmosphere also affects the oceans. The large-scale winds of the atmosphere initiate large and slow moving currents of the ocean. Oceans in turn provide input of energy and water vapour into the air. These interactions take place rather slowly over a large part of the ocean. General Atmospheric Circulation and its Effects on Oceans

Figure 10. 6 : Simplified general circulation of the atmosphere

The air at the Inter Tropical Convergence Zone (ITCZ) rises because of convection caused by high insolation and a low pressure is created. The winds from the tropics converge at this low pressure zone. The converged air rises along with the convective cell. It reaches the top of the troposphere up to an altitude of 14 km. and moves towards the poles. This causes accumulation of air at about 30o N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30o N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies. The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ). Such circulations from the surface upwards and vice-versa are called cells. Such a cell in the tropics is called Hadley Cell. In the middle latitudes the circulation is that of sinking cold air that comes from the poles and the rising warm air that blows from the subtropical high. At the surface these winds are called westerlies and the cell is known as the Ferrel cell. At polar latitudes the cold dense air subsides near the poles and blows towards middle latitudes as the polar easterlies. This cell is called the polar cell. These three cells set the pattern for the general circulation of the atmosphere. The transfer of heat energy from lower latitudes to higher latitudes maintains the general circulation.

Warming and cooling of the Pacific Ocean is most important in terms of general atmospheric circulation. The warm water of the central Pacific Ocean slowly drifts towards South American coast and replaces the cool Peruvian current. Such appearance of warm water off the coast of Peru is known as the El Nino. The El Nino event is closely associated with the pressure changes in the Central Pacific and Australia. This change in pressure condition over Pacific is known as the southern oscillation. The combined phenomenon of southern oscillation and El Nino is known as ENSO. In the years when the ENSO is strong, large-scale variations in weather occur over the world. The arid west coast of South America receives heavy rainfall, drought occurs in Australia and sometimes in India and floods in China. This phenomenon is closely monitored and is used for long range forecasting in major parts of the world.

Seasonal Wind The pattern of wind circulation is modified in different seasons due to the shifting of regions of maximum heating, pressure and wind belts. The most pronounced effect of such a shift is noticed in the monsoons, especially over southeast Asia. You would be studying the details of monsoon in the book India : Physical Environment (NCERT, 2006). The other local deviations from the general circulation system are as follows. Local Winds Differences in the heating and cooling of earth surfaces and the cycles those develop daily or annually can create several common, local or regional winds.

93

ATMOSPHERIC CIRCULATION AND WEATHER SYSTEMS

Land and Sea Breezes As explained earlier, the land and sea absorb and transfer heat differently. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results (Figure 10.7).

as the valley breeze. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind. Another type of warm wind occurs on the leeward side of the mountain ranges. The moisture in these winds, while crossing the mountain ranges condense and precipitate. When it descends down the leeward side of the slope the dry air gets warmed up by adiabatic process. This dry air may melt the snow in a short time. Air Masses When the air remains over a homogenous area for a sufficiently longer time, it acquires the characteristics of the area. The homogenous regions can be the vast ocean surface or vast plains. The air with distinctive characteristics in terms of temperature and humidity is called an airmass. It is defined as a large body of air having little horizontal variation in temperature and moisture. The homogenous surfaces, over which air masses form, are called the source regions. The air masses are classified according to the source regions. There are five major source regions. These are: (i) Warm tropical and subtropical oceans; (ii) The subtropical hot deserts; (iii) The relatively cold high latitude oceans; (iv) The very cold snow covered continents in high latitudes; (v) Permanently ice covered continents in the Arctic and Antarctica. Accordingly, following types of airmasses are recognised: (i) Maritime tropical (mT); (ii) Continental tropical (cT); (iii) Maritime polar (mP); (iv) Continental polar (cP); (v) Continental arctic (cA). Tropical air masses are warm and polar air masses are cold. Fronts

Figure 10.7 : Land and sea breezes

Mountain and Valley Winds In mountainous regions, during the day the slopes get heated up and air moves upslope and to fill the resulting gap the air from the valley blows up the valley. This wind is known

When two different air masses meet, the boundary zone between them is called a front. The process of formation of the fronts is known as frontogenesis. There are four types of fronts: (a) Cold; (b) Warm; (c) Stationary; (d) Occluded [(Figure10.8 (a), (b), (c)]. When the front remains stationary, it is called a stationary front. When the cold air moves

94

Figure 10.8 : Vertical Sections of : (a) Warm Front; (b) Cold Front; (c) Occluded Front

towards the warm air mass, its contact zone is called the cold front, whereas if the warm air mass moves towards the cold air mass, the contact zone is a warm front. If an air mass is fully lifted above the land surface, it is called the occluded front. The fronts occur in middle latitudes and are characterised by steep gradient in temperature and pressure. They bring abrupt changes in temperature and cause the air to rise to form clouds and cause precipitation.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

anticlockwise cyclonic circulation. The cyclonic circulation leads to a well developed extra tropical cyclone, with a warm front and a cold front. The plan and cross section of a well developed cyclone is given in Figure 10.9. There are pockets of warm air or warm sector wedged between the forward and the rear cold air or cold sector. The warm air glides over the cold air and a sequence of clouds appear over the sky ahead of the warm front and cause precipitation. The cold front approaches the warm air from behind and pushes the warm air up. As a result, cumulus clouds develop along the cold front. The cold front moves faster than the warm front ultimately overtaking the warm front. The warm air is completely lifted up and the front is occluded and the cyclone dissipates. The processes of wind circulation both at the surface and aloft are closely interlinked. The extra tropical cyclone differs from the tropical cyclone in number of ways. The extra tropical cyclones have a clear frontal system

Extra Tropical Cyclones The systems developing in the mid and high latitude, beyond the tropics are called the middle latitude or extra tropical cyclones. The passage of front causes abrupt changes in the weather conditions over the area in the middle and high latitudes. Extra tropical cyclones form along the polar front. Initially, the front is stationary. In the northern hemisphere, warm air blows from the south and cold air from the north of the front. When the pressure drops along the front, the warm air moves northwards and the cold air move towards, south setting in motion an

Figure 10. 9 : Extra tropical cyclones

ATMOSPHERIC CIRCULATION AND WEATHER SYSTEMS

which is not present in the tropical cyclones. They cover a larger area and can originate over the land and sea. Whereas the tropical cyclones originate only over the seas and on reaching the land they dissipate. The extra tropical cyclone affects a much larger area as compared to the tropical cyclone. The wind velocity in a tropical cyclone is much higher and it is more destructive. The extra tropical cyclones move from west to east but tropical cyclones, move from east to west. Tropical Cyclones Tropical cyclones are violent storms that originate over oceans in tropical areas and move over to the coastal areas bringing about large scale destruction caused by violent winds, very heavy rainfall and storm surges. This is one of the most devastating natural calamities. They are known as Cyclones in the Indian Ocean, Hurricanes in the Atlantic, Typhoons in the Western Pacific and South China Sea, and Willy-willies in the Western Australia. Tropical cyclones originate and intensify over warm tropical oceans. The conditions favourable for the formation and intensification of tropical storms are: (i) Large sea surface with temperature higher than 27° C; (ii) Presence of the Coriolis force; (iii) Small variations in the vertical wind speed; (iv) A pre-existing weaklow-pressure area or low-level-cyclonic circulation; (v) Upper divergence above the sea level system. The energy that intensifies the storm, comes from the condensation process in the towering cumulonimbus clouds, surrounding the centre of the storm. With continuous supply of moisture from the sea, the storm is further strengthened. On reaching the land the moisture supply is cut off and the storm dissipates. The place where a tropical cyclone crosses the coast is called the landfall of the cyclone. The cyclones, which cross 20o N latitude generally, recurve and they are more destructive.

95

A schematic representation of the vertical structure of a mature tropical cyclonic storm is shown in Figure 10.10. A mature tropical cyclone is characterised by the strong spirally circulating wind around the centre, called the eye. The diameter of the circulating system can vary between 150 and 250 km. The eye is a region of calm with subsiding air. Around the eye is the eye wall, where there is a strong spiralling ascent of air to greater height reaching the tropopause. The wind reaches maximum velocity in this region, reaching as high as 250 km per hour. Torrential rain occurs here. From the eye wall rain bands may radiate and trains of cumulus and cumulonimbus clouds may drift into the outer region. The diameter of the storm over the Bay of Bengal, Arabian sea and Indian ocean is between 600 - 1200 km. The system moves slowly about 300 - 500 km per day. The cyclone creates storm surges and they inundate the coastal low lands. The storm peters out on the land.

Figure 10.10 : Vertical section of the tropical cyclone (after Rama Sastry)

96

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Thunderstorms and Tornadoes Other severe local storms are thunderstorms and tornadoes. They are of short duration, occurring over a small area but are violent. Thunderstor ms are caused by intense convection on moist hot days. A thunderstorm is a well-grown cumulonimbus cloud producing thunder and lightening. When the clouds extend to heights where sub-zero temperature prevails, hails are formed and they come down as hailstorm. If there is insufficient moisture, a thunderstorm can generate duststorms. A thunderstorm is characterised by intense updraft of rising warm air, which causes the clouds to grow bigger and rise to

greater height. This causes precipitation. Later, downdraft brings down to earth the cool air and the rain. From severe thunderstorms sometimes spiralling wind descends like a trunk of an elephant with great force, with very low pressure at the centre, causing massive destruction on its way. Such a phenomenon is called a tornado. Tornadoes generally occur in middle latitudes. The tornado over the sea is called water sprouts. These violent storms are the manifestation of the atmosphere’s adjustments to varying energy distribution. The potential and heat energies are converted into kinetic energy in these storms and the restless atmosphere again returns to its stable state.

EXERCISES 1.

Multiple choice questions. (i) If the surface air pressure is 1,000 mb, the air pressure at 1 km above the surface will be: (a) 700 mb

(c) 900 mb

(b) 1,100 mb

(d) 1,300 mb

(ii) The Inter Tropical Convergence Zone normally occurs: (a) near the Equator

(b) near the Tropic of Cancer

(c) near the Tropic of Capricorn

(d) near the Arctic Circle

(iii) The direction of wind around a low pressure in northern hemisphere is:

(iv)

2.

(a) clockwise

(c) anti-clock wise

(b) perpendicular to isobars

(d) parallel to isobars

Which one of the following is the source region for the formation of air masses? (a) the Equatorial forest

(c) the Siberian Plain

(b) the Himalayas

(d) the Deccan Plateau

Answer the following questions in about 30 words. (i)

What is the unit used in measuring pressure? Why is the pressure measured at station level reduced to the sea level in preparation of weather maps?

(ii)

While the pressure gradient force is from north to south, i.e. from the subtropical high pressure to the equator in the northern hemisphere, why are the winds north easterlies in the tropics.

(iii)

What are the geotrophic winds?

(iv)

Explain the land and sea breezes.

ATMOSPHERIC CIRCULATION AND WEATHER SYSTEMS

3.

Answer the following questions in about 150 words. (i)

Discuss the factors affecting the speed and direction of wind.

(ii)

Draw a simplified diagram to show the general circulation of the atmosphere over the globe. What are the possible reasons for the formation of subtropical high pressure over 30o N and S latitudes?

(iii)

Why does tropical cyclone originate over the seas? In which part of the tropical cyclone do torrential rains and high velocity winds blow and why?

Project Work (i)

Collect weather information over media such as newspaper, TV and radio for understanding the weather systems.

(ii)

Read the section on weather in any newspaper, preferably, one having a map showing a satellite picture. Mark the area of cloudiness. Attempt to infer the atmospheric circulation from the distribution of clouds. Compare the forecast given in the newspaper with the TV coverage, if you have access to TV. Estimate, how many days in a week was the forecast were accurate.

97

CHAPTER

WATER

Y

ou have already learnt that the air contains water vapour. It varies from zero to four per cent by volume of the atmosphere and plays an important role in the weather phenomena. Water is present in the atmosphere in three forms namely – gaseous, liquid and solid. The moisture in the atmosphere is derived from water bodies through evaporation and from plants through transpiration. Thus, there is a continuous exchange of water between the atmosphere, the oceans and the continents through the processes of evaporation, transpiration, condensation and precipitation. Water vapour present in the air is known as humidity. It is expressed quantitatively in different ways. The actual amount of the water vapour present in the atmosphere is known as the absolute humidity. It is the weight of water vapour per unit volume of air and is expressed in terms of grams per cubic metre. The ability of the air to hold water vapour depends entirely on its temperature. The absolute humidity differs from place to place on the surface of the earth. The percentage of moisture present in the atmosphere as compared to its full capacity at a given temperature is known as the relative humidity. With the change of air temperature, the capacity to retain moisture increases or decreases and the relative humidity is also affected. It is greater over the oceans and least over the continents. The air containing moisture to its full capacity at a given temperature is said to be saturated. It means that the air at the given temperature is incapable of holding any additional amount of moisture at that stage. The temperature at which saturation occurs in a given sample of air is known as dew point.

EVAPORATION

IN THE

AND

ATMOSPHERE

CONDENSATION

The amount of water vapour in the atmosphere is added or withdrawn due to evaporation and condensation respectively. Evaporation is a process by which water is transformed from liquid to gaseous state. Heat is the main cause for evaporation. The temperature at which the water starts evaporating is referred to as the latent heat of vapourisation. Increase in temperature increases water absorption and retention capacity of the given parcel of air. Similarly, if the moisture content is low, air has a potentiality of absorbing and retaining moisture. Movement of air replaces the saturated layer with the unsaturated layer. Hence, the greater the movement of air, the greater is the evaporation. The transformation of water vapour into water is called condensation. Condensation is caused by the loss of heat. When moist air is cooled, it may reach a level when its capacity to hold water vapour ceases. Then, the excess water vapour condenses into liquid form. If it directly condenses into solid form, it is known as sublimation. In free air, condensation results from cooling around very small particles termed as hygroscopic condensation nuclei. Particles of dust, smoke and salt from the ocean are particularly good nuclei because they absorb water. Condensation also takes place when the moist air comes in contact with some colder object and it may also take place when the temperature is close to the dew point. Condensation, therefore, depends upon the amount of cooling and the relative humidity of the air. Condensation is influenced by the volume of air, temperature, pressure and humidity. Condensation takes place: (i) when

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the temperature of the air is reduced to dew point with its volume remaining constant; (ii) when both the volume and the temperature are reduced; (iv) when moisture is added to the air through evaporation. However, the most favourable condition for condensation is the decrease in air temperature. After condensation the water vapour or the moisture in the atmosphere takes one of the following forms — dew, frost, fog and clouds. Forms of condensation can be classified on the basis of temperature and location. Condensation takes place when the dew point is lower than the freezing point as well as higher than the freezing point. Dew When the moisture is deposited in the form of water droplets on cooler surfaces of solid objects (rather than nuclei in air above the surface) such as stones, grass blades and plant leaves, it is known as dew. The ideal conditions for its formation are clear sky, calm air, high relative humidity, and cold and long nights. For the formation of dew, it is necessary that the dew point is above the freezing point.

condition when fog is mixed with smoke, is described as smog. The only difference between the mist and fog is that mist contains more moisture than the fog. In mist each nuceli contains a thicker layer of moisture. Mists are frequent over mountains as the rising warm air up the slopes meets a cold surface. Fogs are drier than mist and they are prevalent where warm currents of air come in contact with cold currents. Fogs are mini clouds in which condensation takes place around nuclei provided by the dust, smoke, and the salt particles. Clouds Cloud is a mass of minute water droplets or tiny crystals of ice formed by the condensation of the water vapour in free air at considerable elevations. As the clouds are formed at some height over the surface of the earth, they take various shapes. According to their height, expanse, density and transparency or opaqueness clouds are grouped under four types : (i) cirrus; (ii) cumulus; (iii) stratus; (iv) nimbus. Cirrus

Frost Frost forms on cold surfaces when condensation takes place below freezing point (00C), i.e. the dew point is at or below the freezing point. The excess moisture is deposited in the form of minute ice crystals instead of water droplets. The ideal conditions for the formation of white frost are the same as those for the formation of dew, except that the air temperature must be at or below the freezing point. Fog and Mist When the temperature of an air mass containing a large quantity of water vapour falls all of a sudden, condensation takes place within itself on fine dust particles. So, the fog is a cloud with its base at or very near to the ground. Because of the fog and mist, the visibility becomes poor to zero. In urban and industrial centres smoke provides plenty of nuclei which help the formation of fog and mist. Such a

Cirrus clouds are formed at high altitudes (8,000 - 12,000m). They are thin and detatched clouds having a feathery appearance. They are always white in colour. Cumulus Cumulus clouds look like cotton wool. They are generally formed at a height of 4,000 7,000 m. They exist in patches and can be seen scattered here and there. They have a flat base. Stratus As their name implies, these are layered clouds covering large portions of the sky. These clouds are generally formed either due to loss of heat or the mixing of air masses with different temperatures. Nimbus Nimbus clouds are black or dark gray. They form at middle levels or very near to the surface

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

of the earth. These are extremely dense and opaque to the rays of the sun. Sometimes, the clouds are so low that they seem to touch the ground. Nimbus clouds are shapeless masses of thick vapour.

Figure 11.1

Precipitation The process of continuous condensation in free air helps the condensed particles to grow in size. When the resistance of the air fails to hold them against the force of gravity, they fall on to the earth’s surface. So after the condensation of water vapour, the release of moisture is known as precipitation. This may take place in liquid or solid form. The precipitation in the form of water is called rainfall, when the temperature is lower than the 00C, precipitation takes place in the form of fine flakes of snow and is called snowfall. Moisture is released in the form of hexagonal crystals. These crystals form flakes of snow. Besides rain and snow, other forms of precipitation are sleet and hail, though the latter are limited in occurrence and are sporadic in both time and space. Sleet is frozen raindrops and refrozen melted snow-water. When a layer of air with the temperature above freezing point overlies a subfreezing layer near the ground, precipitation takes place in the form of sleet. Raindrops, which leave the warmer air, encounter the colder air below. As a result, they solidify and reach the ground as small pellets of ice not bigger than the raindrops from which they are formed. Sometimes, drops of rain after being released by the clouds become solidified into small rounded solid pieces of ice and which reach the surface of the earth are called hailstones. These are formed by the rainwater passing through the colder layers. Hailstones have several concentric layers of ice one over the other. Types of Rainfall

Figure 11.2

Identify these cloud types which are shown in Figure 11.1 and 11.2.

On the basis of origin, rainfall may be classified into three main types – the convectional, orographic or relief and the cyclonic or frontal. Conventional Rain

A combination of these four basic types can give rise to the following types of clouds: high clouds – cirrus, cirrostratus, cirrocumulus; middle clouds – altostratus and altocumulus; low clouds – stratocumulus and nimbostratus and clouds with extensive vertical development – cumulus and cumulonimbus.

The, air on being heated, becomes light and rises up in convection currents. As it rises, it expands and loses heat and consequently, condensation takes place and cumulous clouds are formed. With thunder and lightening, heavy rainfall takes place but this does not last

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long. Such rain is common in the summer or in the hotter part of the day. It is very common in the equatorial regions and interior parts of the continents, particularly in the northern hemisphere. Orographic Rain When the saturated air mass comes across a mountain, it is forced to ascend and as it rises, it expands; the temperature falls, and the moisture is condensed. The chief characteristic of this sort of rain is that the windward slopes receive greater rainfall. After giving rain on the windward side, when these winds reach the other slope, they descend, and their temperature rises. Then their capacity to take in moisture increases and hence, these leeward slopes remain rainless and dry. The area situated on the leeward side, which gets less rainfall is known as the rain-shadow area. It is also known as the relief rain. Cyclonic Rain You have already read about extra tropical cyclones and cyclonic rain in Chapter 10. Please consult Chapter 10 to understand cyclonic rainfall. World Distribution of Rainfall Different places on the earth’s surface receive different amounts of rainfall in a year and that too in different seasons. In general, as we proceed from the equator towards the poles, rainfall goes on decreasing steadily. The coastal areas of the world receive greater amounts of rainfall than the interior of

the continents. The rainfall is more over the oceans than on the landmasses of the world because of being great sources of water. Between the latitudes 350 and 400 N and S of the equator, the rain is heavier on the eastern coasts and goes on decreasing towards the west. But, between 450 and 650 N and S of equator, due to the westerlies, the rainfall is first received on the western margins of the continents and it goes on decreasing towards the east. Wherever mountains run parallel to the coast, the rain is greater on the coastal plain, on the windward side and it decreases towards the leeward side. On the basis of the total amount of annual precipitation, major precipitation regimes of the world are identified as follows. The equatorial belt, the windward slopes of the mountains along the western coasts in the cool temperate zone and the coastal areas of the monsoon land receive heavy rainfall of over 200 cm per annum. Interior continental areas receive moderate rainfall varying from 100 - 200 cm per annum. The coastal areas of the continents receive moderate amount of rainfall. The central parts of the tropical land and the eastern and interior parts of the temperate lands receive rainfall varying between 50 - 100 cm per annum. Areas lying in the rain shadow zone of the interior of the continents and high latitudes receive very low rainfall-less than 50 cm per annum. Seasonal distribution of rainfall provides an important aspect to judge its effectiveness. In some regions rainfall is distributed evenly throughout the year such as in the equatorial belt and in the western parts of cool temperate regions.

EXERCISES 1.

Multiple choice questions. (i)

Which one of the following is the most important constituent of the atmosphere for human beings? (a) Water vapour

(c) Dust particle

(b) Nitrogen

(d) Oxygen

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

(ii) Which one of the following process is responsible for transforming liquid into vapour? (a) Condensation

(c) Evaporation

(b) Transpiration

(d) Precipitation

(iii) The air that contains moisture to its full capacity :

(iv)

2.

(c) Absolute humidity

(b) Specific humidity

(d) Saturated air

Which one of the following is the highest cloud in the sky? (a) Cirrus

(c) Nimbus

(b) Stratus

(d) Cumulus

Answer the following questions in about 30 words. (i) (ii)

3.

(a) Relative humidity

Name the three types of precipitation. Explain relative humidity.

(iii)

Why does the amount of water vapour decreases rapidly with altitude?

(iv)

How are clouds formed? Classify them.

Answer the following questions in about 150 words. (i) (ii)

Discuss the salient features of the world distribution of precipitation. What are forms of condensation? Describe the process of dew and frost formation.

Project Work Browse through the newspaper from 1st June to 31st December and note the news about extreme rainfall in different parts of the country.

CHAPTER

WORLD CLIMATE AND CLIMATE CHANGE

T

related them to the distribution of vegetation and used these values for classifying the climates. It is an empirical classification based on mean annual and mean monthly temperature and precipitation data. He introduced the use of capital and small letters to designate climatic groups and types. Although developed in 1918 and modified over a period of time, Koeppen’s scheme is still popular and in use. Koeppen recognised five major climatic groups, four of them are based on temperature and one on precipitation. Table 12.1 lists the climatic groups and their characteristics according to Koeppen. The capital letters : A,C, D and E delineate humid climates and B dry climates. The climatic groups are subdivided into types, designated by small letters, based on seasonality of precipitation and temperature characteristics. The seasons of dryness are indicated by the small letters : f, m, w and s, where f corresponds to no dry season,

he world climate can be studied by organising information and data on climate and synthesising them in smaller units for easy understanding, description and analysis. Three broad approaches have been adopted for classifying climate. They are empirical, genetic and applied. Empirical classification is based on observed data, particularly on temperature and precipitation. Genetic classification attempts to organise climates according to their causes. Applied classification is for specific purpose.

KOEPP E N ’ S SCHEME CLIMATE

OF

CLASSIFICATION

OF

The most widely used classification of climate is the empirical climate classification scheme developed by V. Koeppen. Koeppen identified a close relationship between the distribution of vegetation and climate. He selected certain values of temperature and precipitation and

Table 12.1 : Climatic Groups According to Koeppen Group

Characteristics

A - Tropical

Average temperature of the coldest month is 18° C or higher

B - Dry Climates

Potential evaporation exceeds precipitation

C - Warm Temperate

The average temperature of the coldest month of the (Mid-latitude) climates years is higher than minus 3°C but below 18°C

D - Cold Snow Forest Climates

The average temperature of the coldest month is minus 3° C or below

E - Cold Climates

Average temperature for all months is below 10° C

H - High Land

Cold due to elevation

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

islands of East Indies. Significant amount of rainfall occurs in every month of the year as thunder showers in the afternoon. The temperature is uniformly high and the annual range of temperature is negligible. The maximum temperature on any day is around 30°C while the minimum temperature is around 20°C. Tropical evergreen forests with dense canopy cover and large biodiversity are found in this climate.

m - monsoon climate, w- winter dry season and s - summer dry season. The small letters a, b, c and d refer to the degree of severity of temperature. The B- Dry Climates are subdivided using the capital letters S for steppe or semi-arid and W for deserts. The climatic types are listed in Table 12.2. The distribution of climatic groups and types is shown in Table 12.1.

Table 12.2 : Climatic Types According to Koeppen Group A-Tropical Humid Climate

B-Dry Climate

C-Warm temperate (Midlatitude) Climates D-Cold Snowforest Climates E-Cold Climates H-Highland

Type

Letter Code

Characteristics

Tropical wet

Af

No dry season

Tropical monsoon

Am

Monsoonal, short dry season

Tropical wet and dry

Aw

Winter dry season

Subtropical steppe

BSh

Low-latitude semi arid or dry

Subtropical desert

BWh

Low-latitude arid or dry

Mid-latitude steppe

BSk

Mid-latitude semi arid or dry

Mid-latitude desert

BWk

Mid-latitude arid or dry

Humid subtropical

Cfa

No dry season, warm summer

Mediterranean

Cs

Dry hot summer

Marine west coast

Cfb

No dry season, warm and cool summer

Humid continental

Df

No dry season, severe winter

Subarctic

Dw

Winter dry and very severe

Tundra

ET

No true summer

Polar ice cap

EF

Perennial ice

Highland

H

Highland with snow cover

Group A : Tropical Humid Climates

Tropical Monsoon Climate (Am)

Tropical humid climates exist between Tropic of Cancer and Tropic of Capricorn. The sun being overhead throughout the year and the presence of Inter Tropical Convergence Zone (INTCZ) make the climate hot and humid. Annual range of temperature is very low and annual rainfall is high. The tropical group is divided into three types, namely (i) Af- Tropical wet climate; (ii) Am - Tropical monsoon climate; (iii) Aw- Tropical wet and dry climate.

Tropical monsoon climate (Am) is found over the Indian sub-continent, North Eastern part of South America and Northern Australia. Heavy rainfall occurs mostly in summer. Winter is dry. The detailed climatic account of this climatic type is given in the book on India: Physical Environment.

Tropical Wet Climate (Af) Tropical wet climate is found near the equator. The major areas are the Amazon Basin in South America, western equatorial Africa and the

Tropical Wet and Dry Climate (Aw) Tropical wet and dry climate occurs north and south of Af type climate regions. It borders with dry climate on the western part of the continent and Cf or Cw on the eastern part. Extensive Aw climate is found to the north and south of the Amazon forest in Brazil and adjoining parts

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of Bolivia and Paraguay in South America, Sudan and south of Central Africa. The annual rainfall in this climate is considerably less than that in Af and Am climate types and is variable also. The wet season is shorter and the dry season is longer with the drought being more severe. Temperature is high throughout the year and diurnal ranges of temperature are the greatest in the dry season. Deciduous forest and tree-shredded grasslands occur in this climate.

often causing famine. Rain occurs in short intense thundershowers in deserts and is ineffective in building soil moisture. Fog is common in coastal deserts bordering cold currents. Maximum temperature in the summer is very high. The highest shade temperature of 58° C was recorded at Al Aziziyah, Libya on 13 September 1922. The annual and diurnal ranges of temperature are also high. Warm Temperate (Mid-Latitude) Climates-C

Dry Climates : B Dry climates are characterised by very low rainfall that is not adequate for the growth of plants. These climates cover a very large area of the planet extending over large latitudes from 15° - 60° north and south of the equator. At low latitudes, from 15° - 30°, they occur in the area of subtropical high where subsidence and inversion of temperature do not produce rainfall. On the western margin of the continents, adjoining the cold current, particularly over the west coast of South America, they extend more equatorwards and occur on the coast land. In middle latitudes, from 35° - 60° north and south of equator, they are confined to the interior of continents where maritime-humid winds do not reach and to areas often surrounded by mountains. Dry climates are divided into steppe or semi-arid climate (BS) and desert climate (BW). They are further subdivided as subtropical steppe (BSh) and subtropical desert (BWh) at latitudes from 15° - 35° and mid-latitude steppe (BSk) and mid-latitude desert (BWk) at latitudes between 35° - 60°. Subtropical Steppe (BSh) and Subtropical Desert (BWh) Climates Subtropical steppe (BSh) and subtropical desert (BWh) have common precipitation and temperature characteristics. Located in the transition zone between humid and dry climates, subtropical steppe receives slightly more rainfall than the desert, adequate enough for the growth of sparse grasslands. The rainfall in both the climates is highly variable. The variability in the rainfall affects the life in the steppe much more than in the desert, more

Warm temperate (mid-latitude) climates extend from 30° - 50° of latitude mainly on the eastern and western margins of continents. These climates generally have warm summers with mild winters. They are grouped into four types: (i) Humid subtropical, i.e. dry in winter and hot in summer (Cwa); (ii) Mediterranean (Cs); (iii) Humid subtropical, i.e. no dry season and mild winter (Cfa); (iv) Marine west coast climate (Cfb). Humid Subtropical Climate (Cwa) Humid subtropical climate occurs poleward of Tropic of Cancer and Capricorn, mainly in North Indian plains and South China interior plains. The climate is similar to Aw climate except that the temperature in winter is warm. Mediterranean Climate (Cs) As the name suggests, Mediterranean climate occurs around Mediterranean sea, along the west coast of continents in subtropical latitudes between 30° - 40° latitudes e.g. — Central California, Central Chile, along the coast in south eastern and south western Australia. These areas come under the influence of sub tropical high in summer and westerly wind in winter. Hence, the climate is characterised by hot, dry summer and mild, rainy winter. Monthly average temperature in summer is around 25° C and in winter below 10°C. The annual precipitation ranges between 35 - 90 cm. Humid Subtropical (Cfa) Climate Humid subtropical climate lies on the eastern parts of the continent in subtropical latitudes. In this region the air masses are generally

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unstable and cause rainfall throughout the year. They occur in eastern United States of America, southern and eastern China, southern Japan, northeastern Argentina, coastal south Africa and eastern coast of Australia. The annual averages of precipitation vary from 75-150 cm. Thunderstorms in summer and frontal precipitation in winter are common. Mean monthly temperature in summer is around 27°C, and in winter it varies from 5°-12° C. The daily range of temperature is small.

Cold Climate with Dry Winters (Dw)

Marine West Coast Climate (Cfb)

Polar Climates (E)

Marine west coast climate is located poleward from the Mediterranean climate on the west coast of the continents. The main areas are: Northwestern Europe, west coast of North America, north of California, southern Chile, southeastern Australia and New Zealand. Due to marine influence, the temperature is moderate and in winter, it is warmer than for its latitude. The mean temperature in summer months ranges from 15°-20°C and in winter 4°-10°C. The annual and daily ranges of temperature are small. Precipitation occurs throughout the year. Precipitation varies greatly from 50-250cm.

Polar climates exist poleward beyond 70° latitude. Polar climates consist of two types: (i) Tundra (ET); (ii) Ice Cap (EF).

Cold climate with dry winter occurs mainly over Northeastern Asia. The development of pronounced winter anti cyclone and its weakening in summer sets in monsoon like reversal of wind in this region. Poleward summer temperatures are lower and winter temperatures are extremely low with many locations experiencing below freezing point temperatures for up to seven months in a year. Precipitation occurs in summer. The annual precipitation is low from 12-15 cm.

Tundra Climate (ET) The tundra climate (ET) is so called after the types of vegetation, like low growing mosses, lichens and flowering plants. This is the region of permafrost where the sub soil is permanently frozen. The short growing season and water logging support only low growing plants. During summer, the tundra regions have very long duration of day light. Ice Cap Climate (EF)

Cold Snow Forest Climates (D) Cold snow forest climates occur in the large continental area in the northern hemisphere between 40°-70° north latitudes in Europe, Asia and North America. Cold snow forest climates are divided into two types: (i) Df- cold climate with humid winter; (ii) Dw- cold climate with dry winter. The severity of winter is more pronounced in higher latitudes.

The ice cap climate (EF) occurs over interior Greenland and Antartica. Even in summer, the temperature is below freezing point. This area receives very little precipitation. The snow and ice get accumulated and the mounting pressure causes the deformation of the ice sheets and they break. They move as icebergs that float in the Arctic and Antarctic waters. Plateau Station , Antarctica ,79°S, portray this climate.

Cold Climate with Humid Winters (Df)

Highland Climates (H)

Cold climate with humid winter occurs poleward of marine west coast climate and mid latitude steppe. The winters are cold and snowy. The frost free season is short. The annual ranges of temperature are large. The weather changes are abrupt and short. Poleward, the winters are more severe.

Highland climates are governed by topography. In high mountains, large changes in mean temperature occur over short distances. Precipitation types and intensity also vary spatially across high lands. There is vertical zonation of layering of climatic types with elevation in the mountain environment.

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CLIMATE CHANGE The earlier chapters on climate summarised our understanding of climate as it prevails now. The type of climate we experience now might be prevailing over the last 10,000 years with minor and occasionally wide fluctuations. The planet earth has witnessed many variations in climate since the beginning. Geological records show alteration of glacial and inter-glacial periods. The geomorphological features, especially in high altitudes and high latitudes, exhibit traces of advances and retreats of glaciers. The sediment deposits in glacial lakes also reveal the occurrence of warm and cold periods. The rings in the trees provide clues about wet and dry periods. Historical records describe the vagaries in climate. All these evidences indicate that change in climate is a natural and continuous process. India also witnessed alternate wet and dry periods. Archaeological findings show that the Rajasthan desert experienced wet and cool climate around 8,000 B.C. The period 3,0001,700 B.C. had higher rainfall. From about 2,000-1,700 B.C., this region was the centre of the Harappan civilisation. Dry conditions accentuated since then. In the geological past, the earth was warm some 500-300 million years ago, through the Cambrian, Ordovician and Silurian periods. During the Pleistocene epoch, glacial and inter-glacial periods occurred, the last major peak glacial period was about 18,000 years ago. The present inter-glacial period started 10,000 years ago. Climate in the recent past Variability in climate occurs all the time. The nineties decade of the last century witnessed extreme weather events. The 1990s recorded the warmest temperature of the century and some of the worst floods around the world. The worst devastating drought in the Sahel region, south of the Sahara desert, from 1967-1977 is one such variability. During the 1930s, severe drought occurred in southwestern Great Plains of the United States, described as the dust bowl. Historical records of crop yield or

crop failures, of floods and migration of people tell about the effects of changing climate. A number of times Europe witnessed warm, wet, cold and dry periods, the significant episodes were the warm and dry conditions in the tenth and eleventh centuries, when the Vikings settled in Greenland. Europe witnessed “Little Ice Age” from 1550 to about 1850. From about 1885-1940 world temperature showed an upward trend. After 1940, the rate of increase in temperature slowed down. Causes of Climate Change The causes for climate change are many. They can be grouped into astronomical and terrestrial causes. The astronomical causes are the changes in solar output associated with sunspot activities. Sunspots are dark and cooler patches on the sun which increase and decrease in a cyclical manner. According to some meteorologists, when the number of sunspots increase, cooler and wetter weather and greater storminess occur. A decrease in sunspot numbers is associated with warm and drier conditions. Yet, these findings are not statistically significant. An another astronomical theory is Millankovitch oscillations, which infer cycles in the variations in the earth’s orbital characteristics around the sun, the wobbling of the earth and the changes in the earth’s axial tilt. All these alter the amount of insolation received from the sun, which in turn, might have a bearing on the climate. Volcanism is considered as another cause for climate change. Volcanic eruption throws up lots of aerosols into the atmosphere. These aerosols remain in the atmosphere for a considerable period of time reducing the sun’s radiation reaching the Earth’s surface. After the recent Pinatoba and El Cion volcanic eruptions, the average temperature of the earth fell to some extent for some years. The most important anthropogenic effect on the climate is the increasing trend in the concentration of greenhouse gases in the atmosphere which is likely to cause global warming.

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Global Warming Due to the presence of greenhouse gases, the atmosphere is behaving like a greenhouse. The atmosphere also transmits the incoming solar radiation but absorbs the vast majority of long wave radiation emitted upwards by the earth’s surface. The gases that absorb long wave radiation are called greenhouse gases. The processes that warm the atmosphere are often collectively referred to as the greenhouse effect. The term greenhouse is derived from the analogy to a greenhouse used in cold areas for preserving heat. A greenhouse is made up of glass. The glass which is transparent to incoming short wave solar radiation is opaque to outgoing long wave radiation. The glass, therefore, allows in more radiation and prevents the long wave radiation going outside the glass house, causing the temperature inside the glasshouse structure warmer than outside. When you enter a car or a bus, during summers, where windows are closed, you feel more heat than outside. Likewise during winter the vehicles with closed doors and windows remain warmer than the temperature outside. This is another example of the greenhouse effect.

Greenhouse Gases(GHGs) The primary GHGs of concern today are carbon dioxide (CO2), Chlorofluorocarbons (CFCs), methane (CH4), nitrous oxide (N2O) and ozone (O3). Some other gases such as nitric oxide (NO) and carbon monoxide (CO) easily react with GHGs and affect their concentration in the atmosphere. The effectiveness of any given GHG molecule will depend on the magnitude of the increase in its concentration, its life time in the atmosphere and the wavelength of radiation that it absorbs. The chlorofluorocarbons (CFCs) are highly effective. Ozone which absorbs ultra violet radiation in the stratosphere is very effective in absorbing terrestrial radiation when it is present in the lower troposphere. Another important point to be noted is that the more time the GHG molecule remains in the atmosphere, the longer

it will take for earth’s atmospheric system to recover from any change brought about by the latter. The largest concentration of GHGs in the atmosphere is carbon dioxide. The emission of CO 2 comes mainly from fossil fuel combustion (oil, gas and coal). Forests and oceans are the sinks for the carbon dioxide. Forests use CO 2 in their growth. So, deforestation due to changes in land use, also increases the concentration of Co2. The time taken for atmospheric CO2 to adjust to changes in sources to sinks is 20-50 years. It is rising at about 0.5 per cent annually. Doubling of concentration of CO2 over pre-industrial level is used as an index for estimating the changes in climate in climatic models. Chlorofluorocarbons (CFCs) are products of human activity. Ozone occurs in the stratosphere where ultra-violet rays convert oxygen into ozone. Thus, ultra violet rays do not reach the earth’s surface. The CFCs which drift into the stratosphere destroy the ozone. Large depletion of ozone occurs over Antarctica. The depletion of ozone concentration in the stratosphere is called the ozone hole. This allows the ultra violet rays to pass through the troposphere. International efforts have been initiated for reducing the emission of GHGs into the atmosphere. The most important one is the Kyoto protocol proclaimed in 1997. This protocol went into effect in 2005, ratified by 141 nations. Kyoto protocol bounds the 35 industrialised countries to reduce their emissions by the year 2012 to 5 per cent less than the levels prevalent in the year 1990. The increasing trend in the concentration of GHGs in the atmosphere may, in the long run, warm up the earth. Once the global warming sets in, it will be difficult to reverse it. The effect of global warming may not be uniform everywhere. Nevertheless, the adverse effect due to global warming will adversely affect the life supporting system. Rise in the sea level due to melting of glaciers and ice-caps and thermal expansion of the sea may inundate large parts of the coastal area and islands, leading to social problems. This is another cause for serious concern for the world

WORLD CLIMATE AND CLIMATE CHANGE

community. Efforts have already been initiated to control the emission of GHGs and to arrest the trend towards global warming. Let us hope the world community responds to this challenge and adopts a lifestyle that leaves behind a livable world for the generations to come. One of the major concerns of the world today is global warming. Let us look at how much the planet has warmed up from the temperature records. Temperature data are available from the middle of the 19th century mostly for western Europe. The reference period for this study is 1961-90. The temperature anomalies for the earlier and later periods are estimated from the average temperature for the period 1961-90. The annual average near -surface air temperature of the world is approximately 14°C. The time series show anomalies of

Write an explanatory note on “global warming”.

109

annual near surface temperature over land from 1856-2000, relative to the period 1961-90 as normal for the globe. An increasing trend in temperature was discernible in the 20th century. The greatest warming of the 20th century was during the two periods, 1901-44 and 1977-99. Over each of these two periods, global temperatures rose by about 0.4°C. In between, there was a slight cooling, which was more marked in the Northern Hemisphere. The globally averaged annual mean temperature at the end of the 20th century was about 0.6°C above that recorded at the end of the 19th century. The seven warmest years during the 1856-2000 were recorded in the last decade. The year 1998 was the warmest year, probably not only for the 20th century but also for the whole millennium.

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EXERCISES 1.

Multiple choice questions. (i) Which one of the following is suitable for Koeppen’s “A” type of climate? (a)

High rainfall in all the months

(b) Mean monthly temperature of the coldest month more than freezing point (c)

Mean monthly temperature of all the months more than 18o C

(d)

Average temperature for all the months below 10° C

(ii) Koeppen’s system of classification of climates can be termed as : (a) Applied

(b) Systematic

(c) Genetic

(d) Empirical

(iii) Most of the Indian Peninsula will be grouped according to Koeppen’s system under: (a) “Af”

(b) “BSh”

(c) “Cfb”

(d) “Am”

(iv) Which one of the following years is supposed to have recorded the warmest temperature the world over? (a) 1990

(b) 1998

(c) 1885

(d) 1950

(v) Which one of the following groups of four climates represents humid conditions?

2.

3.

(a)

A—B—C—E

(b)

A—C—D—E

(c)

B—C—D—E

(d)

A—C—D—F

Answer the following questions in about 30 words. (i)

Which two climatic variables are used by Koeppen for classification of the climate?

(ii)

How is the “genetic” system of classification different from the “empirical one”?

(iii)

Which types of climates have very low range of temperature?

(iv)

What type of climatic conditions would prevail if the sun spots increase?

Answer the following questions in about 150 words. (i)

Make a comparison of the climatic conditions between the “A” and “B” types of climate.

(ii)

What type of vegetation would you find in the “C” and “A” type(s) of climate?

(iii)

What do you understand by the term “Greenhouse Gases”? Make a list of greenhouse gases.

Project Work Collect information about Kyoto declaration related to global climate changes.

UNIT V WATER (OCEANS) This unit deals with •

Hydrological Cycle

•

Oceans — submarine relief; distribution of temperature and salinity; movements of ocean water-waves, tides and currents

CHAPTER

WATER (OCEANS)

C

an we think of life without water? It is said that the water is life. Water is an essential component of all life forms that exist over the surface of the earth. The creatures on the earth are lucky that it is a water planet, otherwise we all would have no existence. Water is a rare commodity in our solar system. There is no water on the sun or anywhere else in the solar system. The earth, fortunately has an abundant supply of water on its surface. Hence, our planet is called the ‘Blue Planet’.

HYDROLOGICAL CYCLE Water is a cyclic resource. It can be used and re-used. Water also undergoes a cycle from

the ocean to land and land to ocean. The hydrological cycle describes the movement of water on, in, and above the earth. The water cycle has been working for billions of years and all the life on earth depends on it. Next to air, water is the most important element required for the existence of life on earth. The distribution of water on earth is quite uneven. Many locations have plenty of water while others have very limited quantity. The hydrological cycle, is the circulation of water within the earth’s hydrosphere in different forms i.e. the liquid, solid and the gaseous phases. It also refers to the continuous exchange of water between the oceans,

Figure 13.1 : Hydrological Cycle

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Table 13.1 : Water on the Earth’s surface Reservoir

Volume (Million Cubic km )

Percentage of the Total

1,370

97.25

29

2.05

Oceans Ice Caps and Glaciers Groundwater

9.5

0.68

Lakes

0.125

0.01

Soil Moisture

0.065

0.005

Atmosphere

0.013

0.001

Streams and Rivers

0.0017

0.0001

Biosphere

0.0006

0.00004

Table 13.2 : Components and Processes of the Water Cycle Components

Processes

Water storage in oceans

Evaporation Evapotranspiration Sublimation

Water in the atmosphere

Condensation Precipitation

Water storage in ice and snow

Snowmelt runoff to streams

Surface runoff

Stream flow freshwater storage infiltration

Groundwater storage

Groundwater discharge springs

atmosphere, landsurface and subsurface and the organisms. Table 13.1 shows distribution of water on the surface of the earth. About 71 per cent of the planetary water is found in the oceans. The remaining is held as freshwater in glaciers and icecaps, groundwater sources, lakes, soil moisture, atmosphere, streams and within life. Nearly 59 per cent of the water that falls on land returns to the atmosphere through evaporation from over the oceans as well as from other places. The remainder runs-off on the surface, infiltrates into the ground or a part of it becomes glacier (Figure 13.1). It is to be noted that the renewable water on the earth is constant while the demand is increasing tremendously. This leads to water

crisis in different parts of the world — spatially and temporally. The pollution of river waters has further aggravated the crisis. How can you intervene in improving the water quality and augmenting the available quantity of water?

RELIEF

OF THE

OCEAN FLOOR

The oceans are confined to the great depressions of the earth’s outer layer. In this section, we shall see the nature of the ocean basins of the earth and their topography. The oceans, unlike the continents, merge so naturally into one another that it is hard to demarcate them. The geographers have divided the oceanic part of the earth into four oceans, namely the Pacific, the Atlantic, the Indian and the Arctic. The various seas, bays, gulfs and other inlets are parts of these four large oceans. A major portion of the ocean floor is found between 3-6 km below the sea level. The ‘land’ under the waters of the oceans, that is, the ocean floor exhibits complex and varied features as those observed over the land (Figure 13.2). The floors of the oceans are rugged with the world’s largest mountain ranges, deepest trenches and the largest plains. These features are formed, like those of the continents, by the factors of tectonic, volcanic and depositional processes. Divisions of the Ocean Floors The ocean floors can be divided into four major divisions: (i) the Continental Shelf; (ii) the Continental Slope; (iii) the Deep Sea Plain; (iv) the Oceanic Deeps. Besides, these divisions there are also major and minor relief features in the ocean floors like ridges, hills, sea mounts, guyots, trenches, canyons, etc. Continental Shelf The continental shelf is the extended margin of each continent occupied by relatively shallow seas and gulfs. It is the shallowest part of the ocean showing an average gradient of 1° or even less. The shelf typically ends at a very steep slope, called the shelf break. The width of the continental shelves vary from one ocean to another. The average width

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

of continental shelves is about 80 km. The shelves are almost absent or very narrow along some of the margins like the coasts of Chile, the west coast of Sumatra, etc. On the contrary, the Siberian shelf in the Arctic Ocean, the largest in the world, stretches to 1,500 km in width. The depth of the shelves also varies. It may be as shallow as 30 m in some areas while in some areas it is as deep as 600 m. The continental shelves are covered with variable thicknesses of sediments brought down by rivers, glaciers, wind, from the land and distributed by waves and currents. Massive sedimentary deposits received over a long time by the continental shelves, become the source of fossil fuels.

Continental Slope The continental slope connects the continental shelf and the ocean basins. It begins where the bottom of the continental shelf sharply drops off into a steep slope. The gradient of the slope region varies between 2-5°. The depth of the slope region varies between 200 and 3,000 m. The slope boundary indicates the end of the continents. Canyons and trenches are observed in this region. Deep Sea Plain Deep sea plains are gently sloping areas of the ocean basins. These are the flattest and smoothest regions of the world. The depths vary between 3,000 and 6,000m. These plains are covered with fine-grained sediments like clay and silt. Oceanic Deeps or Trenches These areas are the deepest parts of the oceans. The trenches are relatively steep sided, narrow basins. They are some 3-5 km deeper than the surrounding ocean floor. They occur at the bases of continental slopes and along island arcs and are associated with active volcanoes and strong earthquakes. That is why they are very significant in the study of plate movements. As many as 57 deeps have been explored so far; of which 32 are in the Pacific Ocean; 19 in the Atlantic Ocean and 6 in the Indian Ocean. Minor Relief Features Apart from the above mentioned major relief features of the ocean floor, some minor but significant features predominate in different parts of the oceans. Mid-Oceanic Ridges

Figure 13.2 : Relief features of ocean floors

A mid-oceanic ridge is composed of two chains of mountains separated by a large depression. The mountain ranges can have peaks as high as 2,500 m and some even reach above the ocean’s surface. Iceland, a part of the midAtlantic Ridge, is an example.

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WATER (OCEANS)

Seamount It is a mountain with pointed summits, rising from the seafloor that does not reach the surface of the ocean. Seamounts are volcanic in origin. These can be 3,000-4,500 m tall. The Emperor seamount, an extension of the Hawaiian Islands in the Pacific Ocean, is a good example. Submarine Canyons These are deep valleys, some comparable to the Grand Canyon of the Colorado river. They are sometimes found cutting across the continental shelves and slopes, often extending from the mouths of large rivers. The Hudson Canyon is the best known canyon in the world. Guyots It is a flat topped seamount. They show evidences of gradual subsidence through stages to become flat topped submerged mountains. It is estimated that more than 10,000 seamounts and guyots exist in the Pacific Ocean alone. Atoll These are low islands found in the tropical oceans consisting of coral reefs surrounding a central depression. It may be a part of the sea (lagoon), or sometimes form enclosing a body of fresh, brackish, or highly saline water.

TEMPERATURE

OF

OCEAN WATERS

This section deals with the spatial and vertical variations of temperature in various oceans. Ocean waters get heated up by the solar energy just as land. The process of heating and cooling of the oceanic water is slower than land. Factors Affecting Temperature Distribution The factors which affect the distribution of temperature of ocean water are : (i) Latitude : the temperature of surface water decreases from the equator towards the poles because the amount of insolation decreases poleward. (ii) Unequal distribution of land and water : the oceans in the northern hemisphere

receive more heat due to their contact with larger extent of land than the oceans in the southern hemisphere. (iii) Prevailing wind : the winds blowing from the land towards the oceans drive warm surface water away form the coast resulting in the upwelling of cold water from below. It results into the longitudinal variation in the temperature. Contrary to this, the onshore winds pile up warm water near the coast and this raises the temperature. (iv) Ocean currents : warm ocean currents raise the temperature in cold areas while the cold currents decrease the temperature in warm ocean areas. Gulf stream (warm current) raises the temperature near the eastern coast of North America and the West Coast of Europe while the Labrador current (cold current) lowers the temperature near the north-east coast of North America. All these factors influence the temperature of the ocean currents locally. The enclosed seas in the low latitudes record relatively higher temperature than the open seas; whereas the enclosed seas in the high latitudes have lower temperature than the open seas. Horizontal and Vertical Distribution of Temperature The temperature-depth profile for the ocean water shows how the temperature decreases with the increasing depth. The profile shows a boundary region between the surface waters of the ocean and the deeper layers. The boundary usually begins around 100 - 400 m below the sea surface and extends several hundred of m downward (Figure 13.3). This boundary region, from where there is a rapid decrease of temperature, is called the thermocline. About 90 per cent of the total volume of water is found below the thermocline in the deep ocean. In this zone, temperatures approach 0° C. The temperature structure of oceans over middle and low latitudes can be described as a three-layer system from surface to the bottom. The first layer represents the top layer of

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

warm oceanic water and it is about 500m thick with temperatures ranging between 20° and 25° C. This layer, within the tropical region, is present throughout the year but in mid latitudes it develops only during summer. The second layer called the thermocline layer lies below the first layer and is characterised by rapid decrease in temperature with increasing depth. The thermocline is 500 -1,000 m thick.

hemisphere record relatively higher temperature than in the southern hemisphere. The highest temperature is not recorded at the equator but slightly towards north of it. The average annual temperatures for the northern and southern hemisphere are around 19° C and 16° C respectively. This variation is due to the unequal distribution of land and water in the northern and southern hemispheres. Figure 13.4 shows the spatial pattern of surface temperature of the oceans. It is a well known fact that the maximum temperature of the oceans is always at their surfaces because they directly receive the heat from the sun and the heat is transmitted to the lower sections of the oceans through the process of conduction. It results into decrease of temperature with the increasing depth, but the rate of decrease is not uniform throughout. The temperature falls very rapidly up to the depth of 200 m and thereafter, the rate of decrease of temperature is slowed down.

SALINITY

Figure 13.3 : Thermocline

The third layer is very cold and extends upto the deep ocean floor. In the Arctic and Antartic circles, the surface water temperatures are close to 0° C and so the temperature change with the depth is very slight. Here, only one layer of cold water exists, which extends from surface to deep ocean floor. The average temperature of surface water of the oceans is about 27°C and it gradually decreases from the equator towards the poles. The rate of decrease of temperature with increasing latitude is generally 0.5°C per latitude. The average temperature is around 22°C at 20° latitudes, 14° C at 40° latitudes and 0° C near poles. The oceans in the northern

OF

OCEAN WATERS

All waters in nature, whether rain water or ocean water, contain dissolved mineral salts. Salinity is the term used to define the total content of dissolved salts in sea water (Table 13.4). It is calculated as the amount of salt (in gm) dissolved in 1,000 gm (1 kg) of seawater. It is usually expressed as parts per thousand (o/oo) or ppt. Salinity is an important property of sea water. Salinity of 24.7 o/oo has been considered as the upper limit to demarcate ‘brackish water’. Factors affecting ocean salinity are mentioned below: (i) The salinity of water in the surface layer of oceans depend mainly on evaporation and precipitation. (ii) Surface salinity is greatly influenced in coastal regions by the fresh water flow from rivers, and in polar regions by the processes of freezing and thawing of ice. (iii) Wind, also influences salinity of an area by transferring water to other areas. (iv) The ocean currents contribute to the salinity variations. Salinity, temperature and density of water are interrelated. Hence, any change in the temperature or density influences the salinity of an area.

117

WATER (OCEANS)

Figure 13.4 : Spatial pattern of surface temperature (°C) of the oceans

Highest salinity in water bodies Lake Van in Turkey (330 o/oo), Dead Sea (238 o/oo), Great Salt Lake (220 o/oo) Table 13.4 : Dissolved Salts in Sea Water (gm of Salt per kg of Water) Chlorine Sodium Sulphate Magnesium Calcium Potassium Bicarbonate Bromine Borate Strontium

HORIZONTAL DISTRIBUTION

18.97 10.47 2.65 1.28 0.41 0.38 0.14 0.06 0.02 0.01

OF

SALINITY

The salinity for normal open ocean ranges between 33o/oo and 37 o/oo. In the land locked

Red Sea, it is as high as 41o/oo, while in the estuaries and the Arctic, the salinity fluctuates from 0 - 35 o/oo, seasonally. In hot and dry regions, where evaporation is high, the salinity sometimes reaches to 70 o/oo. The salinity variation in the Pacific Ocean is mainly due to its shape and larger areal extent. Salinity decreases from 35 o/oo - 31 o/oo on the western parts of the northern hemisphere because of the influx of melted water from the Arctic region. In the same way, after 15° - 20° south, it decreases to 33 o/oo . The average salinity of the Atlantic Ocean is around 36 o/oo. The highest salinity is recorded between 15° and 20° latitudes. Maximum salinity (37 o/oo) is observed between 20° N and 30° N and 20° W - 60° W. It gradually decreases towards the north. The North Sea, in spite of its location in higher latitudes, records higher salinity due to more saline water brought by the North Atlantic Drift. Baltic Sea records low salinity due to influx of river waters in large quantity. The Mediterranean Sea

118

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Figure13.5 : Surface salinity of the World’s Oceans

records higher salinity due to high evaporation. Salinity is, however, very low in Black Sea due to enormous fresh water influx by rivers. See the atlas to find out the rivers joining Black Sea. The average salinity of the Indian Ocean is o 35 /oo. The low salinity trend is observed in the Bay of Bengal due to influx of river water by the river Ganga. On the contrary, the Arabian Sea shows higher salinity due to high evaporation and low influx of fresh water. Figure 13.5 shows the salinity of the World’s oceans. Vertical Distribution of Salinity Salinity changes with depth, but the way it changes depends upon the location of the sea. Salinity at the surface increases by the loss of

water to ice or evaporation, or decreased by the input of fresh waters, such as from the rivers. Salinity at depth is very much fixed, because there is no way that water is ‘lost’, or the salt is ‘added.’ There is a marked difference in the salinity between the surface zones and the deep zones of the oceans. The lower salinity water rests above the higher salinity dense water. Salinity, generally, increases with depth and there is a distinct zone called the halocline, where salinity increases sharply. Other factors being constant, increasing salinity of seawater causes its density to increase. High salinity seawater, generally, sinks below the lower salinity water. This leads to stratification by salinity.

EXERCISES 1.

Multiple choice questions. (i)

Identify the element which is not a part of the hydrological cycle (a) Evaporation (b) Hydration

(c) Precipitation (d) Condensation

119

WATER (OCEANS)

(ii) The average depth of continental slope varies between (a) 2-20m

(c) 20-200m

(b) 200-2,000m

(d) 2,000-20,000m

(iii) Which one of the following is not a minor relief feature in the oceans:

(iv)

(v)

2.

(c) Oceanic Deep

(b) Atoll

(d) Guyot

Salinity is expressed as the amount of salt in grams dissolved in sea water per (a) 10 gm

(c) 100 gm

(b) 1,000 gm

(d) 10,000 gm

Which one of the following is the smallest ocean: (a) Indian Ocean

(c) Atlantic Ocean

(b) Arctic Ocean

(d) Pacific Ocean

Answer the following questions in about 30 words. (i) (ii)

Why do we call the earth a Blue Planet? What is a continental margin?

(iii)

List out the deepest trenches of various oceans.

(iv)

What is a thermocline?

(v) (vi) 3.

(a) Seamount

When you move into the ocean what thermal layers would you encounter? Why the temperature varies with depth? What is salinity of sea water?

Answer the following questions in about 150 words. (i) (ii)

How are various elements of the hydrological cycle interrelated? Examine the factors that influence the temperature distribution of the oceans.

Project Work (i) (ii)

Consult the atlas and show ocean floor relief on the outline of the world map. Identify the areas of mid oceanic ridges from the Indian Ocean.

CHAPTER

MOVEMENTS

T

he ocean water is dynamic. Its physical characteristics like temperature, salinity, density and the external forces like of the sun, moon and the winds influence the movement of ocean water. The horizontal and vertical motions are common in ocean water bodies. The horizontal motion refers to the ocean currents and waves. The vertical motion refers to tides. Ocean currents are the continuous flow of huge amount of water in a definite direction while the waves are the horizontal motion of water. Water moves ahead from one place to another through ocean currents while the water in the waves does not move, but the wave trains move ahead. The vertical motion refers to the rise and fall of water in the oceans and seas. Due to attraction of the sun and the moon, the ocean water is raised up and falls down twice a day. The upwelling of cold water from subsurface and the sinking of surface water are also forms of vertical motion of ocean water.

WAVES Waves are actually the energy, not the water as such, which moves across the ocean surface. Water particles only travel in a small circle as a wave passes. Wind provides energy to the waves. Wind causes waves to travel in the ocean and the energy is released on shorelines. The motion of the surface water seldom affects the stagnant deep bottom water of the oceans. As a wave approaches the beach, it slows down. This is due to the friction occurring between the dynamic water and the sea floor. And, when the depth of water is less than half the

OF

OCEAN WATER

wavelength of the wave, the wave breaks. The largest waves are found in the open oceans. Waves continue to grow larger as they move and absorb energy from the wind. Most of the waves are caused by the wind driving against water. When a breeze of two knots or less blows over calm water, small ripples form and grow as the wind speed increases until white caps appear in the breaking waves. Waves may travel thousands of km before rolling ashore, breaking and dissolving as surf. A wave’s size and shape reveal its origin. Steep waves are fairly young ones and are probably formed by local wind. Slow and steady waves originate from far away places, possibly from another hemisphere. The maximum wave height is determined by the strength of the wind, i.e. how long it blows and the area over which it blows in a single direction. Waves travel because wind pushes the water body in its course while gravity pulls the crests of the waves downward. The falling water pushes the former troughs upward, and the

Figure14.1 : Motion of waves and water molecules

MOVEMENTS OF OCEAN WATER

wave moves to a new position (Figure 14.1). The actual motion of the water beneath the waves is circular. It indicates that things are carried up and forward as the wave approaches, and down and back as it passes. Characteristics of Waves Wave crest and trough : The highest and lowest points of a wave are called the crest and trough respectively. Wave height : It is the vertical distance from the bottom of a trough to the top of a crest of a wave. Wave amplitude : It is one-half of the wave height. Wave period : It is merely the time interval between two successive wave crests or troughs as they pass a fixed point.

121

attraction of the moon is less as it is farther away, the centrifugal force causes tidal bulge on the other side (Figure 14.2). The ‘tide-generating’ force is the difference between these two forces; i.e. the gravitational attraction of the moon and the centrifugal force. On the surface of the earth, nearest the moon, pull or the attractive force of the moon is greater than the centrifugal force, and so there is a net force causing a bulge towards the moon. On the opposite side of the earth, the attractive force is less, as it is farther away from the moon, the centrifugal force is dominant. Hence, there is a net force away from the moon. It creates the second bulge away from the moon. On the surface of the earth, the horizontal tide generating forces are more important than the vertical forces in generating the tidal bulges.

Wavelength : It is the horizontal distance between two successive crests. Wave speed : It is the rate at which the wave moves through the water, and is measured in knots. Wave frequency : It is the number of waves passing a given point during a onesecond time interval.

TIDES The periodical rise and fall of the sea level, once or twice a day, mainly due to the attraction of the sun and the moon, is called a tide. Movement of water caused by meteorological effects (winds and atmospheric pressure changes) are called surges. Surges are not regular like tides. The study of tides is very complex, spatially and temporally, as it has great variations in frequency, magnitude and height. The moon’s gravitational pull to a great extent and to a lesser extent the sun’s gravitational pull, are the major causes for the occurrence of tides. Another factor is centrifugal force, which is the force that acts to counter the balance the gravity. Together, the gravitational pull and the centrifugal force are responsible for creating the two major tidal bulges on the earth. On the side of the earth facing the moon, a tidal bulge occurs while on the opposite side though the gravitational

Figure14.2 : Relation between gravitational forces and tides

The tidal bulges on wide continental shelves, have greater height. When tidal bulges hit the mid-oceanic islands they become low. The shape of bays and estuaries along a coastline can also magnify the intensity of tides. Funnel-shaped bays greatly change tidal magnitudes. When the tide is channelled between islands or into bays and estuaries they are called tidal currents.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

122

Tides of Bay of Fundy, Canada The highest tides in the world occur in the Bay of Fundy in Nova Scotia, Canada. The tidal bulge is 15 - 16 m. Because there are two high tides and two low tides every day (roughly a 24 hour period); then a tide must come in within about a six hour period. As a rough estimate, the tide rises about 240 cm an hour (1,440 cm divided by 6 hours). If you have walked down a beach with a steep cliff alongside (which is common there), make sure you watch the tides. If you walk for about an hour and then notice that the tide is coming in, the water will be over your head before you get back to where you started!

Types of Tides Tides vary in their frequency, direction and movement from place to place and also from time to time. Tides may be grouped into various types based on their frequency of occurrence in one day or 24 hours or based on their height. Tides based on Frequency Semi-diurnal tide : The most common tidal pattern, featuring two high tides and two low tides each day. The successive high or low tides are approximately of the same height. Diurnal tide : There is only one high tide and one low tide during each day. The successive high and low tides are approximately of the same height. Mixed tide : Tides having variations in height are known as mixed tides. These tides generally occur along the west coast of North America and on many islands of the Pacific Ocean. Tides based on the Sun, Moon and the Earth Positions The height of rising water (high tide) varies appreciably depending upon the position of sun and moon with respect to the earth. Spring tides and neap tides come under this category.

Spring tides : The position of both the sun and the moon in relation to the earth has direct bearing on tide height. When the sun, the moon and the earth are in a straight line, the height of the tide will be higher. These are called spring tides and they occur twice a month, one on full moon period and another during new moon period. Neap tides : Normally, there is a seven day interval between the spring tides and neap tides. At this time the sun and moon are at right angles to each other and the forces of the sun and moon tend to counteract one another. The Moon’s attraction, though more than twice as strong as the sun’s, is diminished by the counteracting force of the sun’s gravitational pull. Once in a month, when the moon’s orbit is closest to the earth (perigee), unusually high and low tides occur. During this time the tidal range is greater than normal. Two weeks later, when the moon is farthest from earth (apogee), the moon’s gravitational force is limited and the tidal ranges are less than their average heights. When the earth is closest to the sun (perihelion), around 3rd January each year, tidal ranges are also much greater, with unusually high and unusually low tides. When the earth is farthest from the sun (aphelion), around 4th July each year, tidal ranges are much less than average. The time between the high tide and low tide, when the water level is falling, is called the ebb. The time between the low tide and high tide, when the tide is rising, is called the flow or flood. Importance of Tides Since tides are caused by the earth-moon-sun positions which are known accurately, the tides can be predicted well in advance. This helps the navigators and fishermen plan their activities. Tidal flows are of great importance in navigation. Tidal heights are very important, especially harbours near rivers and within estuaries having shallow ‘bars’ at the entrance, which prevent ships and boats from entering into the harbour. Tides are also helpful in

MOVEMENTS OF OCEAN WATER

desilting the sediments and in removing polluted water from river estuaries. Tides are used to generate electrical power (in Canada, France, Russia, and China). A 3 MW tidal power project at Durgaduani in Sunderbans of West Bengal is under way.

OCEAN CURRENTS Ocean currents are like river flow in oceans. They represent a regular volume of water in a definite path and direction. Ocean currents are influenced by two types of forces namely : (i) primary forces that initiate the movement of water; (ii) secondary forces that influence the currents to flow. The primary forces that influence the currents are: (i) heating by solar energy; (ii) wind; (iii) gravity; (iv) coriolis force. Heating by solar energy causes the water to expand. That is why, near the equator the ocean water is about 8 cm higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope. Wind blowing on the surface of the ocean pushes the water to move. Friction between the wind and the water surface affects the movement of the water body in its course. Gravity tends to pull the water down to pile and create gradient variation. The Coriolis force intervenes and causes the water to move to the right in the northern hemisphere and to the left in the southern hemisphere. These large accumulations of water and the flow around them are called Gyres. These produce large circular currents in all the ocean basins. Characteristics of Ocean Currents Currents are referred to by their “drift”. Usually, the currents are strongest near the surface and may attain speeds over five knots. At depths, currents are generally slow with speeds less than 0.5 knots. We refer to the speed of a current as its “drift.” Drift is measured in terms of knots. The strength of a current refers to the speed of the current. A fast current is considered strong. A current is usually strongest at the surface and decreases in strength (speed) with depth. Most currents have speeds less than or equal to 5 knots.

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Differences in water density affect vertical mobility of ocean currents. Water with high salinity is denser than water with low salinity and in the same way cold water is denser than warm water. Denser water tends to sink, while relatively lighter water tends to rise. Cold-water ocean currents occur when the cold water at the poles sinks and slowly moves towards the equator. Warm-water currents travel out from the equator along the surface, flowing towards the poles to replace the sinking cold water. Types of Ocean Currents The ocean currents may be classified based on their depth as surface currents and deep water currents : (i) surface currents constitute about 10 per cent of all the water in the ocean, these waters are the upper 400 m of the ocean; (ii) deep water currents make up the other 90 per cent of the ocean water. These waters move around the ocean basins due to variations in the density and gravity. Deep waters sink into the deep ocean basins at high latitudes, where the temperatures are cold enough to cause the density to increase. Ocean currents can also be classified based on temperature : as cold currents and warm currents: (i) cold currents bring cold water into warm water areas. These currents are usually found on the west coast of the continents in the low and middle latitudes (true in both hemispheres) and on the east coast in the higher latitudes in the Northern Hemisphere; (ii) warm currents bring warm water into cold water areas and are usually observed on the east coast of continents in the low and middle latitudes (true in both hemispheres). In the northern hemisphere they are found on the west coasts of continents in high latitudes. Major Ocean Currents Major ocean currents are greatly influenced by the stresses exerted by the prevailing winds and coriolis force. The oceanic circulation pattern roughly corresponds to the earth’s atmospheric circulation pattern. The air circulation over the oceans in the middle latitudes is mainly anticyclonic (more pronounced in the southern hemisphere than in the northern hemisphere). The oceanic circulation pattern also corresponds with the same. At higher latitudes,

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

124

Fig.14.3 : Major currents in the Pacific, Atlantic and Indian oceans

where the wind flow is mostly cyclonic, the oceanic circulation follows this pattern. In regions of pronounced monsoonal flow, the monsoon winds influence the current movements. Due to the coriolis force, the warm currents from low latitudes tend to move to the right in the northern hemisphere and to their left in the southern hemisphere. The oceanic circulation transports heat from one latitude belt to another in a manner similar to the heat transported by the general circulation of the atmosphere. The cold waters of the Arctic and Antarctic circles move towards warmer water in tropical and equatorial regions, while the warm waters of the lower latitudes move polewards. The major currents in the different oceans are shown in Figure14.3. Prepare a list of currents which are found in Pacific, Atlantic and Indian Oceans. How is the movement of currents is influenced by prevailing winds? Give some examples from Figure14.3.

Effects of Ocean Currents Ocean currents have a number of direct and indirect influences on human activities. West coasts of the continents in tropical and subtropical latitudes (except close to the equator) are bordered by cool waters. Their average temperatures are relatively low with a narrow diurnal and annual ranges. There is fog, but generally the areas are arid. West coasts of the continents in the middle and higher latitudes are bordered by warm waters which cause a distinct marine climate. They are characterised by cool summers and relatively mild winters with a narrow annual range of temperatures. Warm currents flow parallel to the east coasts of the continents in tropical and subtropical latitudes. This results in warm and rainy climates. These areas lie in the western margins of the subtropical anti-cyclones. The mixing of warm and cold currents help to replenish the oxygen and favour the growth of planktons, the primary food for fish population. The best fishing grounds of the world exist mainly in these mixing zones.

MOVEMENTS OF OCEAN WATER

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EXERCISES 1.

Multiple choice questions. (i) Upward and downward movement of ocean water is known as the : (a) tide

(c) wave

(b) current

(d) none of the above

(ii) Spring tides are caused : (a)

As result of the moon and the sun pulling the earth gravitationally in the same direction.

(b)

As result of the moon and the sun pulling the earth gravitationally in the opposite direction.

(c)

Indention in the coast line.

(d)

None of the above.

(iii) The distance between the earth and the moon is minimum when the moon is in :

(iv)

2.

(c) Perihelion

(b) Perigee

(d) Apogee

The earth reaches its perihelion in: (a) October

(c) July

(b) September

(d) January

Answer the following questions in about 30 words. (i) (ii)

What are waves? Where do waves in the ocean get their energy from?

(iii)

What are tides?

(iv)

How are tides caused?

(v) 3.

(a) Aphelion

How are tides related to navigation?

Answer the following questions in about 150 words. (i) (ii)

How do currents affect the temperature? How does it affect the temperature of coastal areas in the N. W. Europe? What are the causes of currents?

Project Work (i)

Visit a lake or a pond and observe the movement of waves. Throw a stone and notice how waves are generated. Draw the diagram of a wave and measure its length, distance and amplitude and record them in your note.

(ii)

Take a globe and a map showing the currents of the oceans. Discuss why certain currents are warm or cold and why they deflect in certain places and examine the reasons.

UNIT VI LIFE

ON THE

EARTH

This unit deals with •

Biosphere — importance of plants and other organisms; ecosystems, bio-geo chemical cycle and ecological balance; biodiversity and conservation

CHAPTER

LIFE

ON THE

EARTH

B

y now you might have realised that all units of this book have acquainted you with the three major realms of the environment, that is, the lithosphere, the atmosphere and the hydrosphere. You know that living organisms of the earth, constituting the biosphere, interact with other environmental realms. The biosphere includes all the living components of the earth. It consists of all plants and animals, including all the microLife on the earth is found almost everywhere. Living organisms are found from the poles to the equator, from the bottom of the sea to several km in the air, from freezing waters to dry valleys, from under the sea to underground water lying below the earth’s surface.

organisms that live on the planet earth and their interactions with the surrounding environment. Most of the organisms exist on the lithosphere and/or the hydrosphere as well as in the atmosphere. There are also many organisms that move freely from one realm to the other. The biosphere and its components are very significant elements of the environment. These elements interact with other components of the natural landscape such as land, water and soil. They are also influenced by the atmospheric elements such as the temperature, rainfall, moisture and sunlight. The interactions of biosphere with land, air and water are important to the growth, development and evolution of the organism.

E COLOGY You have been reading about ecological and environmental problems in newspapers and magazines. Have you ever thought what ecology is? The environment as you know, is made up of abiotic and biotic components. It would be interesting to understand how the diversity of life-forms is maintained to bring a kind of balance. This balance is maintained in a particular proportion so that a healthy interaction between the biotic and the abiotic components goes on. The interactions of a particular group of organisms with abiotic factors within a particular habitat resulting in clearly defined energy flows and material cycles on land, water and air, are called ecological systems. The term ecology is derived from the Greek word ‘oikos’ meaning ‘house’, combined with the word ‘logy’ meaning the ‘science of’ or ‘the study of ’. Literally, ecology is the study of the earth as a ‘household’, of plants, human beings, animals and micro-organisms. They all live together as interdependent components. A German zoologist Ernst Haeckel, who used the term as ‘oekologie’ in 1869, became the first person to use the term ‘ecology’. The study of interactions between life forms (biotic) and the physical environment (abiotic) is the science of ecology. Hence, ecology can be defined as a scientific study of the interactions of organisms with their physical environment and with each other.

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

A habitat in the ecological sense is the totality of the physical and chemical factors that constitute the general environment. A system consisting of biotic and abiotic components is known as ecosystem. All these components in ecosystem are inter related and interact with each other. Different types of ecosystems exist with varying ranges of environmental conditions where various plants and animal species have got adapted through evolution. This phenomenon is known as ecological adaptation. Types of Ecosystems Ecosystems are of two major types: terrestrial and aquatic. Terrestrial ecosystem can be further be classified into ‘biomes’. A biome is a plant and animal community that covers a large geographical area. The boundaries of different biomes on land are determined mainly by climate. Therefore, a biome can be defined as the total assemblage of plant and animal species interacting within specific conditions. These include rainfall, temperature, humidity and soil conditions. Some of the major biomes of the world are: forest, grassland, desert and tundra biomes. Aquatic ecosystems can be classed as marine and freshwater ecosystems. Marine ecosystem includes the oceans, coastal estuaries and coral reefs. Freshwater

ecosystem includes lakes, ponds, streams, marshes and bogs. Structure and Functions of Ecosystems The structure of an ecosystem involves a description of the available plant and animal species. From a structural point of view, all ecosystems consist of abiotic and biotic factors. Abiotic factors include rainfall, temperature, sunlight, atmospheric humidity, soil conditions, inorganic substances (carbon dioxide, water, nitrogen, calcium, phosphorus, potassium, etc.). Biotic factors include the producers, (primary, secondary, tertiary) the consumers and the decomposers. The producers include all the green plants, which manufacture their own food through photosynthesis. The primary consumers include herbivorous animals like deer, goats, mice and all plant-eating animals. The carnivores include all the flesh-eating animals like snakes, tigers and lions. Certain carnivores that feed also on carnivores are known as top carnivores like hawks and mongooses. Decomposers are those that feed on dead organisms (for example, scavengers like vultures and crows), and further breaking down of the dead matter by other decomposing agents like bacteria and various microorganisms.

Figure 15.1 : Structure and functions of ecosystems

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LIFE ON THE EARTH

The producers are consumed by the primary consumers whereas the primary consumers are, in turn, being eaten by the secondary consumers. Further, the secondary consumers are consumed by the tertiary consumers. The decomposers feed on the dead at each and every level. They change them into various substances such as nutrients, organic and inorganic salts essential for soil fertility. Organisms of an ecosystem are linked together through a foodchain (Figure 15.1). For example, a plant eating beetle feeding on a paddy stalk is eaten by a frog, which is, in turn, eaten by a snake, which is then consumed by a hawk. This sequence of eating and being eaten and the resultant transfer of energy from one level to another is known as the food-chain. Transfer of energy that occurs during the process of a foodchain from one level to another is known as flow of energy. However, food-chains are not isolated from one another. For example, a mouse feeding on grain may be eaten by different secondary consumers (carnivores) and these carnivores may be eaten by other different tertiary consumers (top carnivores). In such situations, each of the carnivores may consume more than one type of prey. As a result, the food- chains get interlocked with one another. This interconnecting network of species is known as food web. Generally, two types of food-chains are recognised: grazing food-chain and detritus food-chain. In a grazing food-chain, the first level starts with plants as producers and ends with carnivores as consumers as the last level, with the herbivores being at the intermediate level. There is a loss of energy at each level which may be through respiration, excretion or decomposition. The levels involved in a foodchain range between three to five and energy is lost at each level. A detritus food-chain is based on autotrophs energy capture initiated by grazing animals and involves the decomposition or breaking down of organic wastes and dead matter derived from the grazing food-chain. Types of Biomes In the earlier paragraphs, you have learnt the meaning of the term ‘biome’. Let us now try to identify the major biomes of the world. There are five major biomes — forest, desert, grassland,

aquatic and altitudinal biomes. Some features of these biomes are given in Table 15.1. Biogeochemical Cycles The sun is the basic source of energy on which all life depends. This energy initiates life processes in the biosphere through photosynthesis, the main source of food and energy for green plants. During photosynthesis, carbon dioxide is converted into organic compounds and oxygen. Out of the total solar insolation that reaches the earth’s surface, only a very small fraction (0.1 per cent) is fixed in photosynthesis. More than half is used for plant respiration and the remaining part is temporarily stored or is shifted to other portions of the plant. Life on earth consists of a great variety of living organisms. These living organisms exist and survive in a diversity of associations. Such survival involves the presence of systemic flows such as flows of energy, water and nutrients. These flows show variations in different parts of the world, in different seasons of the year and under varying local circumstances. Studies have shown that for the last one billion years, the atmosphere and hydrosphere have been composed of approximately the same balance of chemical components. This balance of the chemical elements is maintained by a cyclic passage through the tissues of plants and animals. The cycle starts by absorbing the chemical elements by the organism and is returned to the air, water and soil through decomposition. These cycles are largely energised by solar insolation. These cyclic movements of chemical elements of the biosphere between the organism and the environment are referred to as biogeochemical cycles. Bio refers to living organisms and geo to rocks, soil, air and water of the earth. There are two types of biogeochemical cycles : the gaseous and the sedimentary cycle. In the gaseous cycle, the main reservoir of nutrients is the atmosphere and the ocean. In the sedimentary cycle, the main reservoir is the soil and the sedimentary and other rocks of the earth’s crust. The Water Cycle All living organisms, the atmosphere and the lithosphere maintain between them a

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Table 15.1 : World Biomes Biomes

Subtypes

Forest

A. 1. 2. B. C.

Desert

Hot and Dry A. desert B. Semi arid desert B. C. Coastal desert D. Cold desert C. D. A.

Tropical Equitorial Deciduous Temperate Boreal

B.

Tropical Savannah Temperate Steppe

B.

Soil

Flora and Fauna

A1. Temp. 20-25°C, evenly distributed A2. Temp. 25-30°C, Rainfall, ave. ann. 1,000mm, seasonal B. Temp. 20-30° C, Rainfall evenly distributed 7501,500mm, Welldefined seasons and distinct winter. C. Short moist moderately warm summers and long cold dry winter; very low temperatures. Precipitation mostly snowfall 400 -1,000mm

A1. Acidic, poor in nutrients A2. Rich in nutrients B. Fertile, en-riched with decaying litter C. Acidic and poor in nutrients, thin soil cover

A1. M u l t i - l a y e r e d canopy tall and large trees A2. Less dense, trees of medium height; many varieties coexis t. Insects, bats, birds and mammals are common species in both B. Moderately dense broad leaved trees. With less diversity of plant species. Oack, Beach, Maple etc. are some common species. Squirrels, rabbits, skunks, birds, black bears, mountain lions etc. C. Evergreen conifers like pine, fur and spruce etc. Wood peckers, hawks, bears, wolves, deer, hares and bats are common animals

S a h a r a , Kalahari, Marusthali, Rub-el-Khali Marginal areas of hot deserts Atacama Tundra climatic regions

A. Temp. 20 - 45°C. B. 21 - 38°C. C. 15 - 35°C. D. 2 - 25°C A-D Rainfall is less than 50 mm

Rich in nutrients with little or no organic matter

A-C. Scanty vegetation; few large mammals, insects, reptiles and birds D. Rabbits, rats, antelopes and ground squirrels

Large areas of A f r i c a , Australia, South America and India P a r t s of Eurasia and North America

A.

A.

A.

A1. 10° N-S A2. 10° - 25° N-S B. Eastern North America, N.E. Asia, Western and Central Europe C. Broad belt of Eurasia and North America, parts of Siberia, Alaska, Canada and Scandinavia

A.

Grassland A.

Climatic Characteristics

Regions

B.

Warm hot climates, Rainfall 500-1,250 mm Hot summers and cold winter. Rainfall 500 900 mm

B.

Porous with thin layer of humus. Thin flocculated soil, rich in bases

B.

Grasses; trees and large shrubs absent; giraffes zebras, buffalos, leopards, hyenas, elephants, mice, moles, snakes and worms etc., are common animals Grasses; occasional trees such as cottonwoods, oaks and willows; gazelles, zebras, rhin-

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LIFE ON THE EARTH

oceros, wild horses, lions, varieties of birds, worms, snakes etc., are common animals Aquatic

A. B.

Freshwater A. Marine B.

Altitudinal

———

Lakes, streams, A-B Temperatures vary A. Water, swamps rivers and widely with cooler air and marshes wetlands temperatures and Oceans, coral high humidity B.Water, tidal reefs, lagoons swamps and and estuaries marshes

Slopes of high mountain ranges like the Himalayas, the Andes and the Rockies

Temperature and precipitation vary depending upon latitudinal zone

circulation of water in solid, liquid or gaseous form referred to as the water or hydrologic cycle (Chapter 13 of this book).

Regolith over slopes

Algal and other aquatic and marine plant communities with varieties of water dwelling animals

Deciduous to tundra vegetation varying according to altitude

dioxide and are returned to the atmosphere (Figure 15.2).

The Carbon Cycle Carbon is one of the basic elements of all living organisms. It forms the basic constituent of all the organic compounds. The biosphere contains over half a million carbon compounds in them. The carbon cycle is mainly the conversion of carbon dioxide. This conversion is initiated by the fixation of carbon dioxide from the atmosphere through photosynthesis. Such conversion results in the production of carbohydrate, glucose that may be converted to other organic compounds such as sucrose, starch, cellulose, etc. Here, some of the carbohydrates are utilised directly by the plant itself. During this process, more carbon dioxide is generated and is released through its leaves or roots during the day. The remaining carbohydrates not being utilised by the plant become part of the plant tissue. Plant tissues are either being eaten by the herbivorous animals or get decomposed by the microorganisms. The herbivores convert some of the consumed carbohydrates into carbon dioxide for release into the air through respiration. The micro-organisms decompose the remaining carbohydrates after the animal dies. The carbohydrates that are decomposed by the micro-organisms then get oxidised into carbon

Figure 15.2 : Carbon Cycle

The Oxygen Cycle Oxygen is the main by-product of photosynthesis. It is involved in the oxidation of carbohydrates with the release of energy, carbon dioxide and water. The cycling of oxygen is a highly complex process. Oxygen occurs in a number of chemical forms and combinations. It combines with nitrogen to form nitrates and with many other minerals and elements to form various oxides such as the iron oxide, aluminium oxide and others. Much of oxygen is produced from the decomposition of water molecules by sunlight

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

during photosynthesis and is released in the atmosphere through transpiration and respiration processes of plants. The Nitrogen Cycle Nitrogen is a major constituent of the atmosphere comprising about seventy-nine per cent of the atmospheric gases. It is also an essential constituent of different organic compounds such as the amino acids, nucleic acids, proteins, vitamins and pigments. Only a few types of organisms like certain species of soil bacteria and blue green algae are capable of utilising it directly in its gaseous form. Generally, nitrogen is usable only after it is fixed. Ninety per cent of fixed nitrogen is biological. The principal source of free nitrogen is the action of soil micro-organisms and associated plant roots on atmospheric nitrogen found in pore spaces of the soil. Nitrogen can also be fixed in the atmosphere by lightning and cosmic radiation. In the oceans, some marine animals can fix it. After atmospheric nitrogen has been fixed into an available form, green plants can assimilate it. Herbivorous animals feeding on plants, in turn, consume some of it. Dead plants and animals, excretion of nitrogenous wastes are converted into nitrites by the action of bacteria present in the soil. Some bacteria can even convert nitrites into nitrates that can be used again by green plants. There are still other types of bacteria capable of converting nitrates into free nitrogen, a process known as denitrification (Figure 15.3).

Figure 15.3 : Nitrogen Cycle

Other Mineral Cycles Other than carbon, oxygen, nitrogen and hydrogen being the principal geochemical components of the biosphere, many other minerals also occur as critical nutrients for plant and animal life. These mineral elements required by living organisms are obtained initially from inorganic sources such as phosphorus, sulphur, calcium and potassium. They usually occur as salts dissolved in soil water or lakes, streams and seas. Mineral salts come directly from the earth’s crust by weathering where the soluble salts enter the water cycle, eventually reaching the sea. Other salts are returned to the earth’s surface through sedimentation, and after weathering, they again enter the cycle. All living organisms fulfill their mineral requirements from mineral solutions in their environments. Other animals receive their mineral needs from the plants and animals they consume. After the death of living organisms, the minerals are returned to the soil and water through decomposition and flow. Ecological Balance Ecological balance is a state of dynamic equilibrium within a community of organisms in a habitat or ecosystem. It can happen when the diversity of the living organisms remains relatively stable. Gradual changes do take place but that happens only through natural succession. It can also be explained as a stable balance in the numbers of each species in an ecosystem. This occurs through competition and cooperation between different organisms where population remains stable. This balance is brought about by the fact that certain species compete with one another determined by the environment in which they grow. This balance is also attained by the fact that some species depend on others for their food and sustenance. Such accounts are encountered in vast grasslands where the herbivorous animals (deer, zebras, buffaloes, etc.) are found in plenty. On the other hand, the carnivorous animals (tigers, lions, etc.) that are not usually in large numbers, hunt and feed on the herbivores, thereby controlling their population. In the plants, any disturbance in the native forests such as clearing the forest for shifting cultivation usually brings about a

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LIFE ON THE EARTH

change in the species distribution. This change is due to competition where the secondary forest species such as grasses, bamboos or pines overtakes the native species changing the original forest structure. This is called succession. Ecological balance may be disturbed due to the introduction of new species, natural hazards or human causes. Human interference has affected the balance of plant communities leading to disturbances in the ecosystems. Such disturbances bring about numerous secondary successions. Human pressure on the earth’s resources has put a heavy toll on

the ecosystem. This has destroyed its originality and has caused adverse effects to the general environment. Ecological imbalances have brought many natural calamities like floods, landslides, diseases, erratic climatic occurrences, etc. There is a very close relationship between the plant and animal communities within particular habitats. Diversity of life in a particular area can be employed as an indicator of the habitat factor. Proper knowledge and understanding of such factors provide a strong base for protecting and conserving the ecosystems.

EXERCISES 1.

Multiple choice questions. (i) Which one of the following is included in biosphere? (a) only plants

(c) only animals

(b) all living and non-living organisms

(d) all living organisms

(ii) Tropical grasslands are also known as : (a) the prairies

(c) the steppes

(b) the savannas

(d) none of the above

(iii) Oxygen combines with iron found in the rocks to form :

(iv)

2.

(a) iron carbonate

(c) iron oxides

(b) iron nitrites

(d) iron sulphate

During photosynthesis, carbon dioxide combines with water in the presence of sunlight to form : (a) proteins

(c) carbohydrates

(b) amino acids

(d) vitamins

Answer the following questions in about 30 words. (i) What do you understand by the term ‘ecology’? (ii) What is an ecological system? Identify the major types of ecosystems in the world. (iii) What is a food-chain? Give one example of a grazing food-chain identifying the various levels. (iv) What do you understand by the term ‘food web’? Give examples. (v) What is a biome?

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

3.

Answer the following questions in about 150 words. (i) What are bio-geochemical cycles? Explain how nitrogen is fixed in the atmosphere. (ii) What is an ecological balance? Discuss the important measures needed to prevent ecological imbalances.

Project Work (i) Show the distribution of the different biomes on the outline map of the world with a note highlighting the important characteristics of each biome. (ii) Make a note of trees, shrubs and perennial plants in your school campus and devote half a day to observe the types of birds which come to the garden. Can you describe the diversity of birds?

CHAPTER

BIODIVERSITY

AND

CONSERVATION

Y

ou have already learnt about the geomorphic processes particularly weathering and depth of weathering mantle in different climatic zones. See the Figure 6.2 in Chapter 6 in order to recapitulate. You should know that this weathering mantle is the basis for the diversity of vegetation and hence, the biodiversity. The basic cause for such weathering variations and resultant biodiversity is the input of solar energy and water. No wonder that the areas that are rich in these inputs are the areas of wide spectrum of biodiversity. Biodiversity as we have today is the result of 2.5-3.5 billion years of evolution. Before the advent of humans, our earth supported more biodiversity than in any other period. Since, the emergence of humans, however, biodiversity has begun a rapid decline, with one species after another bearing the brunt of extinction due to overuse. The number of species globally vary from 2 million to 100 million, with 10 million being the best estimate. New species are regularly discovered most of which are yet to be classified (an estimate states that about 40 per cent of fresh water fishes from South America are not classified yet). Tropical forests are very rich in bio-diversity.

Biodiversity is a system in constant evolution, from a view point of species, as well as from view point of an individual organism. The average half-life of a species is estimated at between one and four million years, and 99 per cent of the species that have ever lived on

the earth are today extinct. Biodiversity is not found evenly on the earth. It is consistently richer in the tropics. As one approaches the polar regions, one finds larger and larger populations of fewer and fewer species. Biodiversity itself is a combination of two words, Bio (life) and diversity (variety). In simple terms, biodiversity is the number and variety of organisms found within a specified geographic region. It refers to the varieties of plants, animals and micro-organisms, the genes they contain and the ecosystems they form. It relates to the variability among living organisms on the earth, including the variability within and between the species and that within and between the ecosystems. Biodiversity is our living wealth. It is a result of hundreds of millions of years of evolutionary history. Biodiversity can be discussed at three levels : (i) Genetic diversity; (ii) Species diversity; (iii) Ecosystem diversity. Genetic Diversity Genes are the basic building blocks of various life forms. Genetic biodiversity refers to the variation of genes within species. Groups of individual organisms having certain similarities in their physical characteristics are called species. Human beings genetically belong to the homo sapiens group and also differ in their characteristics such as height, colour, physical appearance, etc., considerably. This is due to genetic diversity. This genetic diversity is essential for a healthy breeding of population of species.

136

Species Diversity This refers to the variety of species. It relates to the number of species in a defined area. The diversity of species can be measured through its richness, abundance and types. Some areas are more rich in species than others. Areas rich in species diversity are called hotspots of diversity (Figure 16.5). Ecosystem Diversity You have studied about the ecosystem in the earlier chapter. The broad differences between ecosystem types and the diversity of habitats and ecological processes occurring within each ecosystem type constitute the ecosystem diversity. The ‘boundaries’ of communities (associations of species) and ecosystems are not very rigidly defined. Thus, the demarcation of ecosystem boundaries is difficult and complex.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY

ecosystem evolves and sustains without any reason. That means, every organism, besides extracting its needs, also contributes something of useful to other organisms. Can you think of the way we, humans contribute to the sustenance of ecosystems. Species capture and store energy, produce and decompose organic materials, help to cycle water and nutrients throughout the ecosystem, fix atmospheric gases and help regulate the climate. These functions are important for ecosystem function and human survival. The more diverse an ecosystem, better are the chances for the species to survive through adversities and attacks, and consequently, is more productive. Hence, the loss of species would decrease the ability of the system to maintain itself. Just like a species with a high genetic diversity, an ecosystem with high biodiversity may have a greater chance of adapting to environmental change. In other words, the more the variety of species in an ecosystem, the more stable the ecosystem is likely to be. Economic Role of Biodiversity

Figure 16.1 : Grasslands and sholas in Indira Gandhi National Park, Annamalai, Western Ghats — an example of ecosystem diversity

Importance of Biodiversity Biodiversity has contributed in many ways to the development of human culture and, in turn, human communities have played a major role in shaping the diversity of nature at the genetic, species and ecological levels. Biodiversity plays the following roles: ecological, economic and scientific. Ecological Role of Biodiversity Species of many kinds perform some function or the other in an ecosystem. Nothing in an

For all humans, biodiversity is an important resource in their day-to-day life. One important part of biodiversity is ‘crop diversity’, which is also called agro-biodiversity. Biodiversity is seen as a reservoir of resources to be drawn upon for the manufacture of food, pharmaceutical, and cosmetic products. This concept of biological resources is responsible for the deterioration of biodiversity. At the same time, it is also the origin of new conflicts dealing with rules of division and appropriation of natural resources. Some of the important economic commodities that biodiversity supplies to humankind are: food crops, livestock, forestry, fish, medicinal resources, etc. Scientific Role of Biodiversity Biodiversity is important because each species can give us some clue as to how life evolved and will continue to evolve. Biodiversity also helps in understanding how life functions and the role of each species in sustaining

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BIODIVERSITY AND CONSERVATION

ecosystems of which we are also a species. This fact must be drawn upon every one of us so that we live and let other species also live their lives. It is our ethical responsibility to consider that each and every species along with us have an intrinsic right to exist. Hence, it is morally wrong to voluntarily cause the extinction of any species. The level of biodiversity is a good indicator of the state of our relationships with other living species. In fact, the concept of biodiversity is an integral part of many human cultures.

LOSS

OF

The International Union of Conservation of Nature and Natural Resources (IUCN) has classified the threatened species of plants and animals into three categories for the purpose of their conservation. Endangered Species It includes those species which are in danger of extinction. The IUCN publishes information about endangered species world-wide as the Red List of threatened species.

BIODIVERSITY

Since the last few decades, growth in human population has increased the rate of consumption of natural resources. It has accelerated the loss of species and habitation in different parts of the world. Tropical regions which occupy only about one-fourth of the total area of the world, contain about threefourth of the world human population. Overexploitation of resources and deforestation have become rampant to fulfil the needs of large population. As these tropical rain forests contain 50 per cent of the species on the earth, destruction of natural habitats have proved disastrous for the entire biosphere. Natural calamities such as earthquakes, floods, volcanic eruptions, forest fires, droughts, etc. cause damage to the flora and fauna of the earth, bringing change the biodiversity of respective affected regions. Pesticides and other pollutants such as hydrocarbons and toxic heavy metals destroy the weak and sensitive species. Species which are not the natural inhabitants of the local habitat but are introduced into the system, are called exotic species. There are many examples when a natural biotic community of the ecosystem suffered extensive damage because of the introduction of exotic species. During the last few decades, some animals like tigers, elephants, rhinoceros, crocodiles, minks and birds were hunted mercilessly by poachers for their horn, tusks, hides, etc. It has resulted in the rendering of certain types of organisms as endangered category.

Figure 16.2 : Red Panda — an endangered species

Figure 16.3 : Zenkeria Sebastinei — a critically endangered grass in Agasthiyamalai peak (India)

Vulnerable Species This includes the species which are likely to be in danger of extinction in near future if the factors threatening to their extinction continue. Survival of these species is not assured as their population has reduced greatly.

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

Rare Species Population of these species is very small in the world; they are confined to limited areas or thinly scattered over a wider area.

Figure 16.4 : Humbodtia decurrens Bedd — highly rare endemic tree of Southern Western Ghats (India)

CONSERVATION

OF

BIODIVERSITY

Biodiversity is important for human existence. All forms of life are so closely interlinked that disturbance in one gives rise to imbalance in the others. If species of plants and animals become endangered, they cause degradation in the environment, which may threaten human being’s own existence. There is an urgent need to educate people to adopt environment-friendly practices and reorient their activities in such a way that our development is harmonious with other life forms and is sustainable. There is an increasing consciousness of the fact that such conservation with sustainable use is possible only with the involvement and cooperation of local communities and individuals. For this, the development of institutional structures at local levels is necessary. The critical problem is not merely the conservation of species nor the habitat but the continuation of process of conservation. The Government of India along with 155 other nations have signed the Convention of Biodiversity at the Earth Summit held at Riode Janeiro, Brazil in June 1992. The world conservation strategy has suggested the following steps for biodiversity conservation:

(i) Efforts should be made to preserve the species that are endangered. (ii) Prevention of extinction requires proper planning and management. (iii) Varieties of food crops, forage plants, timber trees, livestock, animals and their wild relatives should be preserved; (iv) Each country should identify habitats of wild relatives and ensure their protection. (v) Habitats where species feed, breed, rest and nurse their young should be safeguarded and protected. (vi) International trade in wild plants and animals be regulated. To protect, preserve and propagate the variety of species within natural boundaries, the Government of India passed the Wild Life (Protection) Act, 1972, under which national parks and sanctuaries were established and biosphere reserves declared. Details of these biosphere reserves are given in the book India: Physical Environment (NCERT, 2006). There are some countries which are situated in the tropical region; they possess a large number of the world’s species diversity. They are called mega diversity centres. There are 12 such countries, namely Mexico, Columbia, Ecuador, Peru, Brazil, Zaire, Madagascar, China, India, Malaysia, Indonesia and Australia in which these centres are located (Figure 16.5). In order to concentrate resources on those areas that are most vulnerable, the International Union for the Conservation of Nature and Natural Resources (IUCN) has identified certain areas as biodiversity hotspots. Hotspots are defined according to their vegetation. Plants are important because these determine the primary productivity of an ecosystem. Most, but not all, of the hotspots rely on speciesrich ecosystems for food, firewood, cropland, and income from timber. In Madagascar, for example, about 85 per cent of the plants and animals are not only found nowhere else in the world, but its people are also among the world’s poorest and rely on slash and burn agriculture for subsistence farming. Other hotspots in wealthy countries are facing

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BIODIVERSITY AND CONSERVATION

Figure 16.5 : Ecological ‘hotspots’ in the world

different types of pressures. The islands of Hawaii have many unique plants and animals

that are threatened by introduced species and land development.

EXERCISES 1.

Multiple choice questions. (i) Conservation of biodiversity is important for : (a) Animals

(c) Plants

(b) Animals and plants

(d) All organisms

(ii) Threatened species are those which : (a) threaten others (b) Lion and tiger (c) are abundant in number (d) are suffering from the danger of extinction (iii) National parks and sanctuaries are established for the purpose of : (a) Recreation

(c) Pets

(b) Hunting

(d) Conservation

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FUNDAMENTALS OF PHYSICAL GEOGRAPHY

(iv)

Biodiversity is richer in : (a) Tropical Regions (b) Polar Regions

(v)

2.

(d) Oceans

In which one of the following countries, the ‘Earth Summit’ was held? (a) the UK

(c) Brazil

(b) Mexico

(d) China

Answer the following questions in about 30 words. (i) (ii)

What is biodiversity? What are the different levels of biodiversity?

(iii)

What do you understand by ‘hotspots’?

(iv)

Discuss briefly the importance of animals to human kind.

(v) 3.

(c) Temperate Regions

What do you understand by ‘exotic species’?

Answer the following questions in about 150 words. (i) (ii)

What are the roles played by biodiversity in the shaping of nature? What are the major factors that are responsible for the loss of biodiversity? What steps are needed to prevent them?

Project Work Collect the names of national parks, sanctuaries and biosphere reserves of the state where your school is located and show their location on the map of India.

C ONTENTS FOREWORD

iii 1-6

UNIT I : INTRODUCTION 1.

India — Location

2

UNIT II : PHYSIOGRAPHY

7-31

2.

Structure and Physiography

3.

Drainage System

8 21

UNIT III : CLIMATE, VEGETATION

AND

SOIL

32-75

4.

Climate

33

5.

Natural Vegetation

57

6.

Soils

68

UNIT IV : NATURAL HAZARDS CONSEQUENCES 7.

AND

AND

DISASTERS: CAUSES,

MANAGEMENT

Natural Hazards and Disasters

APPENDICES I.

76-93

77 94-98

STATES, THEIR CAPITALS, NUMBER OF DISTRICTS, AREA AND POPULATION

94

UNION TERRITORIES, THEIR CAPITALS, AREA AND POPULATION

95

III.

IMPORTANT RIVER BASINS

96

IV.

STATE/UNION TERRITORY WISE FOREST COVER

97

NATIONAL PARKS

98

II.

V.

GLOSSARY

OF INDIA

99-100

UNIT I INTRODUCTION This unit deals with • Location — space relations and India’s place in the world

CHAPTER

INDIA – LOCATION

Y

ou have already seen the map of India in the previous classes. Now you closely examine the map of India (Figure 1.1). Mark the southernmost and northernmost latitudes and the easternmost and westernmost longitudes. The mainland of India, extends from Kashmir in the north to Kanniyakumari in the south and Arunachal Pradesh in the east to Gujarat in the west. India’s territorial limit further extends towards the sea upto 12 nautical miles (about 21.9 km) from the coast. (See the box for conversion). Statute mile Nautical mile 1 Statute mile 1 Nautical mile

= = = =

63,360 inches 72,960 inches about 1.6 km (1.584 km) about 1.8 km (1.852 km)

Our southern boundary extends upto 6°45' N latitude in the Bay of Bengal. Let us try to analyse the implications of having such a vast longitudinal and latitudinal extent. If you work out the latitudinal and longitudinal extent of India, they are roughly about 30 degrees, whereas the actual distance measured from north to south extremity is 3,214 km, and that from east to west is only 2,933 km. What is the reason for this difference? Consult Chapter 3 on the topic Latitude, Longitude and Time in the book

Practical Work in Geography – Part I (NCERT, 2006) to find out. This difference is based on the fact that the distance between two longitudes decreases towards the poles whereas the distance between two latitudes remains the same everywhere. Find out the distance between two latitudes? From the values of latitude, it is understood that the southern part of the country lies within the tropics and the northern part lies in the sub-tropical zone or the warm temperate zone. This location is responsible for large variations in land forms, climate, soil types and natural vegetation in the country. Now, let us observe the longitudinal extent and its implications on the Indian people. From the values of longitude, it is quite discernible that there is a variation of nearly 30 degrees, which causes a time difference of nearly two hours between the easternmost and the westernmost parts of our country. You are familiar with the concept of Indian Standard Time (IST). What is the use of the standard meridian? While the sun rises in the northeastern states about two hours earlier as compared to Jaisalmer, the watches in Dibrugarh, Imphal in the east and Jaisalmer, Bhopal or Chennai in the other parts of India show the same time. Why does this happen?

There is a general understanding among the countries of the world to select the standard meridian in multiples of 7°30' of longitude. That is why 82°30' E has been selected as the ‘standard meridian’ of India. Indian Standard Time is ahead of Greenwich Mean Time by 5 hours and 30 minutes. There are some countries where there are more than one standard meridian due to their vast east-to-west extent. For example, the USA has seven time zones.

3

INDIA – LOCATION

Figure 1.1 : India : Administrative Divisions

Figure 1.2 : Location of India in the Eastern World

4 INDIA : PHYSICAL ENVIRONMENT

5

INDIA – LOCATION

Name a few place in India through which the standard meridian passes? India with its area of 3.28 million sq. km accounts for 2.4 per cent of the world’s land surface area and stands as the seventh largest country in the world. Find out the names of the countries which are larger than India.

SIZE The size of India has endowed her with great physical diversity. Thus, you may appreciate the presence of lofty mountains in the north; large rivers such as Ganga, Brahmaputra, Mahanadi, Krishna, Godavari and Kaveri; green forested hills in northeast and south India; and the vast sandy expanse of Marusthali. You may further appreciate that bounded by the Himalayas in the north, Hindukush and Sulaiman ranges in the northwest, Purvachal hills in the north-east and by the large expanse of the Indian ocean in the south, it forms a great geographic entity known as the Indian subcontinent. It includes the countries — Pakistan, Nepal, Bhutan, Bangladesh and India. The Himalayas, together with other ranges, have acted as a formidable physical barrier in the past. Except for a few mountain passes such as the Khyber, the Bolan, the Shipkila, the Nathula, the Bomdila, etc. it was difficult to cross it. It has contributed towards the evolving of a unique regional identity of the Indian subcontinent. By referring to the physical map of India you can now describe the physical variations which you would come across while travelling

from Kashmir to Kanniyakumari and from Jaisalmer in Rajasthan to Imphal in Manipur. Peninsular part of India extends towards the Indian Ocean. This has provided the country with a coastline of 6,100 km in the mainland and 7,517 km in the entire geographical coast of the mainland plus the island groups Andaman and Nicobar located in the Bay of Bengal and the Lakshadweep in the Arabian Sea. Thus India, as a country, is a physically diverse land providing occurrence of varied resources.

INDIA

AND ITS

NEIGHBOURS

Examine the location map of India (Figure 1.2). You will notice that India is located in the south-central part of the continent of Asia, bordering the Indian ocean and its two arms extending in the form of Bay of Bengal and the Arabian Sea. This maritime location of Peninsular India has provided links to its neighbouring regions through the sea and air routes. Prepare a list of India’s neighbouring countries by consulting the map. Sri Lanka and Maldives are the two island countries located in the Indian Ocean, which are our neighbours. Sri Lanka is separated from India by the Gulf of Mannar and Palk Strait. Differentiate between a Gulf and a Strait

Do you think that physical barrier is a hindrance in interaction with our neighbouring countries in modern times? Give some examples how we have overcome these difficulties in the present day.

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i) Which one of the following latitudinal extent is relevant for the extent of India’s area? (a) 8°41'N - 35°7'N (c) 8°4'N - 35°6'N (b) 8°4'N - 37°6'N (d) 6°45'N - 37°6'N (ii) Which one of the following countries shares the longest land frontier with India? (a) Bangladesh (b) China

(c) Pakistan (d) Myanmar

6

INDIA : PHYSICAL ENVIRONMENT

(iii) Which one of the following countries is larger in area than India? (a) China (c) France (b) Egypt (d) Iran (iv) Which one of the following longitudes is the standard meridian for India? (a) 69°30'E (c) 75°30'E (b) 82°30'E (d) 90°30'E 2.

Answer the following questions in about 30 words. (i) Does India need to have more than one standard time? If yes, why do you think so? (ii) What are the implications of India having a long coastline? (iii) How is the latitudinal spread of India advantageous to her? (iv) While the sun rises earlier in the east, say Nagaland and also sets earlier, how do the watches at Kohima and New Delhi show the same time?

Project/Activity Activity based on Appendix I (Teachers may help in the exercises by explaining and getting it done by the students). (i) On a graph paper, plot the number of districts in Madhya Pradesh, Karnataka, Meghalaya, Goa, Kerala, Haryana. Do the number of districts have some relationship with the area of the state? (ii) Which state amongst Uttar Pradesh, West Bengal, Gujarat, Arunachal Pradesh, Tamil Nadu, Tripura, Rajasthan and Jammu and Kashmir is the most thickly populated and which one is the least densely populated? (iii) Find out the relationship between the area of the state and the number of districts. (iv) Identify the states with coastal boundaries. (v) Arrange the states from west to east which have only land boundary. Activity based on Appendix II (i) List the Union Territories which have coastal location. (ii) How do you explain the variation in the area and population of NCT Delhi and the Andaman and Nicobar Islands? (iii) On a graph paper, draw a bar diagram to show the area and population of all the Union Territories.

UNIT II PHYSIOGRAPHY This unit deals with • Structure and Relief; physiographic divisions • Drainage systems: concept of water sheds — the Himalayan

and the Peninsular

CHAPTER

STRUCTURE

D

o you know that our earth also has a history. The earth and its landforms that we see today have evolved over a very long time. Current estimation shows that the earth is approximately 460 million years old. Over these long years, it has undergone many changes brought about primarily by the endogenic and exogenic forces. These forces have played a significant role in giving shape to various surface and subsurface features of the earth. You have already studied about the Plate Tectonics and the movement of the Earth’s plates in the book Fundamentals of Physical Geography (NCERT, 2006). Do you know that the Indian plate was to the south of the equator millions of years ago? Do you also know that it was much larger in size and the Australian plate was a part of it? Over millions of years, this plate broke into many parts and the Australian plate moved towards the southeastern direction and the Indian plate to the north. Can you map different phases in the movement of the Indian plate? This northward movement of the Indian plate is still continuing and it has significant consequences on the physical environment of the Indian subcontinent. Can you name some important consequences of the northward movement of the Indian plate? It is primarily through the interplay of these endogenic and exogenic forces and lateral movements of the plates that the present geological structure and geomorphologic processes active in the Indian subcontinent came into existence. Based on the variations in its geological structure and formations, India can be divided into three geological divisions. These geological regions broadly follow the physical features:

AND

PHYSIOGRAPHY

(i) The Penisular Block (ii) The Himalayas and other Peninuslar Mountains (iii) Indo-Ganga-Brahmaputra Plain.

THE PENINSULAR BLOCK The northern boundary of the Peninsular Block may be taken as an irregular line running from Kachchh along the western flank of the Aravali Range near Delhi and then roughly parallel to the Yamuna and the Ganga as far as the Rajmahal Hills and the Ganga delta. Apart from these, the Karbi Anglong and the Meghalaya Plateau in the northeast and Rajasthan in the west are also extensions of this block. The northeastern parts are separated by the Malda fault in West Bengal from the Chotanagpur plateau. In Rajasthan, the desert and other desert–like features overlay this block. The Peninsula is formed essentially by a great complex of very ancient gneisses and granites, which constitutes a major part of it. Since the Cambrian period, the Peninsula has been standing like a rigid block with the exception of some of its western coast which is submerged beneath the sea and some other parts changed due to tectonic activity without affecting the original basement. As a part of the Indo-Australian Plate, it has been subjected to various vertical movements and block faulting. The rift valleys of the Narmada, the Tapi and the Mahanadi and the Satpura block mountains are some examples of it. The Peninsula mostly consists of relict and residual mountains like the Aravali hills, the Nallamala hills, the Javadi hills, the Veliconda hills, the

9

STRUCTURE AND PHYSIOGRAPHY

Palkonda range and the Mahendragiri hills, etc. The river valleys here are shallow with low gradients. You are aware of the method of calculating the gradient as a part of your study of the book Practical Work in Geography– Part I (NCERT, 2006). Can you calculate the gradient of the Himalayan and the Peninsular rivers and draw the comparisons? Most of the east flowing rivers form deltas before entering into the Bay of Bengal. The deltas formed by the Mahanadi, the Krishna, the Kaveri and the Godavari are important examples.

THE HIMALAYAS AND OTHER PENINSULAR MOUNTAINS The Himalayas along with other Peninsular mountains are young, weak and flexible in their geological structure unlike the rigid and stable Peninsular Block. Consequently, they are still subjected to the interplay of exogenic and endogenic forces, resulting in the development of faults, folds and thrust plains. These mountains are tectonic in origin, dissected by fast-flowing rivers which are in their youthful stage. Various landforms like gorges, V-shaped valleys, rapids, waterfalls, etc. are indicative of this stage.

during the third phase of the Himalayan mountain formation approximately about 64 million years ago. Since then, it has been gradually filled by the sediments brought by the Himalayan and Peninsular rivers. Average depth of alluvial deposits in these plains ranges from 1,000-2,000 m. It is evident from the above discussion that there are significant variations among the different regions of India in terms of their geological structure, which has far-reaching impact upon other related aspects. Variations in the physiography and relief are important among these. The relief and physiography of India has been greatly influenced by the geological and geomorphological processes active in the Indian subcontinent.

PHYSIOGRAPHY ‘Physiography’ of an area is the outcome of structure, process and the stage of development. The land of India is characterised by great diversity in its physical features. The north has a vast expanse of rugged topography consisting of a series of mountain ranges with varied peaks, beautiful valleys and deep gorges. The south consists of stable table land with highly dissected plateaus, denuded rocks and developed series of scarps. In between these two lies the vast north Indian plain. Based on these macro variations, India can be divided into the following physiographic divisions: (i) (ii) (iii) (iv) (v) (vi)

Figure 2.1 : A Gorge

INDO-GANGA-BRAHMAPUTRA PLAIN The third geological division of India comprises the plains formed by the river Indus, the Ganga and the Brahmaputra. Originally, it was a geo-synclinal depression which attained its maximum development

The Northern and Northeastern Mountains The Northern Plain The Peninsular Plateau The Indian Desert The Coastal Plains The Islands.

The North and Northeastern Mountains The North and Northeastern Mountains consist of the Himalayas and the Northeastern hills. The Himalayas consist of a series of parallel mountain ranges. Some of the important ranges are the Greater Himalayan range, which includes the Great Himalayas and the TransHimalayan range, the Middle Himalayas and

10

INDIA : PHYSICAL ENVIRONMENT

Figure 2.2 : India : Physical

11

STRUCTURE AND PHYSIOGRAPHY

the Shiwalik. The general orientation of these ranges is from northwest to the southeast direction in the northwestern part of India. Himalayas in the Darjiling and Sikkim regions lie in an eastwest direction, while in Arunachal Pradesh they are from southwest to the northwest direction. In Nagaland, Manipur and Mizoram, they are in the northsouth direction. The approximate length of the Great Himalayan range, also known as the central axial range, is 2,500 km from east to west, and their width varies between 160-400 km from north to south. It is also evident from the map that the Himalayas stand almost like a strong and long wall between the Indian subcontinent and the Central and East Asian countries.

Figure 2.3 : The Himalayas

Himalayas are not only the physical barrier, they are also a climatic, drainage and cultural divide. Can you identify the impact of Himalayas on the geoenvironment of the countries of South Asia? Can you find some other examples of similar geoenvironmental divide in the world? There are large-scale regional variations within the Himalayas. On the basis of relief, alignment of ranges and other geomorphological features, the Himalayas can be divided into the following sub-divisions: (i) (ii) (iii) (iv) (v)

the Great Himalayas and the Pir Panjal range, lies the world famous valley of Kashmir and the famous Dal Lake. Important glaciers of South Asia such as the Baltoro and Siachen are also found in this region. The Kashmir Himalayas are also famous for Karewa Karewas formations, which are useful Karewas are the for the cultivation of Zafran, thick deposits of a local variety of saffron. glacial clay and Some of the important other materials passes of the region are Zoji embedded with La on the Great Himalayas, moraines. Banihal on the Pir Panjal, Photu La on the Zaskar and Khardung La on the Ladakh range. Some of the important fresh lakes such as Dal and Wular and salt water lakes such as Pangong Tso and Tso Moriri are also in this region. This region is drained by the river Indus, and its tributaries such as the Jhelum and the Chenab. The Kashmir and northwestern Himalayas are well-known for their scenic beauty and picturesque landscape. The landscape of Himalayas is a major source of attraction for adventure tourists. Do you know that some famous places of pilgrimage such as Vaishno Devi, Amarnath Cave, Charar -e-Sharif, etc. are also located here and large number of pilgrims visit these places every year? Srinagar, capital city of the state of Jammu and Kashmir is located on the banks of Jhelum river. Dal Lake in Srinagar presents an interesting physical feature. Jhelum in the valley of Kashmir is still in its youth stage and yet forms meanders – a typical feature associated with the mature stage in the evolution of fluvial land form (Figure 2.4). Can you name some other fluvial landforms in the mature stage of a river?

Kashmir or Northwestern Himalayas Himachal and Uttaranchal Himalayas Darjiling and Sikkim Himalayas Arunachal Himalayas Eastern Hills and Mountains.

Kashmir or Northwestern Himalayas It comprise a series of ranges such as the Karakoram, Ladakh, Zaskar and Pir Panjal. The northeastern part of the Kashmir Himalayas is a cold desert, which lies between the Greater Himalayas and the Karakoram ranges. Between

Figure 2.4 : Meandering Jhelum

12

INDIA : PHYSICAL ENVIRONMENT

Figure 2.5 : Western Himalayas

An Interesting Fact In Kashmir Valley, the meanders in Jhelum river are caused by the local base level provided by the erstwhile larger lake of which the present Dal Lake is a small part.

The southernmost part of this region consists of longitudinal valleys known as ‘duns’. Jammu dun and Pathankot dun are important examples. The Himachal and Uttaranchal Himalayas This part lies approximately between the Ravi in the west and the Kali (a tributary of Ghaghara) in the east. It is drained by two major river systems of India, i.e. the Indus and the Ganga. Tributaries of the Indus include the river Ravi, the Beas and the Satluj, and the tributaries of Ganga flowing through this region include the Yamuna and the Ghaghara. The northernmost part of the Himachal Himalayas is an extension of the Ladakh cold

desert, which lies in the Spiti subdivision of district Lahul and Spiti. All the three ranges of Himalayas are prominent in this section also. These are the Great Himalayan range, the Lesser Himalayas (which is locally known as Dhaoladhar in Himachal Pradesh and Nagtibha in Uttaranchal) and the Shiwalik range from the North to the South. In this section of Lesser Himalayas, the altitude between 1,000-2,000 m specially attracted to the British colonial administration, and subsequently, some of the important hill stations such as Dharamshala, Mussoorie, Shimla, Kaosani and the cantonment towns and health resorts such as Shimla, Mussoorie, Kasauli, Almora, Lansdowne and Ranikhet, etc. were developed in this region. The two distinguishing features of this region from the point of view of physiography are the ‘Shiwalik’ and ‘Dun formations’. Some important duns located in this region are the

13

STRUCTURE AND PHYSIOGRAPHY

South

North Figure 2.6 : Himalayan Mountain Complex : Cross Sectional View from South to North

The Shiwalik The word shiwalik has its origin in the geological formation found in and around a place called Sivawala near Dehra Dun which was once a headquarter of the Imperial Survey and which subsequently established its permanent headquarters at Dehra Dun.

Chandigarh-Kalka dun, Nalagarh dun, Dehra Dun, Harike dun and the Kota dun, etc. Dehra Dun is the largest of all the duns with an approximate length of 35-45 km and a width of 22-25 km. In the Great Himalayan range, the valleys are mostly inhabited by the Bhotia’s. These are nomadic groups who migrate to ‘Bugyals’ (the summer glasslands in the higher reaches) during summer months and return to the valleys during winters. The famous ‘Valley of flowers’ is also situated in this region. The places of pilgrimage such as the Gangotri, Yamunotri, Kedarnath, Badrinath and Hemkund Sahib are also situated in this part. The region is also known to have five famous Prayags (river confluences) as mentiond in Chapter 3 of this book. Can you name some other famous prayags in other parts of the country? The Darjiling and Sikkim Himalayas They are flanked by Nepal Himalayas in the west and Bhutan Himalayas in the east. It is relatively small but is a most significant part of the Himalayas. Known for its fast-flowing

rivers such as Tista, it is a region of high mountain peaks like Kanchenjunga (Kanchengiri), and deep valleys. The higher reaches of this region are inhabited by Lepcha tribes while the southern part, particularly the Darjiling Himalayas, has a mixed population of Nepalis, Bengalis and tribals from Central India. The British, taking advantage of the physical conditions such as moderate slope, thick soil cover with high organic content, well distributed rainfall throughout the year and mild winters, introduced tea plantations in this region. As compared to the other sections of the Himalayas, these along with the Arunachal Himalayas are conspicuous by the absence of the Shiwalik formations. In place of the Shiwaliks here, the ‘duar formations’ are important, which have also been used for the development of tea gardens. Sikkim and Darjiling Himalayas are also known for their scenic beauty and rich flora and fauna, particularly various types of orchids. The Arunachal Himalayas These extend from the east of the Bhutan Himalayas up to the Diphu pass in the east. The general direction of the mountain range is from southwest to northeast. Some of the important mountain peaks of the region are Kangtu and Namcha Barwa. These ranges are dissected by fast-flowing rivers from the north to the south, forming deep gorges. Bhramaputra flows through a deep gorge after crossing Namcha Barwa. Some of the important rivers are the Kameng, the

14

INDIA : PHYSICAL ENVIRONMENT

Subansiri, the Dihang, the Dibang and the Lohit. These are perennial with the high rate of fall, thus, having the highest hydro-electric power potential in the country. An important aspect of the Arunachal Himalayas is the numerous ethnic tribal community inhabiting in these areas. Some of the prominent ones from west to east are the Monpa, Daffla, Abor, Mishmi, Nishi and the Nagas. Most of these communities practise Jhumming. It is also known as shifting or slash and burn cultivation. This region is rich in biodiversity which has been preserved by the indigenous

communities. Due to rugged topography, the inter -valley transportation linkages are nominal. Hence, most of the interactions are carried through the duar region along the Arunachal-Assam border. The Eastern Hills and Mountains These are part of the Himalayan mountain system having their general alignment from the north to the south direction. They are known by different local names. In the north, they are known as Patkai Bum, Naga hills, the Manipur

Figure 2.7 : Eastern Himalayas

15

STRUCTURE AND PHYSIOGRAPHY

hills and in the south as Mizo or Lushai hills. These are low hills, inhabited by numerous tribal groups practising Jhum cultivation.

Figure 2.8 : Mizo Hills

Most of these ranges are separated from each other by numerous small rivers. The Barak is an important river in Manipur and Mizoram. The physiography of Manipur is unique by the presence of a large lake known as ‘Loktak’ lake at the centre, surrounded by mountains from all sides. Mizoram which is also known as the ‘Molassis basin’ which is made up of soft unconsolidated deposits. Most of the rivers in Nagaland form the tributary of the Brahmaputra. While two rivers of Mizoram and Manipur are the tributaries of the Barak river, which in turn is the tributary of Meghna; the rivers in the eastern part of Manipur are the tributaries of Chindwin, which in turn is a tributary of the Irrawady of Myanmar.

Figure 2.9 : Loktak Lake

The Northern Plains The northern plains are formed by the alluvial deposits brought by the rivers – the Indus, the Ganga and the Brahmaputra. These plains extend approximately 3,200 km from the east to the west. The average width of these plains varies between 150-300 km. The maximum depth of alluvium deposits varies between 1,000-2,000 m. From the north to the south, these can be divided into three major zones: the Bhabar, the Tarai and the alluvial plains. The alluvial plains can be further divided into the Khadar and the Bhangar. Bhabar is a narrow belt ranging between 8-10 km parallel to the Shiwalik foothills at the break-up of the slope. As a result of this, the streams and rivers coming from the mountains deposit heavy materials of rocks and boulders, and at times, disappear in this zone. South of the Bhabar is the Tarai belt, with an approximate width of 10-20 km where most of the streams and rivers re-emerge without having any properly demarcated channel, thereby, creating marshy and swampy conditions known as the Tarai. This has a luxurious growth of natural vegetation and houses a varied wild life. The south of Tarai is a belt consisting of old and new alluvial deposits known as the Bhangar and Khadar respectively. These plains have characteristic features of mature stage of fluvial erosional and depositional landforms such as sand bars, meanders, oxbow lakes and braided channels. The Brahmaputra plains are known for their riverine islands and sand bars. Most of these areas are subjected to periodic floods and shifting river courses forming braided streams. The mouths of these mighty rivers also form some of the largest deltas of the world, for example, the famous Sunderbans delta. Otherwise, this is a featureless plain with a general elevation of 50-150 m above the mean sea level. The states of Haryana and Delhi form a water divide between the Indus and the Ganga river systems. As opposed to this, the Brahmaputra river flows from the northeast to the southwest direction before it takes an

16

INDIA : PHYSICAL ENVIRONMENT

Figure 2.10 : Northern Plain

almost 90° southward turn at Dhubri before it enters into Bangladesh. These river valley plains have a fertile alluvial soil cover which supports a variety of crops like wheat, rice, sugarcane and jute, and hence, supports a large population. The Peninsular Plateau Rising from the height of 150 m above the river plains up to an elevation of 600-900 m is the irregular triangle known as the Peninsular plateau. Delhi ridge in the northwest, (extension of Aravalis), the Rajmahal hills in the east, Gir range in the west and the Cardamom hills in the south constitute the outer extent of the Peninsular plateau. However, an extension of this is also seen in the northeast, in the form of Shillong and Karbi-Anglong plateau. The Peninsular India is made up of a series of patland plateaus such as the Hazaribagh plateau, the Palamu plateau, the Ranchi plateau, the Malwa plateau, the Coimbatore

plateau and the Karnataka plateau, etc. This is one of the oldest and the most stable landmass of India. The general elevation of the plateau is from the west to the east, which is also proved by the pattern of the flow of rivers. Name some rivers of the Peninsular plateau which have their confluence in the Bay of Bengal and the Arabian sea and mention some landforms which are typical to the east flowing rivers but are absent in the west flowing rivers. Some of the important physiographic features of this region are tors, block mountains, rift valleys, spurs, bare rocky structures, series of hummocky hills and wall-like quartzite dykes offering natural sites for water storage. The western and northwestern part of the plateau has an emphatic presence of black soil. This Peninsular plateau has undergone recurrent phases of upliftment and submergence accompanied by crustal faulting and fractures. (The Bhima fault needs special mention, because of its recurrent seismic activities). These spatial variations have brought in elements of diversity in the relief of the Peninsular plateau. The northwestern part of the plateau has a complex relief of ravines and gorges. The ravines of Chambal, Bhind and Morena are some of the well-known examples. On the basis of the prominent relief features, the Peninsular plateau can be divided into three broad groups: (i) The Deccan Plateau (ii) The Central Highlands (iii) The Northeastern Plateau. The Deccan Plateau

Figure 2.11 : A Part of Peninsular Plateau

This is bordered by the Western Ghats in the west, Eastern Ghats in the east and the Satpura, Maikal range and Mahadeo hills in the north. Western Ghats are locally known by different names such as Sahyadri in Maharashtra, Nilgiri hills in Karnataka and Tamil Nadu and Anaimalai hills and Cardamom hills in Kerala. Western Ghats are comparatively higher in elevation and more continuous than the Eastern Ghats. Their average elevation is about 1,500 m with the height increasing from north to south. ‘Anaimudi’ (2,695 m), the highest peak of

17

STRUCTURE AND PHYSIOGRAPHY

Peninsular plateau is located on the Anaimalai hills of the Western Ghats followed by Dodabetta (2,637 m) on the Nilgiri hills. Most of the Peninsular rivers have their origin in the Western Ghats. Eastern Ghats comprising the discontinuous and low hills are highly eroded by the rivers such as the Mahanadi, the Godavari, the Krishna, the Kaveri, etc. Some of the important ranges include the Javadi hills, the Palconda range, the Nallamala hills, the Mahendragiri hills, etc. The Eastern and the Western Ghats meet each other at the Nilgiri hills. The Central Highlands They are bounded to the west by the Aravali range. The Satpura range is formed by a series of scarped plateaus on the south, generally at an elevation varying between 600-900 m above the mean sea level. This forms the northernmost boundary of the Deccan plateau. It is a classic example of the relict mountains which are highly denuded and form discontinuous ranges. The extension of the Peninsular plateau can be seen as far as Jaisalmer in the West, where it has been covered by the longitudinal sand ridges and crescent-shaped sand dunes called barchans. This region has undergone metamorphic processes in its geological history, which can be corroborated by the presence of metamorphic rocks such as marble, slate, gneiss, etc. The general elevation of the Central Highlands ranges between 700-1,000 m above the mean sea level and it slopes towards the north and northeastern directions. Most of the tributaries of the river Yamuna have their origin in the Vindhyan and Kaimur ranges. Banas is the only significant tributary of the river Chambal that originates from the Aravalli in the west. An eastern extension of the Central Highland is formed by the Rajmahal hills, to the south of which lies a large reserve of mineral resources in the Chotanagpur plateau.

exerted by the northeastward movement of the Indian plate at the time of the Himalayan origin, a huge fault was created between the Rajmahal hills and the Meghalaya plateau. Later, this depression got filled up by the deposition activity of the numerous rivers. Today, the Meghalaya and Karbi Anglong plateau stand detached from the main Peninsular Block. The Meghalaya plateau is further sub-divided into three: (i) The Garo Hills; (ii) The Khasi Hills; (iii) The Jaintia Hills, named after the tribal groups inhabiting this region. An extension of this is also seen in the Karbi Anglong hills of Assam. Similar to the Chotanagpur plateau, the Meghalaya plateau is also rich in mineral resources like coal, iron ore, sillimanite, limestone and uranium. This area receives maximum rainfall from the south west monsoon. As a result, the Meghalaya plateau has a highly eroded surface. Cherrapunji displays a bare rocky surface devoid of any permanent vegetation cover. The Indian Desert To the northwest of the Aravali hills lies the Great Indian desert. It is a land of undulating topography dotted with longitudinal dunes and barchans. This region receives low rainfall below 150 mm per year; hence, it has arid climate with low vegetation cover. It is because of these characteristic features that this is also known as Marusthali. It is believed that

Figure 2.12 : The Indian Desert

The Northeastern Plateau In fact it is an extension of the main Peninsular plateau. It is believed that due to the force

Can you identify the type of sand dunes shown in this picture?

18

during the Mesozoic era, this region was under the sea. This can be corroborated by the evidence available at wood fossils park at Aakal and marine deposits around Brahmsar, near Jaisalmer (The approximate age of the woodfossils is estimated to be 180 million years). Though the underlying rock structure of the desert is an extension of the Peninsular plateau, yet, due to extreme arid conditions, its surface features have been carved by physical weathering and wind actions. Some of the well pronounced desert land features present here are mushroom rocks, shifting dunes and oasis (mostly in its southern part). On the basis of the orientation, the desert can be divided into two parts: the northern part is sloping towards Sindh and the southern towards the Rann of Kachchh. Most of the rivers in this region are ephemeral. The Luni river flowing in the southern part of the desert is of some significance. Low precipitation and high evaporation makes it a water deficit region. There are some streams which disappear after flowing for some distance and present a typical case of inland drainage by joining a lake or playa. The lakes and the playas have brackish water which is the main source of obtaining salt. The Coastal Plains You have already read that India has a long coastline . On the basis of the location and active geomorphological processes, it can be broadly divided into two: (i) the western coastal plains; (ii) the eastern coastal plains. The western coastal plains are an example of submerged coastal plain. It is believed that the city of Dwaraka which was once a part of the Indian mainland situated along the west coast is submerged under water. Because of this submergence it is a narrow belt and provides natural conditions for the development of ports and harbours. Kandla, Mazagaon, JLN port Navha Sheva, Marmagao, Mangalore, Cochin, etc. are some of the important natural ports located along the west coast. Extending from the Gujarat coast in the north to the Kerala coast in the south, the western coast may be divided into following divisions – the Kachchh and

INDIA : PHYSICAL ENVIRONMENT

Figure 2.13 : Coastal Plains

Kathiawar coast in Gujarat, Konkan coast in Maharashtra, Goan coast and Malabar coast in Karnataka and Kerala respectively. The western coastal plains are narrow in the middle and get broader towards north and south. The rivers flowing through this coastal plain do not form any delta. The Malabar coast has got certain distinguishing features in the form of ‘Kayals’ (backwaters), which are used for fishing, inland navigation and also due to its special attraction for tourists. Every year the famous Nehru Trophy Vallamkali (boat race) is held in Punnamada Kayal in Kerala. As compared to the western coastal plain, the eastern coastal plain is broader and is an example of an emergent coast. There are welldeveloped deltas here, formed by the rivers flowing eastward in to the Bay of Bengal. These include the deltas of the Mahanadi, the Godavari, the Krishna and the Kaveri. Because of its emergent nature, it has less number of ports and harbours. The continental shelf extends up to 500 km into the sea, which makes it difficult for the development of good ports and harbours. Name some ports on the eastern coast. The Islands There are two major island groups in India – one in the Bay of Bengal and the other in the Arabian Sea. The Bay of Bengal island groups consist of about 572 islands/islets. These are situated roughly between 6°N-14°N and 92°E -94°E. The two principal groups of islets include the Ritchie’s archipelago and the Labrynth island. The entire group of island is

19

STRUCTURE AND PHYSIOGRAPHY

On 26 December 2004, the Andaman and Nicobar islands experienced one of the most devasting natural calamity. Can you name the calamity and identify some other areas which were adversely affected by the same calamity? What was its major consequence?

divided into two broad categories – the Andaman in the north and the Nicobar in the south. They are separated by a water body which is called the Ten degree channel. It is believed that these islands are an elevated portion of submarine mountains. However, some smaller islands are volcanic in origin. Barren island, the only active volcano in India is also situated in the Nicobar islands. Some important mountain peaks in Andaman and Nicobar islands are Saddle peak (North Andaman – 738 m), Mount Diavolo (Middle Andaman – 515 m), Mount Koyob (South Andaman – 460 m) and Mount Thuiller (Great Nicobar – 642 m).

280 km-480 km off the Kerala coast. The entire island group is built of coral deposits. There are approximately 36 islands of which 11 are inhabited. Minicoy is the largest island with an area of 453 sq. km. The entire group of islands is broadly divided by the Eleventh degree channel, north of which is the Amini Island and to the south of the Canannore Island. The Islands of this archipelago have storm beaches consisting of unconsolidated pebbles, shingles, cobbles and boulders on the eastern seaboard.

The coastal line has some coral deposits, and beautiful beaches. These islands receive convectional rainfall and have an equatorial type of vegetation. The islands of the Arabian sea include Lakshadweep and Minicoy. These are scattered between 8°N-12°N and 71°E -74°E longitude. These islands are located at a distance of

Figure 2.14 : An Island

EXERCISES 1. Choose the right answer from the four alternatives given below. (i) In which part of Himalayas do we find the Karewa formation? (a) North-eastern Himalayas (c) Eastern Himalayas (b) Himachal-Uttaranchal Himalayas (d) Kashmir Himalayas (ii) In which of the following states is Loktak lake situated? (a) Kerala (c) Manipur (b) Uttaranchal (d) Rajasthan (iii) Which one of the water bodies separates the Andaman from the Nicobar? (a) 11° Channel (c) 10° Channel (b) Gulf of Mannar (d) Andaman Sea (iv) On which of the following hill range is the ‘Dodabeta’ peak situated? (a) Nilgiri hills (c) Cardamom hills (b) Anaimalai hills (d) Nallamala hills 2. Answer the following questions in about 30 words. (i) If a person is to travel to Lakshadweep, from which coastal plain does he prefer and why?

20

INDIA : PHYSICAL ENVIRONMENT

(ii) Where in India will you find a cold desert? Name some important ranges of this region. (iii) Why is the western coastal plain is devoid of any delta? 3. Answer the following questions in not more than 125 words. (i) Make a comparison of the island groups of the Arabian Sea and the Bay of Bengal. (ii) What are the important geomorphological features found in the river valley plains? (iii) If you move from Badrinath to Sunderbans delta along the course of the river Ganga, what major geomorphological features will you come across? Project/Activity (i) Make a list of major Himalayan peaks from the west to the east with the help of an atlas. (ii) Identify the major landforms of your state and analyse the major economic activity practised by the people in each landform.

CHAPTER

DRAINAGE SYSTEM

Y

ou have observed water flowing through the rivers, nalas and even channels during rainy season which drain the excess water. Had these channels not been there, large-scale flooding would have occurred. Wherever channels are ill-defined or choked, flooding is a common phenomenon.

2006) in this class . Can you, then, explain the reason for water flowing from one direction to the other? Why do the rivers originating from the Himalayas in the northern India and the Western Ghat in the southern India flow towards the east and discharge their waters in the Bay of Bengal?

The flow of water through well-defined channels is known as ‘drainage’ and the network of such channels is called a ‘drainage system’. The drainage pattern of an area is the outcome of the geological time period, nature and structure of rocks, topography, slope, amount of water flowing and the periodicity of the flow.

Do you have a river near your village or city? Have you ever been there for boating or bathing? Is it perennial (always with water) or ephemeral (water during rainy season, and dry, otherwise)? Do you know that rivers flow in the same direction? You have studied about slopes in the other two textbooks of geography (NCERT,

Figure 3.1 : A River in the Mountainous Region

A river drains the water collected from a specific area, which is called its ‘catchment area’. An area drained by a river and its tributaries is called a drainage basin. The boundary line

Important Drainage Patterns (i) The drainage pattern resembling the branches of a tree is known as “dendritic” the examples of which are the rivers of northern plain. (ii) When the rivers originate from a hill and flow in all directions, the drainage pattern is known as ‘radial’. The rivers originating from the Amarkantak range present a good example of it. (iii) When the primary tributaries of rivers flow parallel to each other and secondary tributaries join them at right angles, the pattern is known as ‘trellis’. (iv) When the rivers discharge their waters from all directions in a lake or depression, the pattern is know as ‘centripetal’. Find out some of the patterns in the topo sheet given in Chapter 5 of Practical Work in Geography– Part I (NCERT, 2006).

22

INDIA : PHYSICAL ENVIRONMENT

Figure 3.2 : Major Rivers of India

23

DRAINAGE SYSTEM

separating one drainage basin from the other is known as the watershed. The catchments of large rivers are called river basins while those of small rivulets and rills are often referred to as watersheds. There is, however, a slight difference between a river basin and a watershed. Watersheds are small in area while the basins cover larger areas. River basins and watersheds are marked by unity. What happens in one part of the basin or watershed directly affects the other parts and the unit as a whole. That is why, they are accepted as the most appropriate micro, meso or macro planning regions. Indian drainage system may be divided on various bases. On the basis of discharge of water (orientations to the sea), it may be grouped into: (i) the Arabian Sea drainage; and (ii) the Bay of Bengal drainage. They are separated from each other through the Delhi ridge, the Aravalis and the Sahyadris (water divide is shown by a line in Figure 3.1). Nearly 77 per cent of the drainage area consisting of the Ganga, the Brahmaputra, the Mahanadi, the Krishna, etc. is oriented towards the Bay of Bengal while 23 per cent comprising the Indus, the Narmada, the Tapi, the Mahi and the Periyar systems discharge their waters in the Arabian Sea. On the basis of the size of the watershed, the drainage basins of India are grouped into three categories: (i) Major river basins with more than 20,000 sq. km of catchment area. It includes 14 drainage basins such as the Ganga, the Brahmaputra, the Krishna, the Tapi, the Narmada, the Mahi, the Pennar, the Sabarmati, the Barak, etc. (Appendix III). (ii) Medium river basins with catchment area between 2,000-20,000 sq. km incorporating 44 river basins such as the Kalindi, the Periyar, the Meghna, etc. (iii) Minor river basins with catchment area of less than 2,000 sq. km include fairly good number of rivers flowing in the area of low rainfall. If you look at the Figure 3.1 you can see that many rivers have their sources in the Himalayas and discharge their waters either in the Bay of Bengal or in the Arabian Sea. Identify these rivers of North India. Large rivers flowing on the Peninsular plateau have their origin in the Western Ghats and discharge their waters

in the Bay of Bengal. Identify these rivers of the South India. The Narmada and Tapi are two large rivers which are exceptions. They along with many small rivers discharge their waters in the Arabian Sea. Name these rivers of the western coastal region from the Konkan to the Malabar coast. On the basis of the mode of origin, nature and characteristics, the Indian drainage may also be classified into the Himalayan drainage and the Peninsular drainage. Although it has the problem of including the Chambal, the Betwa, the Son, etc. which are much older in age and origin than other rivers that have their origin in the Himalayas, it is the most accepted basis of classification. Hence, this scheme has been followed in this book.

DRAINAGE SYSTEMS

OF

INDIA

Indian drainage system consists of a large number of small and big rivers. It is the outcome of the evolutionary process of the three major physiographic units and the nature and characteristics of precipitation.

THE HIMALAYAN DRAINAGE The Himalayan drainage system has evolved through a long geological history. It mainly includes the Ganga, the Indus and the Brahmaputra river basins. Since these are fed both by melting of snow and precipitation, rivers of this system are perennial. These rivers pass through the giant gorges carved out by the erosional activity carried on simultaneously with the uplift of the Himalayas. Besides deep gorges, these rivers also form V-shaped valleys, rapids and waterfalls in their mountainous

Figure 3.3 : Rapids

24

INDIA : PHYSICAL ENVIRONMENT

course. While entering the plains, they form depositional features like flat valleys, ox-bow lakes, flood plains, braided channels, and deltas near the river mouth. In the Himalayan reaches, the course of these rivers is highly tortous, but over the plains they display a strong meandering tendency and shift their courses frequently. River Kosi, also know as the ‘sorrow of Bihar’, has been notorious for frequently changing its course. The Kosi brings huge quantity of sediments from its upper reaches and deposits it in the plains. The course gets blocked, and consequently, the river changes its course. Why does the Kosi river bring such huge quantity of sediments from the upper reaches? Do you think that the discharge of the water in the rivers in general and the Kosi in particular, remains the same, or does it fluctuate? When does the river course receive the maximum quantity of water? What are the positive and negative effects of flooding?

EVOLUTION

OF THE

HIMALAYAN DRAINAGE

There are difference of opinion about the evolution of the Himalayan rivers. However, geologists believe that a mighty river called Shiwalik or Indo-Brahma traversed the entire longitudinal extent of the Himalaya from Assam to Punjab and onwards to Sind, and finally discharged into the Gulf of Sind near lower Punjab during the Miocene period some 5-24 million years ago (See the table of geological times scale in Chapter 2 of Fundamentals of Physical Geography, NCER T, 2006). The remarkable continuity of the Shiwalik and its lacustrine origin and alluvial deposits consisting of sands, silt, clay, boulders and conglomerates support this viewpoint. It is opined that in due course of time Indo– Brahma river was dismembered into three main drainage systems: (i) the Indus and its five tributaries in the western part; (ii) the Ganga and its Himalayan tributaries in the central part; and (iii) the stretch of the Brahmaputra in Assam and its Himalayan tributaries in the eastern part. The dismemberment was probably due to the Pleistocene upheaval in the western Himalayas, including the uplift of

the Potwar Plateau (Delhi Ridge), which acted as the water divide between the Indus and Ganga drainage systems. Likewise, the downthrusting of the Malda gap area between the Rajmahal hills and the Meghalaya plateau during the mid-pleistocene period, diverted the Ganga and the Brahmaputra systems to flow towards the Bay of Bengal.

THE RIVER SYSTEMS OF HIMALAYAN DRAINAGE

THE

The Himalayan drainage consists of several river systems but the following are the major river systems: The Indus System It is one of the largest river basins of the world, covering an area of 11,65,000 sq. km (in India it is 321, 289 sq. km and a total length of 2,880 km (in India 1,114 km). The Indus also known as the Sindhu, is the westernmost of the Himalayan rivers in India. It originates from a glacier near Bokhar Chu (31°15' N latitude and 81°40' E longitude) in the Tibetan region at an altitude of 4,164 m in the Kailash Mountain range. In Tibet, it is known as ‘Singi Khamban; or Lion’s mouth. After flowing in the northwest direction between the Ladakh and Zaskar ranges, it passes through Ladakh and Baltistan. It cuts across the Ladakh range, forming a spectacular gorge near Gilgit in Jammu and Kashmir. It enters into Pakistan near Chillar in the Dardistan region. Find out the area known as Dardistan. The Indus receives a number of Himalayan tributaries such as the Shyok, the Gilgit, the Zaskar, the Hunza, the Nubra, the Shigar, the Gasting and the Dras. It finally emerges out of the hills near Attock where it receives the Kabul river on its right bank. The other important tributaries joining the right bank of the Indus are the Khurram, the Tochi, the Gomal, the Viboa and the Sangar. They all originate in the Sulaiman ranges. The river flows southward and receives ‘Panjnad’ a little above Mithankot. The Panjnad is the name given to the five rivers of Punjab, namely the Satluj, the Beas, the Ravi, the Chenab and the Jhelum. It finally discharges

25

DRAINAGE SYSTEM

into the Arabian Sea, east of Karachi. The Indus flows in India only through the Leh district in Jammu and Kashmir. The Jhelum, an important tributary of the Indus, rises from a spring at Verinag situated at the foot of the Pir Panjal in the south-eastern part of the valley of Kashmir. It flows through Srinagar and the Wular lake before entering Pakistan through a deep narrow gorge. It joins the Chenab near Jhang in Pakistan. The Chenab is the largest tributary of the Indus. It is formed by two streams, the Chandra and the Bhaga, which join at Tandi near Keylong in Himachal Pradesh. Hence, it is also known as Chandrabhaga. The river flows for 1,180 km before entering into Pakistan. The Ravi is another important tributary of the Indus. It rises west of the Rohtang pass in the Kullu hills of Himachal Pradesh and flows through the Chamba valley of the state. Before entering Pakistan and joining the Chenab near Sarai Sidhu, it drains the area lying between the southeastern part of the Pir Panjal and the Dhauladhar ranges. The Beas is another important tributary of the Indus, originating from the Beas Kund near the Rohtang Pass at an elevation of 4,000 m above the mean sea level. The river flows through the Kullu valley and forms gorges at Kati and Largi in the Dhaoladhar range. It enters the Punjab plains where it meets the Satluj near Harike. The Satluj originates in the Rakas lake near Mansarovar at an altitude of 4,555 m in Tibet where it is known as Langchen Khambab. It flows almost parallel to the Indus for about 400 km before entering India, and comes out of a gorge at Rupar. It passes through the Shipki La on the Himalayan ranges and enters the Punjab plains. It is an antecedent river. It is a very important tributary as it feeds the canal system of the Bhakra Nangal project. The Ganga System The Ganga is the most important river of India both from the point of view of its basin and cultural significance. It rises in the Gangotri glacier near Gaumukh (3,900 m) in the

Uttarkashi district of Uttaranchal. Here, it is known as the Bhagirathi. It cuts through the Central and the Lesser Himalayas in narrow gorges. At Devprayag, the Bhagirathi meets the Alaknanda; hereafter, it is known as the Ganga. The Alaknanda has its source in the Satopanth glacier above Badrinath. The Alaknanda consists of the Dhauli and the Vishnu Ganga which meet at Joshimath or Vishnu Prayag. The other tributaries of Alaknanda such as the Pindar join it at Karna Prayag while Mandakini or Kali Ganga meets it at Rudra Prayag. The Ganga enters the plains at Haridwar. From here, it flows first to the south, then to the south-east and east before splitting into two distributaries, namely the Bhagirathi and the Hugli. The river has a length of 2,525 km. It is shared by Uttaranchal (110 km) and Uttar Pradesh (1,450 km), Bihar (445 km) and West Bengal (520 km). The Ganga basin covers about 8.6 lakh sq. km area in India alone. The Ganga river system is the largest in India having a number of perennial and non-perennial rivers originating in the Himalayas in the north and the Peninsula in the south, respectively. The Son is its major right bank tributary. The important left bank tributaries are the Ramganga, the Gomati, the Ghaghara, the Gandak, the Kosi and the Mahanada. The river finally discharges itself into the Bay of Bengal near the Sagar Island. The Yamuna, the western most and the longest tributary of the Ganga, has its source in the Yamunotri glacier on the western slopes of Banderpunch range (6,316 km). It joins the Ganga at Prayag (Allahabad). It is joined by the Chambal, the Sind, the Betwa and the Ken on its right bank which originates from the Peninsular plateau while the Hindan, the Rind, the Sengar, the Varuna, etc. join it on its left bank. Much of its water feeds the western and eastern Yamuna and the Agra canals for irrigation purposes. Name the states which are drained by the river Yamuna.

The Chambal rises near Mhow in the Malwa plateau of Madhya Pradesh and flows northwards through a gorge up wards of Kota

26

in Rajasthan, where the Gandhisagar dam has been constructed. From Kota, it traverses down to Bundi, Sawai Madhopur and Dholpur, and finally joins the Yamuna. The Chambal is famous for its badland topography called the Chambal ravines. The Gandak comprises two streams, namely Kaligandak and Trishulganga. It rises in the Nepal Himalayas between the Dhaulagiri and Mount Everest and drains the central part of Nepal. It enters the Ganga plain in Champaran district of Bihar and joins the Ganga at Sonpur near Patna. The Ghaghara originates in the glaciers of Mapchachungo. After collecting the waters of its tributaries – Tila, Seti and Beri, it comes out of the mountain, cutting a deep gorge at Shishapani. The river Sarda (Kali or Kali Ganga) joins it in the plain before it finally meets the Ganga at Chhapra. The Kosi is an antecedent river with its source to the north of Mount Everest in Tibet, where its main stream Arun rises. After crossing the Central Himalayas in Nepal, it is joined by the Son Kosi from the West and the Tamur Kosi from the east. It forms Sapt Kosi after uniting with the river Arun. The Ramganga is comparatively a small river rising in the Garhwal hills near Gairsain. It changes its course to the southwest direction after crossing the Shiwalik and enters into the plains of Uttar Pradesh near Najibabad. Finally, it joins the Ganga near Kannauj. The Damodar occupies the eastern margins of the Chotanagpur Plateau where it flows through a rift valley and finally joins the Hugli. The Barakar is its main tributary. Once known as the ‘sorrow of Bengal’, the Damodar has been now tamed by the Damodar Valley corporation, a multipurpose project. The Sarda or Saryu river rises in the Milan glacier in the Nepal Himalayas where it is known as the Goriganga. Along the Indo-Nepal border, it is called Kali or Chauk, where it joins the Ghaghara. The Mahananda is another important tributary of the Ganga rising in the Darjiling hills. It joins the Ganga as its last left bank tributary in West Bengal. The Son is a large south bank tributary of

INDIA : PHYSICAL ENVIRONMENT

the Ganga, originating in the Amarkantak plateau. After forming a series of waterfalls at the edge of the plateau, it reaches Arrah, west of Patna, to join the Ganga. The Brahmaputra System The Brahmaputra, one of the largest rivers of the world, has its origin in the Chemayungdung glacier of the Kailash range near the Mansarovar lake. From here, it traverses eastward longitudinally for a distance of nearly 1,200 km in a dry and flat region of southern Tibet, where it is known as the Tsangpo, which means ‘the purifier.’ The Rango Tsangpo is the major right bank tributary of this river in Tibet. It emerges as a turbulent and dynamic river after carving out a deep gorge in the Central Himalayas near Namcha Barwa (7,755 m). The river emerges from the foothills under the name of Siang or Dihang. It enters India west of Sadiya town in Arunachal Pradesh. Flowing southwest, it receives its main left bank tributaries, viz., Dibang or Sikang and Lohit; ther eafter, it is known as the Brahmaputra. The Brahmaputra receives numerous tributaries in its 750 km long journey through the Assam valley. Its major left bank tributaries are the Burhi Dihing, Dhansari (South) and Kalang whereas the important right bank tributaries are the Subansiri, Kameng, Manas and Sankosh. The Subansiri which has its origin in Tibet, is an antecedent river. The Brahmaputra enters into Bangladesh near Dhubri and flows southward. In Bangladesh, the Tista joins it on its right bank from where the river is known as the Yamuna. It finally merges with the river Padma, which falls in the Bay of Bengal. The Brahmaputra is well-known for floods, channel shifting and bank erosion. This is due to the fact that most of its tributaries are large, and bring large quantity of sediments owing to heavy rainfall in its catchment area.

THE PENINSULAR DRAINAGE SYSTEM The Peninsular drainage system is older than the Himalayan one. This is evident from the broad, largely-graded shallow valleys, and the

DRAINAGE SYSTEM

maturity of the rivers. The Western Ghats running close to the western coast act as the water divide between the major Peninsular rivers, discharging their water in the Bay of Bengal and as small rivulets joining the Arabian Sea. Most of the major Peninsular rivers except Narmada and Tapi flow from west to east. The Chambal, the Sind, the Betwa, the Ken, the Son, originating in the northern part of the Peninsula belong to the Ganga river system. The other major river systems of the Peninsular drainage are – the Mahanadi the Godavari, the Krishna and the Kaveri. Peninsular rivers are characterised by fixed course, absence of meanders and nonperennial flow of water. The Narmada and the Tapi which flow through the rift valley are, however, exceptions. The Evolution of Peninsular Drainage System Three major geological events in the distant past have shaped the present drainage systems of Peninsular India: (i) Subsidence of the western flank of the Peninsula leading to its submergence below the sea during the early tertiary period. Generally, it has disturbed the symmetrical plan of the river on either side of the original watershed. (ii) Upheaval of the Himalayas when the northern flank of the Peninsular block was subjected to subsidence and the consequent trough faulting. The Narmada and The Tapi flow in trough faults and fill the original cracks with their detritus materials. Hence, there is a lack of alluvial and deltaic deposits in these rivers. (iii) Slight tilting of the Peninsular block from northwest to the southeastern direction gave orientation to the entire drainage system towards the Bay of Bengal during the same period. River Systems of the Peninsular Drainage There are a large number of river systems in the Peninsular drainage. A brief account of the major Peninsular river systems is given below: The Mahanadi rises near Sihawa in Raipur district of Chhattisgarh and runs through Orissa to discharge its water into the Bay of

27

Bengal. It is 851 km long and its catchment area spreads over 1.42 lakh sq. km. Some navigation is carried on in the lower course of this river. Fifty three per cent of the drainage basin of this river lies in Madhya Pradesh and Chhattisgarh, while 47 per cent lies in Orissa. The Godavari is the largest Peninsular river system. It is also called the Dakshin Ganga. It rises in the Nasik district of Maharashtra and discharges its water into the Bay of Bengal. Its tributaries run through the states of Maharashtra, Madhya Pradesh, Chhattisgarh, Orissa and Andhra Pradesh. It is 1,465 km long with a catchment area spreading over 3.13 lakh sq. km 49 per cent of this, lies in Maharashtra, 20 per cent in Madhya Pradesh and Chhattisgarh, and the rest in Andhra Pradesh. The Penganga, the Indravati, the Pranhita, and the Manjra are its principal tributaries. The Godavari is subjected to heavy floods in its lower reaches to the south of Polavaram, where it forms a picturesque gorge. It is navigable only in the deltaic stretch. The river after Rajamundri splits into several branches forming a large delta. The Krishna is the second largest eastflowing Peninsular river which rises near Mahabaleshwar in Sahyadri. Its total length is 1,401 km. The Koyna, the Tungbhadra and the Bhima are its major tributaries. Of the total catchment area of the Krishna, 27 per cent lies in Maharashtra, 44 per cent in Karnataka and 29 per cent in Andhra Pradesh. The Kaveri rises in Brahmagiri hills (1,341m) of Kogadu district in Karnataka. Its length is 800 km and it drains an area of 81,155 sq. km. Since the upper catchment area receives rainfall during the southwest monsoon season (summer) and the lower part during the northeast monsoon season (winter), the river carries water throughout the year with comparatively less fluctuation than the other Peninsular rivers. About 3 per cent of the Kaveri basin falls in Kerala, 41 per cent in Karnataka and 56 per cent in Tamil Nadu. Its important tributaries are the Kabini, the Bhavani and the Amravati. The Narmada originates on the western flank of the Amarkantak plateau at a height of about 1,057 m. Flowing in a rift valley between the Satpura in the south and the Vindhyan range

28

INDIA : PHYSICAL ENVIRONMENT

in the north, it forms a picturesque gorge in marble rocks and Dhuandhar waterfall near Jabalpur. After flowing a distance of about 1,312 km, it meets the Arabian sea south of Bharuch, forming a broad 27 km long estuary. Its catchment area is about 98,796 sq. km. The Sardar Sarovar Project has been constructed on this river. The Tapi is the other important westward flowing river. It originates from Multai in the Betul district of Madhya Pradesh. It is 724 km long and drains an area of 65,145 sq. km. Nearly 79 per cent of its basin lies in Maharashtra, 15 per cent in Madhya Pradesh and the remaining 6 per cent in Gujarat. Luni is the largest river system of Rajasthan, west of Aravali. It originates near Pushkar in two branches, i.e. the Saraswati and the Sabarmati, which join with each other at Govindgarh. From here, the river comes out of Aravali and is known as Luni. It flows towards the west till Telwara and then takes a southwest direction to join the Rann of Kuchchh. The entire river system is ephemeral. Smaller Rivers Flowing Towards the West The rivers flowing towards the Arabian sea have short courses. Why do they have short courses? Find out the smaller rivers of Gujarat. The Shetruniji is one such river which rises near Dalkahwa in Amreli district. The Bhadra originates near Aniali village in Rajkot district. The Dhadhar rises near Ghantar village in Panchmahal district. Sabarmati and Mahi are the two famous rivers of Gujarat. Find out the places of confluence of these rivers. Find out some important west flowing rivers of Maharashtra.

The Vaitarna rises from the Trimbak hills in Nasik district at an elevation of 670 m. The Kalinadi rises from Belgaum district and falls in the Karwar Bay. The source of Bedti river lies in Hubli Dharwar and traverses a course of 161 km. The Sharavati is another important river in Karnataka flowing towards the west. The Sharavati originates in Shimoga district of Karnataka and drains a catchment area of 2,209 sq. km.

Find out the name of the river on which the Gersoppa (Jog) fall is found.

Goa has two important rivers which can be mentioned here. One is Mandovi and the other is Juari. You can locate them on the map. Kerala has a narrow coastline. The longest river of Kerala, Bharathapuzha rises near Annamalai hills. It is also known as Ponnani. It drains an area of 5,397 sq. km. Compare its catchment area with that of the Sharavati river of Karnataka. The Periyar is the second largest river of Kerala. Its catchment area is 5,243 sq. km. You can see that there is a marginal difference in the catchment area of the Bhartapuzha and the Periyar rivers. Another river of Kerala worth mentioning is the Pamba river which falls in the Vemobanad lake after traversing a course of 177 km. Teachers may explain the comparative importance of west flowing small rivers River Sabarmati Mahi Dhandhar Kalinadi Sharavati Bharathapuzha Periyar

Catchment area sq. km 21,674 34,842 2,770 5,179 2,029 5,397 5,243

Small Rivers Flowing towards the East There are a large number of rivers flowing towards the east along with their tributaries. Can you name some of these rivers? There are small rivers which join the Bay of Bengal, though small, these are important in their own right. The Subarnrekha, the Baitarni, the Brahmani, the Vamsadhara, the Penner, the Palar and the Vaigai are important rivers. Find out these rivers from the atlas. Teachers may explain the comparative importance of east flowing small rivers River Subarnarekha Baitarni Brahmani Penner Palar

Catchment area sq. km 19,296 12,789 39,033 55,213 17,870

29

DRAINAGE SYSTEM

Table 3.1 : Comparison between the Himalayan and the Peninsular River Sl. No.

Aspects

Himalayan River

Peninsular River

1.

Place of origin

Himalayan mountain covered with glaciers

Peninsular plateau and central highland

2.

Nature of flow

Perennial; receive water from glacier and rainfall

Seasonal; dependent on monsoon rainfall

3.

Type of drainage

Antecedent and consequent leading to dendritic pattern in plains

Super imposed, rejuvenated resulting in trellis, radial and rectangular patterns

4.

Nature of river

Long course, flowing through the rugged mountains experiencing headward erosion and river capturing; In plains meandering and shifting of course

Smaller, fixed course with well-adjusted valleys

5.

Catchment area

Very large basins

Relatively smaller basin

6.

Age of the river

Young and youthful, active and deepening in the valleys

Old rivers with graded profile, and have almost reached their base levels

RIVER REGIMES Do you know that the quantity of water flowing in a river channel is not the same throughout the year? It varies from season to season. In which season do you expect the maximum flow in Ganga and Kaveri? The pattern of flow of water in a river channel over a year is known as its regime. The north Indian rivers originating from the Himalayas are perennial as they are fed by glaciers through snow melt and also receive rainfall water during rainy season. The rivers of South India do not originate from glaciers and their flow pattern witnesses fluctuations. The flow increases considerably during monsoon rains. Thus, the regime of the rivers of South India is controlled by rainfall which also varies from one part of the Peninsular plateau to the other. The discharge is the volume of water flowing in a river measured over time. It is measured either in cusecs (cubic feet per second) or cumecs (cubic metres per second). The Ganga has its minimum flow during the January-June period. The maximum flow is attained either in August or in September. After September, there is a steady fall in the flow. The river, thus, has a monsoon regime during the rainy season. There are striking differences in the river regimes in the eastern and the western parts of the Ganga Basin. The Ganga maintains a

sizeable flow in the early part of summer due to snow melt before the monsoon rains begin. The mean maximum discharge of the Ganga at Farakka is about 55,000 cusecs while the mean minimum is only 1,300 cusecs. What factors are responsible for such a large difference? The two Peninsular rivers display interesting differences in their regimes compared to the Himalayan rivers. The Narmada has a very low volume of discharge from January to July but it suddenly rises in August when the maximum flow is attained. The fall in October is as spectacular as the rise in August. The flow of water in the Narmada, as recorded at Garudeshwar, shows that the maximum flow is of the order of 2,300 cusecs, while the minimum flow is only 15 cusecs. The Godavari has the minimum discharge in May, and the maximum in July-August. After August, there is a sharp fall in water flow although the volume of flow in October and November is higher than that in any of the months from January to May. The mean maximum discharge of the Godavari at Polavaram is 3,200 cusecs while the mean minimum flow is only 50 cusecs. These figures give an idea of the regime of the river.

EXTENT

OF

USABILITY

OF

RIVER WATER

The rivers of India carry huge volumes of water

30

INDIA : PHYSICAL ENVIRONMENT

per year but it is unevenly distributed both in time and space. There are perennial rivers carrying water throughout the year while the non-perennial rivers have very little water during the dry season. During the rainy season, much of the water is wasted in floods and flows down to the sea. Similarly, when there is a flood in one part of the country, the other area suffers from drought. Why does this happen? Is it the problem of availability of water resource or that of its management? Can you suggest some measures to mitigate the problems of floods and droughts simultaneously occuring in different parts of the country? (See Chapter 7 of the book). Can these problems be solved or minimised by trasfering the surplus water from one basin to the water deficit basins? Do we have some schemes of inter-basin linkage? Teachers may explain the following examples • Periyar Diversion Scheme • Indira Gandhi Canal Project • Kurnool-Cuddapah Canal • Beas-Satluj Link Canal • Ganga-Kaveri Link Canal

Have you read in the newspapers about the linking of rivers? Do you think that digging a canal is enough to transfer water from the Ganga basin to the Peninsular river? What is the major problem? Consult Chapter 2 of this book and

find out the difficulties posed by the unevenness of the terrain. How can the water be lifted from the plain area to the plateau area? Is there sufficient surplus water in the north Indian rivers which can be transferred on a regular basis? Organise a debate on the whole issue and prepare a write up. How do you rank the following problems in using river water? (i) (ii) (iii) (iv) (v) (vi)

No availability in sufficient quantity River water pollution Load of silt in the river water Uneven seasonal flow of water River water disputes between states Shrinking of channels due to the extension of settlements towards the thalweg.

Why are the rivers polluted? Have you seen the dirty waters of cities entering into the rivers? Where do the industrial affluents and wastes get disposed of ? Most of the cremation grounds are on the banks of rivers and the dead bodies are sometimes thrown in the rivers. On the occasion of some festivals, the flowers and statues are immersed in the rivers. Large scale bathing and washing of clothes also pollute river waters. How can the rivers be made pollution free? Have you read about Ganga Action Plan, or about a campaign for cleaning the Yamuna at Delhi? Collect materials on schemes for making rivers pollution free and organise the materials in a write up.

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i) Which one of the following rivers was known as the ‘Sorrow of Bengal’? (a) The Gandak (c) The Kosi (b) The Son (d) The Damodar (ii) Which one of the following rivers has the largest river basin in India? (a) The Indus (c) The Ganga (b) The Brahmaputra (d) The Krishna (iii) Which one of the following rivers is not included in ‘Panchnad’? (a) The Ravi (c) The Indus (b) The Chenab (d) The Jhelum (iv) Which one of the following rivers flows in a rift valley? (a) The Son (c) The Yamuna (b) The Narmada (d) The Luni

31

DRAINAGE SYSTEM

(v)

Which one of the following is the place of confluence of the Alkananda and the Bhagirathi? (a) Vishnu Prayag (c) Karan Prayag (b) Rudra Prayag (d) Deva Prayag

2.

State the differences between the following. (i) River Basin and Watershed (ii) Dendritic and Trellis drainage pattern (iii) Radial and Centripetal drainage pattern (iv) Delta and Estuary

3.

Answer the following questions in about 30 words. (i) What are the socio-economic advantages of inter-linking of rivers in India? (ii) Write three characterstics of the Peninsular river.

4.

Answer the following questions in not more than 125 words. (i) What are the important characteristic features of north Indian rivers? How are these different from Peninsular rivers? (ii) Suppose you are travelling from Hardwar to Siliguri along the foothills of the Himalayas. Name the important rivers you will come across. Describe the characteristics of any one of them.

Project/Activity Study the Appendix III and answer the following questions. (i) Which river has the largest proportion of catchment area in the country? (ii) Make a comparative bar diagram on a graph paper to show the length of the courses of the rivers.

UNIT III CLIMATE, VEGETATION AND SOIL This unit deals with •

Weather and climate – spatial and temporal distribution of temperature, pressure, winds and rainfall; Indian monsoons: mechanism, onset and variability – spatial and temporal; climatic types

•

Natural vegetation – forest types and distribution; wild life conservation; biosphere reserves

•

Soils – major types and their distribution, soil degradation and conservation

CHAPTER

CLIMATE

W

e drink more water during summers. Your uniform during the summer is different from the winters. Why do you wear lighter clothes during summers and heavy woollen clothes during winters in north India? In southern India, woollen clothes are not required. In northeastern states, winters are mild except in the hills. There are variations in weather conditions during different seasons. These changes occur due to the changes in the elements of weather (temperature, pressure, wind direction and velocity, humidity and precipitation, etc.). Weather is the momentary state of the atmosphere while climate refers to the average of the weather conditions over a longer period of time. Weather changes quickly, may be within a day or week but climate changes imperceptively and may be noted after 50 years or even more.

You have already studied about the monsoon in your earlier classes. You are also aware of the meaning of the word, “monsoon”. Monsoon connotes the climate associated with seasonal reversal in the direction of winds. India has hot monsoonal climate which is the prevalent climate in south and southeast Asia.

UNITY AND DIVERSITY IN THE MONSOON CLIMATE The monsoon regime emphasises the unity of India with the rest of southeast Asian region. This view of broad unity of the monsoon type of climate should not, however, lead one to ignore its regional variations which differentiate

the weather and climate of different regions of India. For example, the climate of Kerala and Tamil Nadu in the south are so different from that of Uttar Pradesh and Bihar in the north, and yet all of these have a monsoon type of climate. The climate of India has many regional variations expressed in the pattern of winds, temperature and rainfall, rhythm of seasons and the degree of wetness or dryness. These regional diversities may be described as sub-types of monsoon climate. Let us take a closer look at these regional variations in temperature, winds and rainfall. While in the summer the mercury occasionally touches 55°C in the western Rajasthan, it drops down to as low as minus 45°C in winter around Leh. Churu in Rajasthan may record a temperature of 50°C or more on a June day while the mercury hardly touches 19°C in Tawang (Arunachal Pradesh) on the same day. On a December night, temperature in Drass (Jammu and Kashmir) may drop down to minus 45°C while Tiruvanantapuram or Chennai on the same night records 20°C or 22°C. These examples confirm that there are seasonal variations in temperature from place to place and from region to region in India. Not only this, if we take only a single place and record the temperature for just one day, variations are no less striking. In Kerala and in the Andaman Islands, the difference between day and night temperatures may be hardly seven or eight degree Celsius. But in the Thar desert, if the day temperature is around 50°C, at night, it may drop down considerably upto 15°-20°C.

34

INDIA : PHYSICAL ENVIRONMENT

Now, let us see the regional variations in precipitation. While snowfall occurs in the Himalayas, it only rains over the rest of the country. Similarly, variations are noticeable not only in the type of precipitation but also in its amount. While Cherrapunji and Mawsynram in the Khasi Hills of Meghalaya receive rainfall over 1,080 cm in a year, Jaisalmer in Rajasthan rarely gets more than 9 cm of rainfall during the same period. Tura situated in the Garo Hills of Meghalaya may receive an amount of rainfall in a single day which is equal to 10 years of rainfall at Jaisalmer. While the annual precipitation is less than 10 cm in the northwest Himalayas and the western deserts, it exceeds 400 cm in Meghalaya. The Ganga delta and the coastal plains of Orissa are hit by strong rain-bearing storms almost every third or fifth day in July and August while the Coromandal coast, a thousand km to the south, goes generally dry during these months. Most parts of the country get rainfall during June-September, but on the coastal areas of Tamil Nadu, it rains in the beginning of the winter season. In spite of these differences and variations, the climate of India is monsoonal in rhythm and character.

FACTORS DETERMINING

THE

CLIMATE

OF

INDIA

India’s climate is controlled by a number of factors which can be broadly divided into two groups — factors related to location and relief, and factors related to air pressure and winds. Factors related to Location and Relief Latitude : You already know the latitudinal and longitudinal extent of the land of India. You also know that the Tropic of Cancer passes through the central part of India in east-west direction. Thus, northern part of the India lies in sub-tropical and temperate zone and the part lying south of the Tropic of Cancer falls in the tropical zone. The tropical zone being nearer to the equator, experiences high temperatures throughout the year with small daily and annual range. Area north of the Tropic of Cancer being away from the equator,

experiences extreme climate with high daily and annual range of temperature. The Himalayan Mountains : The lofty Himalayas in the north along with its extensions act as an effective climatic divide. The towering mountain chain provides an invincible shield to protect the subcontinent from the cold northern winds. These cold and chilly winds originate near the Arctic circle and blow across central and eastern Asia. The Himalayas also trap the monsoon winds, forcing them to shed their moisture within the subcontinent. Distribution of Land and Water : India is flanked by the Indian Ocean on three sides in the south and girdled by a high and continuous mountain-wall in the north. As compared to the landmass, water heats up or cools down slowly. This differential heating of land and sea creates different air pressure zones in different seasons in and around the Indian subcontinent. Difference in air pressure causes reversal in the direction of monsoon winds. Distance from the Sea : With a long coastline, large coastal areas have an equable climate. Areas in the interior of India are far away from the moderating influence of the sea. Such areas have extremes of climate. That is why, the people of Mumbai and the Konkan coast have hardly any idea of extremes of temperature and the seasonal rhythm of weather. On the other hand, the seasonal contrasts in weather at places in the interior of the country such as Delhi, Kanpur and Amritsar affect the entire sphere of life. Altitude : Temperature decreases with height. Due to thin air, places in the mountains are cooler than places on the plains. For example, Agra and Darjiling are located on the same latitude, but temperature of January in Agra is 16°C whereas it is only 4°C in Darjiling. Relief : The physiography or relief of India also affects the temperature, air pressure, direction and speed of wind and the amount and distribution of rainfall. The windward sides of Western Ghats and Assam receive high rainfall

35

CLIMATE

during June-September whereas the southern plateau remains dry due to its leeward situation along the Western Ghats. Factors Related to Air Pressure and Wind To understand the differences in local climates of India, we need to understand the mechanism of the following three factors: (i) Distribution of air pressure and winds on the surface of the earth. (ii) Upper air circulation caused by factors controlling global weather and the inflow of different air masses and jet streams. (iii) Inflow of western cyclones generally known as disturbances during the winter season and tropical depressions during the south-west monsoon period into India, creating weather conditions favourable to rainfall. The mechanism of these three factors can be understood with reference to winter and summer seasons of the year separately.

up in the lower troposphere, about three km above the surface of the earth, a different pattern of air circulation is observed. The variations in the atmospheric pressure closer to the surface of the earth have no role to play in the making of upper air circulation. All of Western and Central Asia remains under the influence of westerly winds along the altitude of 9-13 km from west to east. These winds blow across the Asian continent at latitudes north of the Himalayas roughly parallel to the Tibetan highlands (Figure 4.1). These are known as jet streams. Tibetan highlands act as a barrier in the path of these jet streams. As a result, jet streams get bifurcated. One of its branches blows to the north of the Tibetan highlands, while the southern branch blows in an eastward direction, south of the Himalayas. It has its mean position at 25°N in February at 200-300 mb level. It is believed that this southern branch of the jet stream exercises an important influence on the winter weather in India.

Mechanism of Weather in the Winter Season Surface Pressure and Winds : In winter months, the weather conditions over India are generally influenced by the distribution of pressure in Central and Western Asia. A high pressure centre in the region lying to the north of the Himalayas develops during winter. This centre of high pressure gives rise to the flow of air at the low level from the north towards the Indian subcontinent, south of the mountain range. The surface winds blowing out of the high pressure centre over Central Asia reach India in the form of a dry continental air mass. These continental winds come in contact with trade winds over northwestern India. The position of this contact zone is not, however, stable. Occasionally, it may shift its position as far east as the middle Ganga valley with the result that the whole of the northwestern and northern India up to the middle Ganga valley comes under the influence of dry northwestern winds. Jet Stream and Upper Air Circulation : The pattern of air circulation discussed above is witnessed only at the lower level of the atmosphere near the surface of the earth. Higher

Figure 4.1 : Direction of Winds in India in Winter at the Height of 9-13 km

Western Cyclonic Disturbance and Tropical Cyclones : The western cyclonic disturbances which enter the Indian subcontinent from the west and the northwest during the winter months, originate over the Mediterranean Sea and are

36

INDIA : PHYSICAL ENVIRONMENT

brought into India by the westerly jet stream. An increase in the prevailing night temperature generally indicates an advance in the arrival of these cyclones disturbances. Tropical cyclones originate over the Bay of Bengal and the Indian ocean. These tropical cyclones have very high wind velocity and heavy rainfall and hit the Tamil Nadu, Andhra Pradesh and Orissa coast. Most of these cyclones are very destructive due to high wind velocity and torrential rain that accompanies it. Have you seen their movement in the weather report in the television? Mechanism of Weather in the Summer Season Surface Pressure and Winds : As the summer sets in and the sun shifts northwards, the wind circulation over the subcontinent undergoes a complete reversal at both, the lower as well as the upper levels. By the middle of July, the low pressure belt nearer the surface [termed as Inter Tropical Convergence Zone (ITCZ)]

shifts northwards, roughly parallel to the Himalayas between 20° N and 25° N. By this time, the westerly jet stream withdraws from the Indian region. In fact, meteorologists have found an interrelationship between the northward shift of the equatorial trough (ITCZ) and the withdrawal of the westerly jet stream from over the North Indian Plain. It is generally believed that there is a cause and effect relationship between the two. The ITCZ being a zone of low pressure, attracts inflow of winds from different directions. The maritime tropical airmass (mT) from the southern hemisphere, after crossing the equator, rushes to the low pressure area in the general southwesterly direction. It is this moist air current which is popularly known as the southwest monsoon. Jet Streams and Upper Air Circulation : The pattern of pressure and winds as mentioned above is formed only at the level of the troposphere. An easterly jet stream flows over

Figure 4.2 : Summer Monsoon Winds : Surface Circulation

37

CLIMATE

Inter Tropical Convergence Zone (ITCZ) The Inter Tropical Convergence Zone (ITCZ) is a low pressure zone located at the equator where trade winds converge, and so, it is a zone where air tends to ascend. In July, the ITCZ is located around 20°N-25°N latitudes (over the Gangetic plain), sometimes called the monsoon trough. This monsoon trough encourages the development of thermal low over north and northwest India. Due to the shift of ITCZ, the trade winds of the southern hemisphere cross the equator between 40° and 60°E longitudes and start blowing from southwest to northeast due to the Coriolis force. It becomes southwest monsoon. In winter, the ITCZ moves southward, and so the reversal of winds from northeast to south and southwest, takes place. They are called northeast monsoons.

the southern part of the Peninsula in June, and has a maximum speed of 90 km per hour (Figure 4.3). In August, it is confined to 15oN latitude, and in September up to 22o N latitudes. The easterlies normally do not extend to the north of 30o N latitude in the upper atmosphere.

THE NATURE

OF

INDIAN MONSOON

Monsoon is a familiar though a little known climatic phenomenon. Despite the observations spread over centuries, the monsoon continues to puzzle the scientists. Many attempts have been made to discover the exact nature and causation of monsoon, but so far, no single theory has been able to explain the monsoon fully. A real breakthrough has come recently when it was studied at the global rather than at regional level. Systematic studies of the causes of rainfall in the South Asian region help to understand the causes and salient features of the monsoon, particularly some of its important aspects, such as: (i) The onset of the monsoon. (ii) Rain-bearing systems (e.g. tropical cyclones) and the relationship between their frequency and distribution of monsoon rainfall. (iii) Break in the monsoon. Onset of the Monsoon

Figure 4.3 : The Direction of Winds at 13 km Altitude in Summer Season

Easterly Jet Stream and Tropical Cyclones : The easterly jet stream steers the tropical depressions into India. These depressions play a significant role in the distribution of monsoon rainfall over the Indian subcontinent. The tracks of these depressions are the areas of highest rainfall in India. The frequency at which these depressions visit India, their direction and intensity, all go a long way in determining the rainfall pattern during the southwest monsoon period.

Towards the end of the nineteenth century, it was believed that the differential heating of land and sea during the summer months is the mechanism which sets the stage for the monsoon winds to drift towards the subcontinent. During April and May when the sun shines vertically over the Tropic of Cancer, the large landmass in the north of Indian ocean gets intensely heated. This causes the formation of an intense low pressure in the northwestern part of the subcontinent. Since the pressure in the Indian Ocean in the south of the landmass is high as water gets heated

38

INDIA : PHYSICAL ENVIRONMENT

The shift in the position of the ITCZ is also related to the phenomenon of the withdrawal of the westerly jet stream from its position over the north Indian plain, south of the Himalayas. The easterly jet stream sets in along 15°N latitude only after the western jet stream has withdrawn itself from the region. This easterly jet stream is held responsible for the burst of the monsoon in India. Entry of Monsoon into India : The southwest monsoon sets in over the Kerala coast by 1st June and moves swiftly to reach Mumbai and Kolkata between 10th and 13th June. By midJuly, southwest monsoon engulfs the entire subcontinent (Figure 4.5) Rain-bearing Systems and Rainfall Distribution Figure 4.4 : Onset of Monsoon

slowly, the low pressure cell attracts the southeast trades across the Equator. These conditions help in the northward shift in the position of the ITCZ. The southwest monsoon may thus, be seen as a continuation of the southeast trades deflected towards the Indian subcontinent after crossing the Equator. These winds cross the Equator between 40°E and 60°E longitudes.

There seem to be two rain-bearing systems in India. First originate in the Bay of Bengal causing rainfall over the plains of north India. Second is the Arabian Sea current of the southwest monsoon which brings rain to the west coast of India. Much of the rainfall along the Western Ghats is orographic as the moist air is obstructed and forced to rise along the Ghats. The intensity of rainfall over the west coast of India is, however, related to two factors: (i) The offshore meteorological conditions. (ii) The position of the equatorial jet stream along the eastern coast of Africa.

EI-Nino and the Indian Monsoon EI-Nino is a complex weather system that appears once every three to seven years, bringing drought, floods and other weather extremes to different parts of the world. The system involves oceanic and atmospheric phenomena with the appearance of warm currents off the coast of Peru in the Eastern Pacific and affects weather in many places including India. EI-Nino is merely an extension of the warm equatorial current which gets replaced temporarily by cold Peruvian current or Humbolt current (locate these currents in your atlas). This current increases the temperature of water on the Peruvian coast by 10°C. This results in: (i) the distortion of equatorial atmospheric circulation; (ii) irregularities in the evaporation of sea water; (iii) reduction in the amount of planktons which further reduces the number of fish in the sea. The word EI-Nino means ‘Child Christ’ because this current appears around Christmas in December. December is a summer month in Peru (Southern Hemisphere). EI-Nino is used in India for forecasting long range monsoon rainfall. In 1990-91, there was a wild EI-Nino event and the onset of southwest monsoon was delayed over most parts of the country ranging from five to twelve days.

39

CLIMATE

Figure 4.5 : India : Normal Dates of Onset of the Southwest Monsoon

40

INDIA : PHYSICAL ENVIRONMENT

The frequency of the tropical depressions originating from the Bay of Bengal varies from year to year. Their paths over India are mainly determined by the position of ITCZ which is generally termed as the monsoon trough. As the axis of the monsoon trough oscillates, there are fluctuations in the track and direction of these depressions, and the intensity and the amount of rainfall vary from year to year. The rain which comes in spells, displays a declining trend from west to east over the west coast, and from the southeast towards the northwest over the North Indian Plain and the northern part of the Peninsula. Break in the Monsoon During the south-west monsoon period after having rains for a few days, if rain fails to occur for one or more weeks, it is known as break in the monsoon. These dry spells are quite common during the rainy season. These breaks in the different regions are due to different reasons: (i) In northern India rains are likely to fail if the rain-bearing storms are not very frequent along the monsoon trough or the ITCZ over this region. (ii) Over the west coast the dry spells are associated with days when winds blow parallel to the coast.

THE RHYTHM

OF

may be quite low, sometimes going below freezing point in Punjab and Rajasthan. There are three main reasons for the excessive cold in north India during this season : (i) States like Punjab, Haryana and Rajasthan being far away from the moderating influence of sea experience continental climate. (ii) The snowfall in the nearby Himalayan ranges creates cold wave situation; and (iii) Around February, the cold winds coming from the Caspian Sea and Turkmenistan bring cold wave along with frost and fog over the northwestern parts of India. Understanding the Monsoon Attempts have been made to understand the nature and mechanism of the monsoon on the basis of data collected on land, oceans and in the upper atmosphere. The intensity of southwest monsoon winds of southern oscillation can be measured, among others, by measuring the difference in pressure between Tahiti (roughly 20°S and 140°W) in French Polynesia in East Pacific and port Darwin (12°30'S and 131°E) in northern Australia. Indian Meteorological Department (IMD) can forecast the possible behaviour of monsoons on the basis of 16 indicators.

SEASONS

The Cold Weather Season

The Peninsular region of India, however, does not have any well-defined cold weather season. There is hardly any seasonal change in the distribution pattern of the temperature in coastal areas because of moderating influence of the sea and the proximity to equator. For example, the mean maximum temperature for January at Thiruvanantapuram is as high as 31°C, and for June, it is 29.5°C. Temperatures at the hills of Western Ghats remain comparatively low (Figure 4.6).

Temperature : Usually, the cold weather season sets in by mid-November in northern India. December and January are the coldest months in the northern plain. The mean daily temperature remains below 21°C over most parts of northern India. The night temperature

Pressure and Winds : By the end of December (22nd December), the sun shines vertically over the Tropic of Capricorn in the southern hemisphere. The weather in this season is characterised by feeble high pressure conditions over the northern plain. In south

The climatic conditions of India can best be described in terms of an annual cycle of seasons. The meteorologists recognise the following four seasons : (i) (ii) (iii) (iv)

the cold weather season the hot weather season the southwest monsoon season the retreating monsoon season.

41

CLIMATE

Figure 4.6 : India : Mean Monthly Temperatures of the Day in January

42

India, the air pressure is slightly lower. The isobars of 1019 mb and 1013 mb pass through northwest India and far south, respectively (Figure 4.7). As a result, winds start blowing from northwestern high pressure zone to the low air pressure zone over the Indian Ocean in the south. Due to low pressure gradient, the light winds with a low velocity of about 3-5 km per hour begin to blow outwards. By and large, the topography of the region influences the wind direction. They are westerly or northwesterly down the Ganga Valley. They become northerly in the Ganga-Brahmaputra delta. Free from the influence of topography, they are clearly northeasterly over the Bay of Bengal. During the winters, the weather in India is pleasant. The pleasant weather conditions, however, at intervals, get disturbed by shallow cyclonic depressions originating over the east Mediterranean Sea and travelling eastwards across West Asia, Iran, Afghanistan and Pakistan before they reach the northwestern parts of India. On their way, the moisture content gets augmented from the Caspian Sea in the north and the Persian Gulf in the south. What is the role of Westerly Jet Streams in steering these depressions in India? Rainfall : Winter monsoons do not cause rainfall as they move from land to the sea. It is because firstly, they have little humidity; and secondly, due to anti cyclonic circulation on land, the possibility of rainfall from them reduces. So, most parts of India do not have rainfall in the winter season. However, there are some exceptions to it: (i) In northwestern India, some weak temperate cyclones from the Mediterranean sea cause rainfall in Punjab, Haryana, Delhi and western Uttar Pradesh. Although the amount is meagre, it is highly beneficial for rabi crops. The precipitation is in the form of snowfall in the lower Himalayas. It is this snow that sustains the flow of water in the

INDIA : PHYSICAL ENVIRONMENT

Himalayan rivers during the summer months. The precipitation goes on decreasing from west to east in the plains and from north to south in the mountains. The average winter rainfall in Delhi is around 53 mm. In Punjab and Bihar, rainfall remains between 25 mm and 18 mm respectively. (ii) Central parts of India and northern parts of southern Peninsula also get winter rainfall occasionally. (iii) Arunachal Pradesh and Assam in the northeastern parts of India also have rains between 25 mm and 50 mm during these winter months. (iv) D u r i n g O c t o b e r a n d N o v e m b e r, northeast monsoon while crossing over the Bay of Bengal, picks up moisture and causes torrential rainfall over the Tamil Nadu coast, southern Andhra Pradesh, southeast Karnataka and southeast Kerala. The Hot Weather Season Temperature: With the apparent northward movement of the sun towards the Tropic of Cancer in March, temperatures start rising in north India. April, May and June are the months of summer in north India. In most parts of India, temperatures recorded are between 30°-32°C. In March, the highest day temperature of about 38°C occurs in the Deccan Plateau while in April, temperature ranging between 38°C and 43°C are found in Gujarat and Madhya Pradesh. In May, the heat belt moves further north, and in the north-western part of India, temperatures around 48°C are not uncommon (Figure 4.8). The hot weather season in south India is mild and not so intense as found in north India. The Peninsular situation of south India with moderating effect of the oceans keeps the temperatures lower than that prevailing in north India. So, temperatures remain between 26°C and 32°C. Due to altitude, the temperatures in the hills of Western Ghats remain below 25°C. In the coastal regions, the north-south extent of

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Figure 4.7 : India : Pressure and Surface Winds (January)

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Figure 4.8 : India : Mean Monthly Temperature of the Day in July

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isotherms parallel to the coast confirms that temperature does not decrease from north to south rather it increases from the coast to the interior. The mean daily minimum temperature during the summer months also remains quite high and rarely goes below 26°C. Pressure and Winds : The summer months are a period of excessive heat and falling air pressure in the northern half of the country. Because of the heating of the subcontinent, the ITCZ moves northwards occupying a position centred at 25°N in July. Roughly, this elongated low pressure monsoon trough extends over the Thar desert in the north-west to Patna and Chotanagpur plateau in the east-southeast (Figure 4.9). The location of the ITCZ attracts a surface circulation of the winds which are southwesterly on the west coast as well as a l o n g t h e c o a s t o f We s t B e n g a l a n d Bangladesh. They are easterly or southeasterly over north Bengal and Bihar. It has been discussed earlier that these currents of southwesterly monsoon are in reality ‘displaced’ equatorial westerlies. The influx of these winds by mid-June brings about a change in the weather towards the rainy season. In the heart of the ITCZ in the northwest, the dry and hot winds known as ‘Loo’, blow in the afternoon, and very often, they continue to well into midnight. Dust storms in the evening are very common during May in Punjab, Haryana, Eastern Rajasthan and Uttar Pradesh. These temporary storms bring a welcome respite from the oppressing heat since they bring with them light rains and a pleasant cool breeze. Occasionally, the moisture-laden winds are attracted towards the periphery of the trough. A sudden contact between dry and moist air masses gives rise to local storms of great intensity. These local storms are associated with violent winds, torrential rains and even hailstorms.

Some Famous Local Storms of Hot Weather Season (i) Mango Shower : Towards the end of summer, there are pre-monsoon showers which are a common phenomena in Kerala and coastal areas of Karnataka. Locally, they are known as mango showers since they help in the early ripening of mangoes. (ii) Blossom Shower : With this shower, coffee flowers blossom in Kerala and nearby areas. (iii) Nor Westers : These are dreaded evening thunderstorms in Bengal and Assam. Their notorious nature can be understood from the local nomenclature of ‘Kalbaisakhi’, a calamity of the month of Baisakh. These showers are useful for tea, jute and rice cultivation. In Assam, these storms are known as “Bardoli Chheerha”. (iv) Loo : Hot, dry and oppressing winds blowing in the Northern plains from Punjab to Bihar with higher intensity between Delhi and Patna.

THE SOUTHWEST MONSOON SEASON As a result of rapid increase of temperature in May over the northwestern plains, the low pressure conditions over there get further intensified. By early June, they are powerful enough to attract the trade winds of Southern Hemisphere coming from the Indian Ocean. These southeast trade winds cross the equator and enter the Bay of Bengal and the Arabian Sea, only to be caught up in the air circulation over India. Passing over the equatorial warm currents, they bring with them moisture in abundance. After crossing the equator, they follow a southwesterly direction. That is why they are known as southwest monsoons. The rain in the southwest monsoon season begins rather abruptly. One result of the first rain is that it brings down the temperature substantially. This sudden onset of the moisture-laden winds associated with violent thunder and lightening, is often termed as the “break” or “burst” of the

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Figure 4.9 : India : Pressure and Surface Winds (July)

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monsoons. The monsoon may burst in the first week of June in the coastal areas of Kerala, Karnataka, Goa and Maharashtra while in the interior parts of the country, it may be delayed to the first week of July. The day temperature registers a decline of 5°C to 8°C between midJune and mid-July. As these winds approach the land, their southwesterly direction is modified by the relief and thermal low pressure over the northwest India. The monsoon approaches the landmass in two branches: (i) The Arabian Sea branch (ii) The Bay of Bengal branch. Monsoon Winds of the Arabian Sea The monsoon winds originating over the Arabian Sea further split into three branches: (i) Its one branch is obstructed by the Western Ghats. These winds climb the slopes of the Wester n Ghats from 900-1200 m. Soon, they become cool, and as a result, the windward side of the Sahyadris and Western Coastal Plain receive very heavy rainfall ranging between 250 cm and 400 cm. After crossing the Western Ghats, these winds descend and get heated up. This reduces humidity in the winds. As a result, these winds cause little rainfall east of the Western Ghats. This region of low rainfall is known as the rain-shadow area. Find out the rainfall at Kozhikode, Mangalore, Pune and Bangalore and note the difference (Figure 4.10). (ii) Another branch of the Arabian sea monsoon strikes the coast north of Mumbai. Moving along the Narmada and Tapi river valleys, these winds cause rainfall in extensive areas of central India. The Chotanagpur plateau gets 15 cm rainfall from this part of the branch. Thereafter, they enter the Ganga plains and mingle with the Bay of Bengal branch. (iii) A third branch of this monsoon wind strikes the Saurashtra Peninsula and the Kachchh. It then passes over west Rajasthan and along the Aravallis, causing only a scanty rainfall. In Punjab

and Haryana, it too joins the Bay of Bengal branch. These two branches, reinforced by each other, cause rains in the western Himalayas, Monsoon Winds of the Bay of Bengal The Bay of Bengal branch strikes the coast of Myanmar and part of southeast Bangladesh. But the Arakan Hills along the coast of Myanmar deflect a big portion of this branch towards the Indian subcontinent. The monsoon, therefore, enters West Bengal and Bangladesh from south and southeast instead of from the south-westerly direction. From here, this branch splits into two under the influence of the Himalayas and the thermal low is northwest India. Its one branch moves westward along the Ganga plains reaching as far as the Punjab plains. The other branch moves up the Brahmaputra valley in the north and the northeast, causing widespread rains. Its sub-branch strikes the Garo and Khasi hills of Meghalaya. Mawsynram, located on the crest of Khasi hills, receives the highest average annual rainfall in the world. Here it is important to know why the Tamil Nadu coast remains dry during this season. There are two factors responsible for it: (i) The Tamil Nadu coast is situated parallel to the Bay of Bengal branch of southwest monsoon. (ii) It lies in the rainshadow area of the Arabian Sea branch of the south-west monsoon. Characteristics of Monsoonal Rainfall (i) Rainfall received from the southwest monsoons is seasonal in character, which occurs between June and September. (ii) Monsoonal rainfall is largely governed by relief or topography. For instance the windward side of the Western Ghats register a rainfall of over 250 cm. Again, the heavy rainfall in the northeastern states can be attributed to their hill ranges and the Eastern Himalayas.

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Figure 4.10 : India : Seasonal Rainfall (June-September)

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(iii) The monsoon rainfall has a declining trend with increasing distance from the sea. Kolkata receives 119 cm during the southwest monsoon period, Patna 105 cm, Allahabad 76 cm and Delhi 56 cm. (iv) The monsoon rains occur in wet spells of few days duration at a time. The wet spells are interspersed with rainless interval known as ‘breaks’. These breaks in rainfall are related to the cyclonic depressions mainly formed at the head of the Bay of Bengal, and their crossing into the mainland. Besides the frequency and intensity of these depressions, the passage followed by them determines the spatial distribution of rainfall. (v) The summer rainfall comes in a heavy downpour leading to considerable run off and soil erosion. (vi) Monsoons play a pivotal role in the agrarian economy of India because over three-fourths of the total rain in the country is received during the southwest monsoon season. (vii) Its spatial distribution is also uneven which ranges from 12 cm to more than 250 cm. (viii) The beginning of the rains sometimes is considerably delayed over the whole or a part of the country. (ix) The rains sometimes end considerably earlier than usual, causing great damage to standing crops and making the sowing of winter crops difficult. Season of Retreating Monsoon The months of October and November are known for retreating monsoons. By the end of September, the southwest monsoon becomes weak as the low pressure trough of the Ganga plain starts moving southward in response to the southward march of the sun. The monsoon retreats from the western Rajasthan by the first week of September. It withdraws from Rajasthan, Gujarat, Western Ganga plain and the Central Highlands by the end of the month. By the beginning of October, the low pressure covers northern parts of the Bay of Bengal and by early November, it moves

over Karnataka and Tamil Nadu. By the middle of December, the centre of low pressure is completely removed from the Peninsula. The retreating southwest monsoon season is marked by clear skies and rise in temperature. The land is still moist. Owing to the conditions of high temperature and humidity, the weather becomes rather oppressive. This is commonly known as the ‘October heat’. In the second half of October, the mercury begins to fall rapidly, particularly in northern India. The weather in the retreating monsoon is dry in north India but it is associated with rain in the eastern part of the Peninsula. Here, October and November are the rainiest months of the year. The widespread rain in this season is associated with the passage of cyclonic depressions which originate over the Andaman Sea and manage to cross the eastern coast of the southern Peninsula. These tropical cyclones are very destructive. The thickly populated deltas of the Godavari, Krishna and Kaveri are their preferred targets. Every year cyclones bring disaster here. A few cyclonic storms also strike the coast of West Bengal, Bangladesh and Myanmar. A bulk of the rainfall of the Coromondal coast is derived from these depressions and cyclones. Such cyclonic storms are less frequent in the Arabian Sea.

TRADITIONAL INDIAN SEASONS In the Indian tradition, a year is divided into six two-monthly seasons. This cycle of seasons, which the common people in north and central India follow is based on their practical experience and age-old perception of weather phenomena. However, this system does not match with the seasons of south India where there is little variation in the seasons. Seasons

Months (According to the Indian Calendar)

Months (According to the Indian Calendar)

Vasanta Grishma Varsha Sharada Hemanta Shishira

Chaitra-Vaisakha Jyaistha-Asadha Sravana-Bhadra Asvina-Kartika Margashirsa-Pausa Magha-Phalguna

March-April May-June July-August September-October November-December January-February

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Distribution of Rainfall The average annual rainfall in India is about 125 cm, but it has great spatial variations (Figure 4.11). Areas of High Rainfall : The highest rainfall occurs along the west coast, on the Western Ghats, as well as in the sub-Himalayan areas is the northeast and the hills of Meghalaya. Here the rainfall exceeds 200 cm. In some parts of Khasi and Jaintia hills, the rainfall exceeds 1,000 cm. In the Brahmaputra valley and the adjoining hills, the rainfall is less then 200 cm. Areas of Medium Rainfall : Rainfall between 100-200 cm is received in the southern parts of Gujarat, east Tamil Nadu, northeastern Peninsula covering Orissa, Jharkhand, Bihar, eastern Madhya Pradesh, northern Ganga plain along the sub-Himalayas and the Cachar Valley and Manipur. Areas of Low Rainfall : Western Uttar Pradesh, Delhi, Haryana, Punjab, Jammu and Kashmir, eastern Rajasthan, Gujarat and Deccan Plateau receive rainfall between 50-100 cm. Areas of Inadequate Rainfall: Parts of the Peninsula, especially in Andhra Pradesh, Karnataka and Maharashtra, Ladakh and most of western Rajasthan receive rainfall below 50 cm. Snowfall is restricted to the Himalayan region. Identify the pattern of rainfall after consulting the rainfall map. Variability of Rainfall A characteristic feature of rainfall in India is its variability. The variability of rainfall is computed with the help of the following formula: C.V. =

Standard Deviation × 100 Mean

where C.V. is the coefficient of variation. The values of coefficient of variation show the change from the mean values of rainfall. The actual rainfall in some places deviates from 20-50 per cent. The values of coefficient of variation show variability of rainfall in India. A variability of less than 25 per cent exists on the western coasts, Western Ghats, northeastern

Peninsula, eastern plains of the Ganga, northeastern India, Uttaranchal and Himachal Pradesh and south-western part of Jammu and Kashmir. These areas have an annual rainfall of over 100 cm. A variability of over 50 per cent exists in the western part of Rajasthan, northern part of Jammu and Kashmir and interior parts of the Deccan plateau. These areas have an annual rainfall of less than 50 cm. Rest of India have a variability of 25-50 per cent and these areas receive an annual rainfall between 50 -100 cm (Figure 4.12). Climatic Regions of India The whole of India has a monsoon type of climate. But the combination of elements of the weather, however, reveal many regional variations. These variations represent the subtypes of the monsoon climate. It is on this basis that the climatic regions can be identified. A climatic region has a homogeneous climatic condition which is the result of a combination of factors. Temperature and rainfall are two important elements which are considered to be decisive in all the schemes of climatic classification. The classification of climate, however, is a complex exercise. There are different schemes of classification of climate. Major climatic types of India based on Koeppen’s scheme have been described below: Koeppen based his scheme of Climatic classification on monthly values of temperature and precipitation. He identified five major climatic types, namely: (i) Tropical climates, where mean monthly temperature throughout the year is over 18°C. (ii) Dry climates, where precipitation is very low in comparison to temperature, and hence, dry. If dryness is less, it is semiarid (S); if it is more, the climate is arid(W). (iii) Warm temperate climates, where mean temperature of the coldest month is between 18°C and minus 3°C. (iv) Cool temperate climates, where mean temperature of the warmest month is over 10°C, and mean temperature of the coldest month is under minus 3°C. (v) Ice climates, where mean temperature of the warmest month is under 10°C.

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Figure 4.11 : India : Annual Rainfall

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Figure 4.12 : India : Variability of Annual Rainfall

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Koeppen used letter symbols to denote climatic types as given above. Each type is further sub-divided into sub-types on the basis of seasonal variations in the distributional pattern of rainfall and temperature. He used S for semi-arid and W for arid and the following small letters to define sub-types: f (sufficient precipitation), m (rain forest despite a dry monsoon season), w (dry season in winter), h (dry and hot), c (less than four months with mean temperature over 10°C), and g (Gangetic plain). Accordingly, India can be divided into eight climatic regions (Table 4.1; Figure 4.13).

(vii) Winter rainfall by temperate cyclones in north India is highly beneficial for rabi crops. (viii) Regional climatic variation in India is reflected in the vast variety of food, clothes and house types.

GLOBAL WARMING You know that change is the law of nature. Climate has also witnessed change in the past at the global as well as at local levels. It is changing even now but the change is imperceptible. A number of geological evidences suggest that once upon a time,

Table 4.1 : Climatic Regions of India According to Koeppen’s Scheme Type of Climate Amw Monsoon with short dry season As – Monsoon with dry summer Aw – Tripical savannah Bwhw – Semi-arid steppe climate Bwhw – Hot desert Cwg – Monsoon with dry winter Dfc – Cold humid winter with short summer E – Polar type

Areas West coast of India south of Goa Coromandel coast of Tamil Nadu Most of the Peninsular plateaus, south of the Tropic of Cancer North-western Gujarat, some parts of western Rajasthan and Punjab Extreme western Rajasthan Ganga plain, eastern Rajasthan, northern Madhya Pradesh, most of North-east India Arunachal Pradesh Jammu and Kashmir, Himachal Pradesh and Uttaranchal

Monsoons and the Economic Life in India (i) Monsoon is that axis around which revolves the entire agricultural cycle of India. It is because about 64 per cent people of India depend on agriculture for their livelihood and agriculture itself is based on southwest monsoon. (ii) Except Himalayas all the parts of the country have temperature above the threashold level to grow the crops or plants throughout the year.. (iii) Regional variations in monsoon climate help in growing various types of crops. (iv) Variability of rainfall brings droughts or floods every year in some parts of the country. (v) Agricultural prosperity of India depends very much on timely and adequately distributed rainfall. If it fails, agriculture is adversely affected particularly in those regions where means of irrigation are not developed. (vi) Sudden monsoon burst creates problem of soil erosion over large areas in India.

(see geological time scale in Chapter 2 of Fundamentals of Physical Geography, NCERT, 2006) large part of the earth was under ice cover. Now you might have read or heard the debate on global warming. Besides the natural causes, human activities such as large scale industrialisation and presence of polluting gas in the atmosphere are also important factors responsible for global warming. You might have heard about the “green house effect” while discussing global warming. The temperature of the world is significantly increasing. Carbon dioxide produced by human activities is a major source of concern. This gas, released to the atmosphere in large quantities by burning of fossil fuel, is increasing gradually. Other gases like methane, chlorofluorocarbons, and nitrous oxide which are present in much smaller concentrations in the atmosphere, together with carbon dioxide are known as green house gases. These gases are better absorbers of long wave radiations than carbon

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Figure 4.13 : India : Climatic Regions According to Koppen’s Scheme

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ice melt in response to warming. According to the current prediction, on an average, the sea level will rise 48 cm by the end of twenty first century. This would increase the incidence of annual flooding. Climatic change would promote insect-borne diseases like malaria, and lead to shift in climatic boundaries, making some regions wetter and others drier. Agricultural pattern would shift and human population as well as the ecosystem would experience change. What would happen to the Indian sea coasts if the sea level rises 50 cm above the present one?

dioxide, and so, are more effective at enhancing the green house effect. These gases have been contributing to global warming. It is said that due to global warming the polar ice caps and mountain glaciers would melt and the amount of water in the oceans would increase. The mean annual surface temperature of the earth in the past 150 years has increased. It is projected that by the year 2,100, global temperature will warm about 2°C. This rise in temperature will accompany many other changes: one of these is a rise in sea level, as glacier and sea

EXERCISES

1.

Choose the right answer from the four alternatives given below. (i)

What causes rainfall on the coastal areas of Tamil Nadu in the beginning of winters? (a) South-West monsoon (c) North-Eastern monsoon (b)

(ii)

Temperate cyclones

Local air circulation

What is the proportion of area of India which receives annual rainfall less than 75 cm? (a) Half (c) Two-third (b) One-third

(iii)

(d)

(d)

Three-fourth

Which one of the following is not a fact regarding South India? (a) Diurnal range of temperature is less here. (b) Annual range of temperature is less here. (c)

Temperatures here are high throughout the year.

(d) Extreme climatic conditions are found here. (iv)

Which one of the following phenomenon happens when the sun shines vertically over the Tropic of Capricorn in the southern hemisphere? (a) High pressure develops over North-western India due to low temperatures. (b) Low pressure develops over North-western India due to high temperatures. (c) No changes in temperature and pressure occur in north-western India. (d) ‘Loo’ blows in the North-western India.

(v)

In which of the following states in India do we find ‘As’ type of climate as per Koeppen’s classification? (a) In Kerala and coastal Karnataka (b) In Andaman and Nicobar Islands (c) On Coromandal coast (d) In Assam and Arunachal Pradesh

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2.

3.

Answer the following questions in about 30 words. (i) What are the three important factors which influence the mechanism of Indian weather? (ii) What is the Inter-Tropical Convergene Zone? (iii) What is meant by ‘bursting of monsoon’? Name the place of India which gets the highest rainfall. (iv) Define ‘climatic region’? What are the bases of Koeppen’s classification? (v) Which type(s) of cyclones cause rainfall in north-western India during winter? Where do they originate? Answer the following questions in not more than 125 words. (i) (ii)

Notwithstanding the broad climatic unity, the climate of India has many regional variations. Elaborate this statement giving suitable examples. How many distinct seasons are found in India as per the Indian Meteorological Department? Discuss the weather conditions associated with any one season in detail.

Project/Activity On the outline map of India, show the following: (i) Areas of winter rain (ii) Wind direction during the summer season (iii) Areas having variability of rainfall over 50 per cent (iv) Areas having less than 15°C temperature in January (v) Isohyte of 100 cm.

CHAPTER

NATURAL VEGETATION

H

ave you ever been to a forest for a picnic? You might have surely gone to a park if you live in a city or to a mango, guava or coconut orchard, if you live in a village. How do you differentiate between the natural vegetation and the planted vegetation? The same variety may be found growing wild in the forest under natural conditions and the same tree may be the planted one in your garden under human supervision. Natural vegetation refers to a plant community that has been left undisturbed over a long time, so as to allow its individual species to adjust themselves to climate and soil conditions as fully as possible. India is a land of great variety of natural vegetation. Himalayan heights are marked with temperate vegetation; the Western Ghats and the Andaman Nicobar Islands have tropical rain forests, the deltaic regions have tropical forests and mangroves; the desert and semi desert areas of Rajasthan are known for cactii, a wide variety of bushes and thorny vegetation. Depending upon the variations in the climate and the soil, the vegetation of India changes from one region to another. On the basis of certain common features such as predominant vegetation type and climatic regions, Indian forests can be divided into the following groups:

Tropical Evergreen and Semi Evergreen Forests These forests are found in the western slope of the Western Ghats, hills of the northeastern region and the Andaman and Nicobar Islands. They are found in warm and humid areas with an annual precipitation of over 200 cm and mean annual temperature above 22 oC. Tropical evergreen forests are well stratified, with layers closer to the ground and are covered with shrubs and creepers, with short structured trees followed by tall variety of trees. In these forests, trees reach great heights up to 60 m or above. There is no definite time for trees to shed their leaves, flowering and fruition. As such these forests appear green all the year round. Species found in these forests include rosewood, mahogony, aini, ebony, etc. The semi evergreen forests are found in the less rainy parts of these regions. Such forests have a mixture of evergreen and moist deciduous trees. The undergrowing climbers provide an evergreen character to these forests. Main species are white cedar, hollock and kail.

TYPES OF FORESTS (i) Tropical Evergreen and Semi Evergreen forests (ii) Tropical Deciduous forests (iii) Tropical Thorn forests (iv) Montane forests (v) Littoral and Swamp forests.

Figure 5.1 : Evergreen Forest

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Figure 5.2 : Natural Vegetation

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The British were aware of the economic value of the forests in India, hence, large scale exploitation of these forests was started. The structure of forests was also changed. The oak forests in Garhwal and Kumaon were replaced by pine (chirs) which was needed to lay railway lines. Forests were also cleared for introducing plantations of tea, rubber and coffee. The British also used timber for construction activities as it acts as an insulator of heat. The protectional use of forests was, thus, replaced by commercial use. Tropical Deciduous Forests These are the most widespread forests in India. They are also called the monsoon forests. They spread over regions which receive rainfall between 70-200 cm. On the basis of the availability of water, these forests are further divided into moist and dry deciduous.

the plains of Uttar Pradesh and Bihar. In the higher rainfall regions of the Peninsular plateau and the northern Indian plain, these forests have a parkland landscape with open stretches in which teak and other trees interspersed with patches of grass are common. As the dry season begins, the trees shed their leaves completely and the forest appears like a vast grassland with naked trees all around. Tendu, palas, amaltas, bel, khair, axlewood, etc. are the common trees of these forests. In the western and southern part of Rajasthan, vegetation cover is very scanty due to low rainfall and overgrazing. Tropical Thorn Forests Tropical thorn forests occur in the areas which receive rainfall less than 50 cm. These consist of a variety of grasses and shrubs. It includes semi-arid areas of south west Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh and Uttar Pradesh. In these forests, plants remain leafless for most part of the year and give an expression of scrub vegetation. Important species found are babool, ber, and wild date palm, khair, neem, khejri, palas, etc. Tussocky grass grows upto a height of 2 m as the under growth.

Figure 5.3 : Deciduous Forests

The Moist deciduous forests are more pronounced in the regions which record rainfall between 100-200 cm. These forests are found in the northeastern states along the foothills of Himalayas, eastern slopes of the Western Ghats and Orissa. Teak, sal, shisham, hurra, mahua, amla, semul, kusum, and sandalwood etc. are the main species of these forests. Dry deciduous forest covers vast areas of the country, where rainfall ranges between 70 -100 cm. On the wetter margins, it has a transition to the moist deciduous, while on the drier margins to thorn forests. These forests are found in rainier areas of the Peninsula and

Figure 5.4 : Tropical Thorn Forests

Montane Forests In mountainous areas, the decrease in temperature with increasing altitude leads to a corresponding change in natural vegetation. Mountain forests can be classified into two types, the northern mountain forests and the southern mountain forests.

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The Himalayan ranges show a succession of vegetation from the tropical to the tundra, which change in with the altitude. Deciduous forests are found in the foothills of the Himalayas. It is succeeded by the wet temperate type of forests between an altitude of 1,000-2,000 m. In the higher hill ranges of northeastern India, hilly areas of West Bengal and Uttaranchal, evergreen broad leaf trees such as oak and chestnut are predominant. Between 1,500-1,750 m, pine forests are also well-developed in this zone, with Chir Pine as a very useful commercial tree. Deodar, a highly valued endemic species grows mainly in the western part of the Himalayan range. Deodar is a durable wood mainly used in construction activity. Similarly, the chinar and the walnut, which sustain the famous Kashmir handicrafts, belong to this zone. Blue pine and spruce appear at altitudes of 2,225-3,048 m. At many places in this zone, temperate grasslands are also found. But in the higher reaches there is a transition to Alpine forests and pastures. Silver firs, junipers, pines, birch and rhododendrons, etc. occur between 3,000-4,000 m. However, these pastures are used extensively for transhumance by tribes like the Gujjars, the Bakarwals, the Bhotiyas and the Gaddis. The southern slopes of the Himalayas carry a thicker vegetation cover because of relatively higher precipitation than the drier north-facing slopes. At higher altitudes, mosses and lichens form part of the tundra vegetation.

Figure 5.5 : Montane Forests

The southern mountain forests include the forests found in three distinct areas of Peninsular India viz; the Western Ghats, the Vindhyas and the Nilgiris. As they are closer to the tropics, and only 1,500 m above the sea level, vegetation is temperate in the higher regions, and subtropical on the lower regions of the Western Ghats, especially in Kerala, Tamil Nadu and Karnataka. The temperate forests are called Sholas in the Nilgiris, Anaimalai and Palani hills. Some of the other trees of this forest of economic significance include, magnolia, laurel, cinchona and wattle. Such forests are also found in the Satpura and the Maikal ranges. Littoral and Swamp Forests India has a rich variety of wetland habitats. About 70 per cent of this comprises areas under paddy cultivation. The total area of wet land is 3.9 million hectares. Two sites — Chilika Lake (Orissa) and Keoladeo National Park (Bharatpur) are protected as water-fowl habitats under the Convention of Wetlands of International Importance (Ramsar Convention). An international convention is an agreement among member states of the United Nations. The country’s wetlands have been grouped into eight categories, viz. (i) the reservoirs of the Deccan Plateau in the south together with the lagoons and other wetlands of the southern west coast; (ii) the vast saline expanses of Rajasthan, Gujarat and the Gulf of Kachchh; (iii) freshwater lakes and reservoirs from Gujarat eastwards through Rajasthan (Keoladeo National Park) and Madhya Pradesh; (iv) the delta wetlands and lagoons of India’s east coast (Chilika Lake); (v) the freshwater marshes of the Gangetic Plain; (vi) the floodplains of the Brahmaputra; the marshes and swamps in the hills of northeast India and the Himalayan foothills; (vii) the lakes and rivers of the montane region of Kashmir and Ladakh; and (viii) the mangrove forest and other wetlands of the island arcs of the Andaman and Nicobar Islands. Mangroves grow along the coasts in the salt marshes, tidal creeks, mud flats and estuaries.

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They consist of a number of salt-tolerant species of plants. Crisscrossed by creeks of stagnant water and tidal flows, these forests give shelter to a wide variety of birds.

Figure 5.6 : Mangrove Forests

In India, the mangrove forests spread over 6,740 sq. km which is 7 per cent of the world’s mangrove forests. They are highly developed in the Andaman and Nicobar Islands and the Sunderbans of West Bengal. Other areas of significance are the Mahanadi, the Godavari and the Krishna deltas. These forests too, are being encroached upon, and hence, need conservation.

FOREST COVER IN INDIA According to state records, the forest area covers 23.28 per cent of the total land area of the country. It is important to note that the forest area and the actual forest cover are not the same. The forest area is the area notified and recorded as the forest land irrespective of the existence of trees, while the actual forest cover is the area occupied by forests with canopy. The former is based on the records of the State Revenue Department, while the latter is based on aerial photographs and satellite imageries. In 2001, the actual forest cover was only 20.55 per cent. Of the forest cover, the share of dense and open forests was 12.60 per cent and 7.87 per cent rerspectively. Both forest area and forest cover vary from state to state. Lakshadweep has zero per cent forest area; Andaman and Nicobar Islands have 86.93 per cent. Most of the states with less than 10 per cent of the forest area lie in the north and northwestern part of the country. These are Rajasthan, Gujarat, Punjab, Haryana and Delhi.

Most of the forests in Punjab and Haryana have been cleared for cultivation. States with 10-20 per cent forest area are Tamil Nadu and West Bengal. In Peninsular India, excluding Tamil Nadu, Dadra and Nagar Haveli and Goa, the area under forest cover is 20-30 per cent. The northeastern states have more than 30 per cent of the land under forest. Hilly topography and heavy rainfall are good for forest growth. There is a lot of variation in actual forest cover, which ranges from 9.56 per cent in Jammu and Kashmir to 84.01 per cent in Andaman and Nicobar Islands. From the table showing the distribution of forests in India (Appendix IV), it is clear that there are 15 states where the forest cover is more than one-third of the total area, which is the basic requirement for maintaining the ecological balance. On the basis of the percentage of the actual forest cover, the states have been grouped into four regions: The Region

Percentage Cover of the Forest

(i) The region of high concentration

> 40

(ii) The region of medium concentration

20-40

(iii) The region of low concentration

10-20

(iv) The region of very low concentration

< 10

Taking the data from Appendix IV, list the states under the four regins of forest cover

FOREST CONSERVATION Forests have an intricate interrelationship with life and environment. These provide numerous direct and indirect advantages to our economy and society. Hence, conservation of forest is of vital importance to the survival and prosperity of humankind. Accordingly, the Government of India proposed to have a nation-wide forest conservation policy, and adopted a forest policy in 1952, which was further modified in 1988. According to the new forest policy, the Government will emphasise sustainable forest management in order to conserve and expand forest reserve on the one hand, and to meet the needs of local people on the other. The forest policy aimed at : (i) bringing 33 per cent of the geographical areas under forest

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INDIA : PHYSICAL ENVIRONMENT

cover; (ii) maintaining environmental stability and to restore forests where ecological balance was disturbed; (iii) conserving the natural heritage of the country, its biological diversity and genetic pool; (iv) checks soil erosion, extension of the desert lands and reduction of floods and droughts; (v) increasing the forest cover through social forestry and afforestation on degraded land; (vi) increasing the productivity of forests to make timber, fuel, fodder and food available to rural population dependant on forests, and encourage the substitution of wood; (vii) creating of a massive peoples movement involving women to encourage planting of trees, stop felling of trees and thus, reduce pressure on the existing forest. Forests and Life To a vast number of tribal people, the forest is a home, a livelihood, their very existence. It provides them food, fruits of all kinds, edible leaves, honey, nourishing roots and wild game. It provides them with material to build their houses and items for practising their arts. The importance of forests in tribal economy is well-known as they are the source of sustenance and livelihood for tribal communities. It is commonly believed that the tribal communities live in harmony with nature and protect forests. Out of a total of 593 districts 187 (2001) have been identified as tribal districts. The tribal districts account for about 59.8 per cent of the total forest cover of the country whereas the geographical area of 187 tribal districts forms only 33.6 per cent of the total geographical area of the country. It demonstrates that tribal districts are generally rich in forest cover. Forest and tribals are very closely related. The age-old knowledge of tribals regarding forestry can be used in the development of forests. Rather than treating tribals as minor forest produce collectors they should be made growers of minor forest produce and encouraged to participate in conservation.

Based on the forest conservation policy the following steps were initiated: Social Forestry Social forestry means the management and protection of forests and afforestation on barren lands with the purpose of helping in the environmental, social and rural development. The National Commission on Agriculture (1976) has classified social forestry into three categories. These are Urban forestry, Rural forestry and Farm forestry. Urban forestry pertains to the raising and management of trees on public and privately owned lands in and around urban centres such as green belts, parks, roadside avenues, industrial and commercial green belts, etc. Rural forestry lays emphasis on promotion of agro-forestry and community-forestry. Agro-forestry is the raising of trees and agriculture crops on the same land inclusive of the waste patches. It combines forestry with agriculture, thus, altering the simultaneous production of food, fodder, fuel, timber and fruit. Community forestry involves the raising of trees on public or community land such as the village pasture and temple land, roadside, canal bank, strips along railway lines, and schools etc. Community forestry programme aims at providing benefits to the community as a whole. Community forestry provides a means under which the people of landless classes can associate themselves in treeraising and thus, get those benefits which otherwise are restricted for landowners. Farm Forestry Farm forestry is a term applied to the process under which farmers grow trees for commercial and non-commercial purposes on their farm lands. Forest departments of various states distribute seedlings of trees free of cost to small and medium farmers. Several lands such as the margins of agricultural fields, grasslands and pastures, land around homes and cow sheds may be used for raising trees under non-commercial farm forestry.

NATURAL VEGETATION

WILDLIFE You would have visited a zoo and may have seen animals and birds in captivity. Wildlife of India is a great natural heritage. It is estimated that about 4-5 per cent of all known plant and animal species on the earth are found in India. The main reason for this remarkable diversity of life forms is the great diversity of the ecosystem which this country has preserved and supported through the ages. Over the years, their habitat has been disturbed by human activities and as a result, their numbers have dwindled significantly. There are certain species that are at the brink of extinction. Some of the important reasons of the declining of wildlife are as follows: (i) Industrial and technological advancement brought about a rapid increase in the exploitation of forest resources. (ii) More and more lands were cleared for agriculture, human settlement, roads, mining, reservoirs, etc. (iii) Pressure on forests mounted due to lopping for fodder and fuelwood and removal of small timber by the local people. (iv) Grazing by domestic cattle caused an adverse effect on wildlife and its habitat. (v) Hunting was taken up as a sport by the elite and hundreds of wild animals were killed in a single hunt. Now commercial poaching is rampant. (vi) Incidence of forest fire. It is being felt that conservation of wildlife is of great significance to the national as well as the world heritage along with the promotion of ecotourism. What steps have been initiated by the government in this direction?

WILDLIFE CONSERVATION IN INDIA The protection of wildlife has a long tradition in India. Many stories of Panchtantra and Jungle Books, etc. have stood the test of time relating to the love for wildlife. These have a profound impact on young minds.

63

In 1972, a comprehensive Wildlife Act was enacted, which provides the main legal framework for conservation and protection of wildlife in India. The two main objectives of the Act are; to provide protection to the endangered species listed in the schedule of the Act and to provide legal support to the conservation areas of the country classified as National parks, sanctuaries and closed areas. This Act has been comprehensively amended in 1991, making punishments more stringent and has also made provisions for the protection of specified plant species and conservation of endangered species of wild animals. There are 92 National parks and 492 wildlife sanctuaries covering an area of 15.67 million hectares in the country. Wildlife conservation has a very large ambit with unbounded potential for the wellbeing of humankind. However, this can be achieved only when every individual understands its significance and contributes his bit. For the purpose of effective conservation of flora and fauna, special steps have been initiated by the Government of India in collaboration with UNESCO’s ‘Man and Biosphere Programme’. Special schemes like Project Tiger (1973) and Project Elephant (1992) have been launched to conserve these species and their habitat in a sustainable manner. Project Tiger has been implemented since 1973. The main objective of the scheme is to ensure maintenance of viable population of tigers in India for scientific, aesthetic, cultural and ecological values, and to preserve areas of biological importance as natural heritage for the benefit, education and enjoyment of the people. Initially, the Project Tiger was launched in nine tiger reserves, covering an area of 16,339 sq. km, which has now increased to 27 tiger reserves, encompassing 37,761sq. km of tiger habitats distributed in 17 states. The tiger population in the country has registered an increase from 1,827 in 1972 to 3,642 in 2001-2002.

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INDIA : PHYSICAL ENVIRONMENT

Project Elephant was launched in 1992 to assist states having free ranging population of wild elephants. It was aimed at ensuring long-term survival of identified viable population of elephants in their natural habitat. The project is being implemented in 13 states.

BIOSPHERE RESERVES A Biosphere Reserve is a unique and representative ecosystem of terrestrial and coastal areas which are internationally recognised within the framework of UNESCO’s Man and Biosphere (MAB) Programme. The Biosphere Reserve aims at achieving the three objectives as depicted in Figure 5.8. There are 14 Biosphere Reserves in India (Table 5.1, Figure 5.9). Four Biosphere Reserves, namely (i) Nilgiri; (ii) Nanda Devi;

Figure 5.7 : Elephants in their Natural Habitat

Apart from this, some other projects such as Crocodile Breeding Project, Project Hangul and conservation of Himalayan Musk deer have also been launched by the Government of India.

Figure 5.8 : Objectives of a Biosphere Reserve

Table 5.1 : List of Biosphere Reserves Sl. No. 1.

Name of the Biosphere Reserve * Nilgiri

Total Geographical Area (km2) 5,520

Location (States)

Part of Wynad, Nagarhole, Bandipur and Mudumalai, Nilambur, Silent Valley and Siruvani Hills (Tamil Nadu, Kerala and Karnataka) 2. * Nanda Devi 2,236.74 Part of Chamoli, Pithoragarh and Almora districts (Uttar Pradesh) and part of Garo Hills (Meghalaya) 3. Nokrek 820 Part of Garo Hills (Meghalaya) 4. Manas 2,837 Part of Kokrajhar, Bongaigaon, Barpeta, Nalbari, Kamrup and Darrang districts (Assam) 5. * Sunderbans 9,630 Part of delta of Ganges and Brahmaputra river system (West Bengal) 6. * Gulf of Mannar 10,500 Indian part of Gulf of Mannar between India and Sri Lanka (Tamil Nadu) 7. Great Nicobar 885 Southernmost islands of the Andaman and Nicobar (A & N Islands) 8. Similipal 4,374 Part of Mayurbhanj district (Orissa) 9. Dibru-Saikhowa 765 Part of Dibrugarh and Tinsukia districts (Assam) 10. Dihang Dibang 5,111.5 Part of Siang and Debang valley in Arunachal Pradesh 11. Kanchenjunga 2,619.92 Parts of North and West Sikkim 12. Pachmari 4,926.28 Parts of Betul, Hoshangabad and Chindwara districts of Madhya Pradesh 13. Agasthyamalai 1,701 Agasthyamalai Hills in Kerala 14. Achanakmar- Amarkantak 3,835.51 Parts of Anupur and Dindori district of MP and parts of Bilaspur district of Chhattisgarh * have been recognised by the UNESCO on World Network of Biosphere Reserves Source : Annual Report (2004-05), Ministry of Environment and Forests, Government of India

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NATURAL VEGETATION

Figure 5.9 : India : Biosphere Reserves

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INDIA : PHYSICAL ENVIRONMENT

(iii) Sunderbans; and (iv) Gulf of Mannar have been recognised by the UNESCO on World Network of Biosphere Reserves. Nilgiri Biosphere Reserve The Nilgiri Biosphere Reserve (NBR), the first of the fourteen biosphere reserves of India, was established in September 1986. It embraces the sanctuary complex of Wyanad, Nagarhole, Bandipur and Mudumalai, the entire forested hill slopes of Nilambur, the Upper Nilgiri plateau, Silent Valley and the Siruvani hills. The total area of the biosphere reserve is around 5,520 sq. km. The Nilgiri Biosphere Reserve possesses different habitat types, unspoilt areas of natural vegetation types with several dry scrubs, dry and moist deciduous, semievergreen and wet evergreen forests, evergreen sholas, grasslands and swamps. It includes the largest known population of two endangered animal species, namely the Nilgiri Tahr and the Lion-tailed macaque. The largest south Indian population of elephant, tiger, gaur, sambar and chital as well as a good number of endemic and endangered plants are also found in this reserve. The habitat of a number of tribal groups remarkable for their traditional modes of harmonious use of the environment are also found here. The topography of the NBR is extremely varied, ranging from an altitude of 250 m to 2,650 m. About 80 per cent of the flowering plants reported from the Western Ghats occur in the Nilgiri Biosphere Reserve. Nanda Devi Biosphere Reserve The Nanda Devi Biosphere Reserve situated in Uttaranchal includes parts of Chamoli, Almora, Pithoragarh and Bageshwar districts. The major forest types of the reserve are temperate. A few important species are silver

weed and orchids like latifolie and rhododendron. The biosphere reserve has a rich fauna, for example the snow leopard, black bear, brown bear, musk deer, snowcock, golden eagle and black eagle. Major threats to the ecosystem are the collection of endangered plants for medicinal use, forest fires and poaching. Sunderbans Biosphere Reserve It is located in the swampy delta of the river Ganga in West Bengal. It extends over a vast area of 9,630 sq. km and consists of mangrove forests, swamps and forested islands. Sunderbans is the home of nearly 200 Royal Bengal tigers. The tangled mass of roots of mangrove trees provide safe homes for a large number of species, from fish to shrimp. More than 170 birds species are known to inhabit these mangrove forests. Adapting itself to the saline and fresh water environment, the tigers at the park are good swimmers, and they hunt scarce preys such as chital deer, barking deer, wild pig and even macaques. In the Sunderbans, the mangrove forests are characterised by Heritiera fomes, a species valued for its timber. Gulf of Mannar Biosphere Reserve The Gulf of Mannar Biosphere Reserve covers an area of 105,000 hectares on the southeast coast of India. It is one of the world’s richest regions from a marine biodiversity perspective. The biosphere reserve comprises 21 islands with estuaries, beaches, forests of the nearshore environment, sea grasses, coral reefs, salt marshes and mangroves. Among the Gulf’’s 3,600 plant and animal species are the globally endangered sea cow (Dugong dugon) and six mangrove species, endemic to Peninsular India.

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i)

Sandalwood is an example of: (a) Evergreen forest (b) Deciduous forest

(c) Deltaic forest (d) Thorny forest

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NATURAL VEGETATION

(ii)

Which one of the following was the purpose of Project Tiger? (a) to kill tigers (c) to protect tigers from illegal hunting (b) to put tigers in the Zoo (d) to make films on tigers

(iii)

In which one of the following states is the Nandadevi Biosphere reserve situated? (a) (b)

(iv)

3.

One Two

(c) Three (d) Four

Which one of the following proportion of area of the country was targeted to be under forest in Forest Policy of India? (a) (b)

2.

(c) Uttaranchal (d) Orissa

How many of the following numbers of Biosphere reserves are recognised by the IUCN? (a) (b)

(v)

Bihar Uttar Pradesh

33 44

(c) 55 (d) 22

Answer the following questions in about 30 words. (i) What is natural vegetation? Under what climatic conditions are tropical evergreen forests develop? (ii) What do you understand by social forestry? (iii) Define Biosphere reserves? (iv) What is the difference between forest area and forest cover? Answer the following questions in not more than 150 words. (i) (ii)

What steps have been taken up to conserve forests? How can people’s participation be effective in conserving forests and wildlife?

Project/Activity 1. On the outline map of India, mark and label the following. (i) Areas having Mangrove forests. (ii) Biosphere reserves of Nanda Devi, Sunderbans, Gulf of Mannar and Nilgiri. (iii) Mark the location of Forest Survey of India Head Quarter. 2. List the trees, bush and shrub species found around your school. Write their local names and their uses.

CHAPTER

SOILS

H

ave you ever thought about the most important factor which supports trees, grasses, crops and numerous lifeforms over the earth’s surface? Can one grow a blade of grass without soil? While some plants and organisms which are aquatic in nature can sustain in water, do they not derive nutrients from soil through water? You will realise that soil is the most important layer of the earth’s crust. It is a valuable resource. The bulk of our food and much of our clothing is derived from land-based crops that grow in the soil. The soil on which we depend so much for our day-to-day needs has evolved over thousands of years. The various agents of weathering and gradation have acted upon the parent rock material to produce a thin layer of soil. Soil is the mixture of rock debris and organic materials which develop on the earth’s surface. The major factors affecting the formation of soil are relief, parent material, climate, vegetation and other life-forms and time. Besides these, human activities also influence it to a large extent. Components of the soil are mineral particles, humus, water and air. The actual amount of each of these depend upon the type of soil. Some soils are deficient in one or more of these, while there are some others that have varied combinations. Have you ever dug a pit in the field of your school to plant a tree while celebrating VanMahotsava? Was the pit of uniform layer of soil or did you notice different colours from the top to the bottom of the pit? If we dig a pit on land and look at the soil, we find that it consists of three layers which

are called horizons. ‘Horizon A’ is the topmost zone, where organic materials have got incorporated with the mineral matter, nutrients and water, which are necessary for the growth of plants. ‘Horizon B’ is a transition zone between the ‘horizon A’ and ‘horizon C’, and contains matter derived from below as well as from above. It has some organic matter in it, although the mineral matter is noticeably weathered. ‘Horizon C’ is composed of the loose parent material. This layer is the first stage in the soil formation process and eventually forms the above two layers. This arrangement of layers is known as the soil profile. Underneath these three horizons is the rock which is also known as the parent rock or the bedrock. Soil, which is a complex and varied entity has always drawn the attention of the scientists. In order to understand its importance, it is essential to attempt a scientific study of the soil. Classification of the soil is an effort to achieve this objective.

CLASSIFICATION

OF

SOILS

India has varied relief features, landforms, climatic realms and vegetation types. These have contributed in the development of various types of soils in India. In ancient times, soils used to be classified into two main groups – Urvara and Usara, which were fertile and sterile, respectively. In the 16th centrury A.D., soils were classified on the basis of their inherent characteristics and external features such as texture, colour, slope of land and moisture content in the soil. Based on texture, main soil types were identified as

69

SOILS

sandy, clayey, silty and loam, etc. On the basis of colour, they were red, yellow, black, etc. Since Independence, scientific surveys of soils have been conducted by various agencies. Soil Survey of India, established in 1956, made comprehensive studies of soils in selected areas like in the Damodar Valley. The National Bureau of Soil Survey and the Land Use Planning an Institute under the control of the Indian Council of Agricultural Research (ICAR) did a lot of studies on Indian soils. In their effort to study soil and to make it comparable at the international level, the ICAR has classified the Indian soils on the basis of their nature and character as per the United States Department of Agriculture (USDA) Soil Taxonomy.

about 40 per cent of the total area of the country. They are depositional soils, transported and deposited by rivers and streams. Through a narrow corridor in Rajasthan, they extend into the plains of Gujarat. In the Peninsular region, they are found in deltas of the east coast and in the river valleys.

ICAR has classified the soils of India into the following order as per the USDA soil taxonomy Sl. No.

Order

Area (in Thousand Hectares)

Percentage

Figure 6.1 : Alluvial Soil

(i)

Inceptisols

130372.90

39.74

(ii)

Entisols

92131.71

28.08

(iii)

Alfisols

44448.68

13.55

(iv)

Vertisols

27960.00

8.52

(v)

Aridisols

14069.00

4.28

(vi)

Ultisols

8250.00

2.51

(vi)

Mollisols

1320.00

0.40

Others

9503.10

2.92

(viii)

Total 100 Source : Soils of India, National Bureau of Soil Survey and Land Use Planning, Publication Number 94

On the basis of genesis, colour, composition and location, the soils of India have been classified into: (i) Alluvial soils (ii) Black soils (iii) Red and Yellow soils (iv) Laterite soils (v) Arid soils (vi) Saline soils (vii) Peaty soils (viii) Forest soils. Alluvial Soils Alluvial soils are widespread in the northern plains and the river valleys. These soils cover

The alluvial soils vary in nature from sandy loam to clay. They are generally rich in potash but poor in phosphorous. In the Upper and Middle Ganga plain, two different types of alluvial soils have developed, viz. Khadar and Bhangar. Khadar is the new alluvium and is deposited by floods annually, which enriches the soil by depositing fine silts. Bhangar represents a system of older alluvium, deposited away from the flood plains. Both the Khadar and Bhangar soils contain calcareous concretions (Kankars). These soils are more loamy and clayey in the lower and middle Ganga plain and the Brahamaputra valley. The sand content decreases from the west to east. The colour of the alluvial soils varies from the light grey to ash grey. Its shades depend on the depth of the deposition, the texture of the materials, and the time taken for attaining maturity. Alluvial soils are intensively cultivated. Black Soil Black soil covers most of the Deccan Plateau which includes parts of Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh and some parts of Tamil Nadu. In the upper reaches of the Godavari and the Krishna, and the north

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INDIA : PHYSICAL ENVIRONMENT

Figure 6.2 : Major Soil Types of India

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SOILS

western part of the Deccan Plateau, the black soil is very deep. These soils are also known as the ‘Regur Soil’ or the ‘Black Cotton Soil’. The black soils are generally clayey, deep and impermeable. They swell and become sticky when wet and shrink when dried. So, during the dry season, these soil develop wide cracks. Thus, there occurs a kind of ‘self ploughing’. Because of this character of slow absorption and loss of moisture, the black soil retains the moisture for a very long time, which helps the crops, especially, the rain fed ones, to sustain even during the dry season.

Figure 6.3 : Black Soil During Dry Season

Chemically, the black soils are rich in lime, iron, magnesia and alumina. They also contain potash. But they lack in phosphorous, nitrogen and organic matter. The colour of the soil ranges from deep black to grey. Red and Yellow Soil Red soil develops on crystalline igneous rocks in areas of low rainfall in the eastern and southern part of the Deccan Plateau. Along the piedmont zone of the Western Ghat, long stretch of area is occupied by red loamy soil. Yellow and red soils are also found in parts of Orissa and Chattisgarh and in the southern parts of the middle Ganga plain. The soil develops a reddish colour due to a wide diffusion of iron in crystalline and metamorphic rocks. It looks yellow when it occurs in a hydrated form. The fine-grained red and yellow soils are normally fertile, whereas coarse-grained soils found in dry upland areas are poor in fertility. They are generally poor in nitrogen, phosphorous and humus.

Laterite Soil Laterite has been derived from the Latin word ‘Later’ which means brick. The laterite soils develop in areas with high temperature and high rainfall. These are the result of intense leaching due to tropical rains. With rain, lime and silica are leached away, and soils rich in iron oxide and aluminium compound are left behind. Humus content of the soil is removed fast by bacteria that thrives well in high temperature. These soils are poor in organic matter, nitrogen, phosphate and calcium, while iron oxide and potash are in excess. Hence, laterites are not suitable for cultivation; however, application of manures and fertilisers are required for making the soils fertile for cultivation. Red laterite soils in Tamil Nadu, Andhra Pradesh and Kerala are more suitable for tree crops like cashewnut. Laterite soils are widely cut as bricks for use in house construction. These soils have mainly developed in the higher areas of the Peninsular plateau. The laterite soils are commonly found in Karnataka, Kerala, Tamil Nadu, Madhya Pradesh and the hilly areas of Orissa and Assam. Arid Soils Arid soils range from red to brown in colour. They are generally sandy in structure and saline in nature. In some areas, the salt content is so high that common salt is obtained by evaporating the saline water. Due to the dry climate, high temperature and accelerated evaporation, they lack moisture and humus. Nitrogen is insufficient and the phosphate

Figure 6.4 : Arid Soil

72

content is normal. Lower horizons of the soil are occupied by ‘kankar’ layers because of the increasing calcium content downwards. The ‘Kankar’ layer formation in the bottom horizons restricts the infiltration of water, and as such when irrigation is made available, the soil moisture is readily available for a sustainable plant growth. Arid soils are characteristically developed in western Rajasthan, which exhibit characteristic arid topography. These soils are poor and contain little humus and organic matter. Saline Soils They are also known as Usara soils. Saline soils contain a larger proportion of sodium, potassium and magnesium, and thus, they are infertile, and do not support any vegetative growth. They have more salts, largely because of dry climate and poor drainage. They occur in arid and semi-arid regions, and in waterlogged and swampy areas. Their structure ranges from sandy to loamy. They lack in nitrogen and calcium. Saline soils are more widespread in western Gujarat, deltas of the eastern coast and in Sunderban areas of West Bengal. In the Rann of Kuchchh, the Southwest Monsoon brings salt particles and deposits there as a crust. Seawater intrusions in the deltas promote the occurrence of saline soils. In the areas of intensive cultivation with excessive use of irrigation, especially in areas of green revolution, the fertile alluvial soils are becoming saline. Excessive irrigation with dry climatic conditions promotes capillary action, which results in the deposition of salt on the top layer of the soil. In such areas, especially in Punjab and Haryana, farmers are advised to add gypsum to solve the problem of salinity in the soil. Peaty Soils They are found in the areas of heavy rainfall and high humidity, where there is a good growth of vegetation. Thus, large quantity of dead organic matter accumulates in these areas, and this gives a rich humus and organic content to the soil. Organic matter in these soils may go even up to 40-50 per cent. These

INDIA : PHYSICAL ENVIRONMENT

soils are normally heavy and black in colour. At many places, they are alkaline also. It occurs widely in the northern part of Bihar, southern part of Uttaranchal and the coastal areas of West Bengal, Orissa and Tamil Nadu. Forest Soils As the name suggests, forest soils are formed in the forest areas where sufficient rainfall is available. The soils vary in structure and texture depending on the mountain environment where they are formed. They are loamy and silty on valley sides and coarse-grained in the upper slopes. In the snow-bound areas of the Himalayas, they experience denudation, and are acidic with low humus content. The soils found in the lower valleys are fertile. It is evident from the foregoing discussions that soils, their texture, quality and nature are vital for the germination and growth of plant and vegetation including crops. Soils are living systems. Like any other organism, they too develop and decay, get degraded, respond to proper treatment if administered in time. These have serious repercussions on other components of the system of which they themselves are important parts.

SOIL DEGRADATION In a broad sense, soil degradation can be defined as the decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse. Soil degradation is the main factor leading to the depleting soil resource base in India. The degree of soil degradation varies from place to place according to the topography, wind velocity and amount of the rainfall.

SOIL EROSION The destruction of the soil cover is described as soil erosion. The soil forming processes and the erosional processes of running water and wind go on simultaneously. But generally, there is a balance between these two processes. The rate of removal of fine particles from the surface is the same as the rate of addition of particles to the soil layer.

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SOILS

Sometimes, such a balance is disturbed by natural or human factors, leading to a greater rate of removal of soil. Human activities too are responsible for soil erosion to a great extent. As the human population increases, the demand on the land also increases. Forest and other natural vegetation is removed for human settlement, for cultivation, for grazing animals and for various other needs. Wind and water are powerful agents of soil erosion because of their ability to remove soil and transport it. Wind erosion is significant in arid and semi-arid regions. In regions with heavy rainfall and steep slopes, erosion by running water is more significant. Water erosion which is more serious and occurs extensively in different parts of India, takes place mainly in the form of sheet and gully erosion. Sheet erosion takes place on level lands after a heavy shower and the soil removal is not easily noticeable. But it is harmful since it removes the finer and more fertile top soil. Gully erosion is common on steep slopes. Gullies deepen with rainfall, cut the agricultural lands into small fragments and make them unfit for cultivation. A region with a large number of deep gullies or ravines is called a badland topography. Ravines are widespread, in the Chambal basin. Besides this, they are also found in Tamil Nadu and West Bengal. The country is losing about 8,000 hectares of land to ravines every year. What types are prone to gully erosion?

Soil erosion is a serious problem for Indian agriculture and its negative effects are seen in other spheres also. Eroded materials are carried down to rivers and they lower down their carrying capacity, and cause frequent floods and damage to agricultural lands. Deforestation is one of the major causes of soil erosion. Plants keep soils bound in locks of roots, and thus, prevent erosion. They also add humus to the soil by shedding leaves and twigs. Forests have been denuded practically in most parts of India but their effect on soil erosion are more in hilly parts of the country. A fairly large area of arable land in the irrigated zones of India is becoming saline because of overirrigation. The salt lodged in the lower profiles of the soil comes up to the surface and destroys its fertility. Chemical fertilisers in the absence of organic manures are also harmful to the soil. Unless the soil gets enough humus, chemicals harden it and reduce its fertility in the long run. This problem is common in all the command areas of the river valley projects, which were the first beneficiaries of the Green Revolution. According to estimates, about half of the total land of India is under some degree of degradation. Every year, India loses millions of tonnes of soil and its nutrients to the agents of its degradation, which adversely affects our national productivity. So, it is imperative to initiate immediate steps to reclaim and conserve soils. Soil Conservation

Figure 6.5 : Soil Erosion

If soil erosion and exhaustion are caused by humans; by corollary, they can also be prevented by humans. Nature has its own laws of maintaining balance. Nature offers enough opportunities for humans to develop their economy without disturbing the ecological balance. Soil conservation is a methodology to maintain soil fertility, prevent soil erosion and exhaustion, and improve the degraded condition of the soil. Soil erosion is essentially aggravated by faulty practices. The first step in any rational solution is to check open cultivable lands on slopes from farming. Lands with a slope gradient of 15 - 25 per cent should not be used

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for cultivation. If at all the land is to be used for agriculture, terraces should carefully be made. Over-grazing and shifting cultivation in many parts of India have affected the natural cover of land and given rise to extensive erosion. It should be regulated and controlled by educating villagers about the consequences. Contour bunding, Contour terracing, regulated forestry, controlled grazing, cover cropping, mixed farming and crop rotation are some of the remedial measures which are often adopted to reduce soil erosion.

Figure 6.6 : Terrace Farming

Efforts should be made to prevent gully erosion and control their formation. Finger gullies can be eliminated by terracing. In bigger gullies, the erosive velocity of water may

be reduced by constructing a series of check dams. Special attention should be made to control headward extension of gullies. This can be done by gully plugging, terracing or by planting cover vegetation. In arid and semi-arid areas, efforts should be made to protect cultivable lands from encroachment by sand dunes through developing shelter belts of trees and agro-forestry. Lands not suitable for cultivation should be converted into pastures for grazing. Experiments have been made to stabilise sand dunes in western Rajasthan by the Central Arid Zone Research Institute (CAZRI). The Central Soil Conservation Board, set up by the Government of India, has prepared a number of plans for soil conservation in different parts of the country. These plans are based on the climatic conditions, configuration of land and the social behaviour of people. Even these plans are fragmental in nature. Integrated land use planning, therefore, seems to be the best technique for proper soil conservation. Lands should be classified according to their capability; land use maps should be prepared and lands should be put to right uses. The final responsibility for achieving the conservation of land will rest on the people who operate on it and receive the benefits.

EXERCISES 1.

Choose the right answer from the (i) Which one of the following is category of soil? (a) Alluvial Soil (c) (b) Laterite Soil (d) (ii)

Black Soil Forest Soil

‘Regur Soil’ is another name for the. (a) Saline Soil (b) Arid Soil

(iii)

four alternatives given below. the most widespread and most productive

(c) Black Soil (d) Laterite Soil

Which one of the following is the main reason for the loss of the top soil in India? (a) Wind erosion (b) Water erosion

(c) Excessive leaching (d) None of these

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SOILS

(iv)

Arable land in the irrigated zones of India is turning saline due to which of the following reasons? (a) Addition of gypsum (b) Over grazing

2.

Answer the following questions in about 30 words. (i) (ii) (iii) (iv) (v)

3.

(c) Over irrigation (d) Use of fertilisers

What is soil? What are the main factors responsible for the formation of soil? Mention the three horizons of a soil profile. What is soil degradation? What is the difference between Khadar and Bhangar?

Answer the following questions in not more than 125 words. (i) (ii) (iii)

What are black soils? Describe their formation and characteristics. What is soil conservation? Suggest some measures to conserve soil. How do you know that a particular type of soil is fertile or not? Differentiate between naturally determined fertility and culturally induced fertility.

Project/Activity 1.

Collect various samples of soil and prepare a report on the type(s) of soils found in your region.

2.

On an outline map of India, mark the areas coverd by the following soil categories. (i) (ii) (iii)

Red soil Laterite soil Alluvial soil.

UNIT IV N ATURAL H AZARDS AND D ISASTERS : CAUSES, CONSEQUENCES AND MANAGEMENT This unit deals with • • • •

Floods and droughts Earthquakes and tsunami Cyclones Landslides

CHAPTER

NATURAL HAZARDS

Y

AND

DISASTERS

ou might have read about tsunami or seen the images of horror on television set immediately after it happened. You may also be aware of the severe earthquake in Kashmir on both sides of the Line of Control (LOC). The damage caused to human life and properties during these episodes has moved us all. What are these as phenomena and how they are caused? How can we save ourselves? These are some questions which come to our minds. This chapter will attempt to analyse some of these questions. Change is the law of nature. It is a continuous process that goes on uninterruptedly involving phenomena, big and small, material and nonmaterial that make our physical and sociocultural environment. It is a process present everywhere with variations in terms of magnitude, intensity and scale. Change can be a gradual or slow process like the evolution of landforms and organisms and it can be as sudden and swift as volcanic eruptions, tsunamis, earthquakes and lightening, etc. Similarly, it may remain confined to a smaller area occurring within a few seconds like hailstorms, tornadoes and dust storms, and it can also have global dimensions such as global warming and depletion of the ozone layer. Besides these, changes have different meanings for different people. It depends upon the perspective one takes while trying to understand them. From the perspective of nature, changes are value-neutral (these are neither good nor bad). But from the human perspective, these are value-loaded. There are some changes that are desirable and good like

the change of seasons, ripening of fruits, while there are others like earthquakes, floods and wars that are considered bad and undesirable. Observe the environment you live in and prepare a list of changes, which take place over a long period of time and those, which take place within a short period of time. Do you know why some changes are considered good and others bad? Prepare a list of changes, which you notice in your daily life and give reasons why some of these are considered good and others bad.

In this chapter, we will read about some of these changes, which are considered bad and have haunted humankind for a long time. Disasters in general and natural disasters in particular, are some such changes that are always disliked and feared by humankind. What is a Disaster? “Disaster is an undesirable occurrence resulting from forces that are largely outside human control, strikes quickly with little or no warning, which causes or threatens serious disruption of life and property including death and injury to a large number of people, and requires therefore, mobilisation of efforts in excess of that which are normally provided by statutory emergency services”.

For a long time, geographical literature viewed disasters as a consequence of natural forces; and human beings were treated as innocent and helpless victims in front of the mighty forces of nature. But natural forces are

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not the only causes of disasters. Disasters are also caused by some human activities. There are some activities carried by human beings that are directly responsible for disasters. Bhopal Gas tragedy, Chernobyl nuclear disaster, wars, release of CFCs (Chlorofluorocarbons) and increase of green house gases, environmental pollutions like noise, air, water and soil are some of the disasters which are caused directly by human actions. There are some other activities of human beings that accelerate or intensify disasters indirectly. Landslides and floods due to deforestation, unscientific land use and construction activities in fragile areas are some of the disasters that are the results of indirect human actions. Can you identify some other human activities going on in and around your neighbourhood and schools that can lead to disasters in the near future? Can you suggest some measures to prevent it? It is a common experience that human-made disasters have increased both in their numbers and magnitudes over the years and concerted efforts are on at various levels to prevent and minimise their occurrences. Though the success has been only nominal so far, it is possible to prevent some of these disasters created by human actions. As opposed to this, very little is possible to prevent natural disasters; therefore, the best way out is to emphasise on natural disaster mitigation and management. Establishment of National Institute of Disaster Management, India, Earth Summit at Rio de Janeiro, Brazil, 1993 and the World Conference on Disaster Management in May 1994 at Yokohama, Japan, etc. are some of the concrete steps towards this direction initiated at different levels. Most often it is observed that scholars use disasters and natural hazards as interchangeable. Both are related phenomena, yet quite distinct from each other. Hence, it is necessary to distinguish between the two. Natural Hazards are elements of circumstances in the Natural environment that have the potential to cause harm to people or property or both. These may be swift or permanent aspects of the respective environmental settings like currents in the oceans, steep slope and unstable structural

INDIA : PHYSICAL ENVIRONMENT

features in the Himalayas or extreme climatic conditions in deserts or glaciated areas. As compared to natural hazards, natural disasters are relatively sudden and cause large scale, widespread death, loss of property and disturbance to social systems and life over which people have a little or no control. Thus, any event can be classed as disaster when the magnitude of destruction and damage caused by it is very high. Generally, disasters are generalised experiences of people the world over, and no two disasters are similar and comparable to each other. Every disaster is unique in terms of the local socio-environmental factors that control it, the social response it generates, and the way each social group negotiates with it. However, the opinion mentioned above is indicative of three important things. Firstly, the magnitude, intensity, frequency and damages caused by natural disasters have increased over the years. Secondly, there is a growing concern among people the world over to deal with the menace created by these so that the loss of human life and property can be minimised. And finally, significant changes have taken place in the pattern of natural disasters over the years. There has also been a change in the perception of natural disasters and hazards. Previously, hazards and disasters were seen as two closely associated and interrelated phenomena, i.e. areas prone to natural hazards, were more vulnerable to disasters. Hence, people avoided tampering with the delicate balance that existed in a given ecosystem. People avoided intensification of their activities in such areas and that is how disasters were less damaging. Technological power has given large capacity to human intervention in nature. Consequently, now, human beings tend to intensify their activities into disaster prone areas increasing their vulnerability to disasters. Colonisation of flood plains of most of the rivers and development of large cities and port-towns like – Mumbai and Chennai along the coast, and touching the shore due to high land values, make them vulnerable to the occurrence of cyclones, hurricanes and tsunamis.

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These observations can also be corroborated by the data given in Table 7.1 showing the magnitude of deaths caused by twelve serious natural disasters in the past sixty years in different countries of the world. It is evident from the table that natural disasters have caused widespread loss of life and property. Concerted efforts are on at various levels to take appropriate measures to deal with the situation. It is also being felt that the damages caused by natural disasters have global repercussions that are beyond the means and capabilities of individual nation-states to cope up with. Hence, this issue was raised at the U.N. General Assembly in 1989 and it was finally formalised at the World Conference on Disaster Management in May 1994 at Yokohama, Japan. This was subsequently called the Yokohama Strategy and Plan of Action for a Safer World.

CLASSIFICATION

OF

NATURAL DISASTERS

Human beings the world over have experienced disasters and have faced and lived with them. Now people are becoming aware and various steps have been initiated at different levels for mitigating the effects of disasters. Identification and classification of disasters is being considered as an effective and scientific step to deal promptly and efficiently with the disasters. Broadly, natural disasters can be classified under four categories (See Table 7.2). India is one of those countries which has experienced most of the natural disasters mentioned in Table 7.2. Every year it loses thousands of lives and property worth millions of rupees due to these natural calamities. In the following section, some of

Table 7.1 : Top Twelve Natural Disasters Since 1948 Year

Location

Type

1948 1949 1954 1965 1968 1970 1970 1971 1976 1990 2004

The Soviet Union (now Russia) China China East Pakistan (now Bangladesh) Iran Peru East Pakistan (now Bangladesh) India China Iran Indonesia, Sri Lanka, India, etc.

Earthquakes Floods Floods Tropical Cyclones Earthquakes Earthquakes Tropical Cyclones Tropical Cyclones Earthquakes Earthquakes Tsunamis

2005

Pakistan, India

Earthquakes

Deaths 110,000 57,000 30,000 36,000 30,000 66,794 500,000 30,000 700,000 50,000 500,000* 70,000*

Source : United Nations Environmental Programme (UNEP), 1991 *News Report from National Institute for Disaster Management, Government of India, New Delhi

Table 7.2 : Classification of Natural Disasters Atmospheric

Terrestrial

Blizzards Thunderstorms Lightning Tornadoes Tropical Cyclone Drought Hailstorm Frost, Heat Wave or Loo.Cold Waves, etc.

Earthquakes Volcanic Eruptions Landslides Avalanches Subsidence Soil Erosion

Aquatic Floods Tidal Waves Ocean Currents Storm Surge Tsunami

Biological Plants and Animals as colonisers (Locusts, etc.). Insects infestation— fungal, bacterial and viral diseases such as bird flu, dengue, etc.

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Yokohama Strategy and International Decade for Natural Disaster Reduction (IDNDR) Yokohama Strategy and Plan of Action for a Safer World All the member states of the United Nations and other states met at the World Conference on Natural Disaster Reduction in the city of Yokohama from May 23rd-27th 1994. It acknowledged that the impact of natural disasters in terms of human and economic losses has risen in recent years, and society, in general, has become vulnerable to natural disasters. It also accepted that these disasters affected the poor and disadvantageous groups the worst, particularly in the developing countries, which are ill-equipped to cope with them. Hence, the conference adopted the Yokohama strategy as a guide to rest of the decade and beyond, to mitigate the losses due to these disasters. The resolution of the World Conference on Natural Disasters Reduction is as mentioned below: (i) It will note that each country has the sovereign responsibility to protect its citizens from natural disasters; (ii) It will give priority attention to the developing countries, particularly the least developed, land-locked countries and small-island developing states; (iii) It will develop and strengthen national capacities and capabilities and, where appropriate, national legislation for natural and other disaster prevention, mitigation and preparedness, including the mobilisation of non-governmental organisations and participation of local communities; (iv) It will promote and strengthen sub-regional, regional and international cooperation in activities to prevent, reduce and mitigate natural and other disasters, with particular emphasis on: (a) human and institutional capacity-building and strengthening; (b) technology sharing: the collection, the dissemination and utilisation of information; and (c) mobilisation of resources. It also declared the decade 1990-2000 as the International Decade for Natural Disaster Reduction (IDNDR).

the highly devastating natural disasters have been discussed, particularly in the context of India.

NATURAL DISASTERS

AND

HAZARDS

IN

INDIA

It was discussed in one of the previous chapters that India is vast and diverse in terms of its physical and socio-cultural attributes. It is largely due to its vast geographical area, environmental diversities and cultural pluralities that scholars often described it using two meaningful adjectives like the ‘Indian-subcontinent’ and the ‘land of unity in diversity’. Its vastness in terms of natural attributes combined with its prolonged colonial past, continuing various forms of social discriminations and also equally large population have enhanced its vulnerability to natural disasters. These observations can also be illustrated by focussing on some of the major natural disasters in India. Earthquakes Earthquakes are by far the most unpredictable and highly destructive of all the natural disasters. You have already learnt the causes

of earthquakes in your book Fundamentals of Physical Geography (NCER T, 2006). Earthquakes that are of tectonic origin have proved to be the most devastating and their area of influence is also quite large. These earthquakes result from a series of earth movements brought about by a sudden release of energy during the tectonic activities in the earth’s crust. As compared to these, the earthquakes associated with volcanic eruption, rock fall, landslides, subsidence, particularly in the mining areas, impounding of dams and reservoirs, etc. have limited area of influence and the scale of damage. It was mentioned in Chapter 2 of the book that the Indian plate is moving at a speed of one centimetre per year towards the north and northeastern direction and this movement of plates is being constantly obstructed by the Eurasian plate from the north. As a result of this, both the plates are said to be locked with each other resulting in accumulation of energy at different points of time. Excessive accumulation of energy results in building up of stress, which ultimately leads to the breaking up of the lock and the sudden release of energy causes

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earthquakes along the Himalayan arch. Some of the most vulnerable states are Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Sikkim, and the Darjiling and subdivision of West Bengal and all the seven states of the northeast.

Figure 7.1 : A Damaged Building Due to an Earthquake

Apart from these regions, the central-western parts of India, particularly Gujarat (in 1819, 1956 and 2001) and Maharashtra (in 1967 and 1993) have also experienced some severe earthquakes. Earth scientists have found it difficult to explain the occurrence of earthquakes in one of the oldest, most stable and mature landmass of Peninsular block for a long time. Recently, some earth scientists have come up with a theory of emergence of a fault line and energy build-up along the fault line represented by the river Bhima (Krishna) near Latur and Osmanabad (Maharashtra) and the possible breaking down of the Indian plate (Figure 7.2). National Geophysical Laboratory, Geological Survey of India, Department of Meteorology, Government of India, along with the recently formed National Institute of Disaster Management, have made an intensive analysis of more than 1,200 earthquakes that have occurred in India in different years in the past, and based on these, they divided India into the following five earthquake zones: (i) (ii) (iii) (iv) (v)

Very high damage risk zone High damage risk zone Moderate damage risk zone Low damage risk zone Very low damage risk zone.

Out of these, the first two zones had experienced some of the most devastating earthquakes in India. As shown in the Figure 7.2,

areas vulnerable to these earthquakes are the North-east states, areas to the north of Darbhanga and Araria along the Indo-Nepal border in Bihar, Uttaranchal, Western Himachal Pradesh (around Dharamshala) and Kashmir Valley in the Himalayan region and the Kuchchh (Gujarat). These are included in the Very High Damage Risk Zone. Similarly, the remaining parts of Jammu and Kashmir, Himachal Pradesh, Northern parts of Punjab, Eastern parts of Haryana, Delhi, Western Uttar Pradesh, and Northern Bihar fall under the High Damage Risk Zone. Remaining parts of the country fall under moderate to very Low Damage Risk Zone. Most of the areas that can be considered safe are from the stable landmass covered under the Deccan plateau. Socio-Environmental Earthquakes

Consequences

of

The idea of an earthquake is often associated with fear and horror due to the scale, magnitude and suddenness at which it spreads disasters on the surface of the earth without discrimination. It becomes a calamity when it strikes the areas of high density of population. It not only damages and destroys the settlements, infrastructure, transport and communication network, industries and other developmental activities but also robs the population of their material and socio-cultural gains that they have preserved over generations. It renders them homeless, which puts an extra-pressure and stress, particularly on the weak economy of the developing countries. Effects of Earthquakes Earthquakes have all encompassing disastrous effects on the area of their occurrence. Some of the important ones are listed in Table 7.3. Table 7.3 : Effects of Earthquakes On Ground

On Manmade Structures

Fissures Settlements

Cracking Slidings

Landslides Liquefaction Earth Pressure Possible Chain-effects

Overturning Buckling Collapse Possible Chain-effects

On Water Waves Hydro-Dynamic Pressure Tsunami

Possible Chain-effects

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Figure 7.2 : India: Earthquake Hazard Zones

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NATURAL HAZARDS AND DISASTERS

Apart from these, earthquakes also have some serious and far-reaching environmental consequences. Surface seismic waves produce fissures on the upper layers of the earth’s crust through which water and other volatile materials gush out, inundating the neighbouring areas. Earthquakes are also responsible for landslides and often these cause obstructions in the flow of rivers and channels resulting in the formation of reservoirs. Sometimes, rivers also change their course causing floods and other calamities in the affected areas. Earthquake Hazard Mitigation Unlike other disasters, the damages caused by earthquakes are more devastating. Since it also destroys most of the transport and communication links, providing timely relief to the victims becomes difficult. It is not possible to prevent the occurrence of an earthquake; hence, the next best option is to emphasis on disaster preparedness and mitigation rather than curative measures such as: (i) Establishing earthquake monitoring centres (seismological centres) for regular monitoring and fast dissemination of information among the people in the vulnerable areas. Use of Geographical Positioning System (GPS) can be of great help in monitoring the movement of tectonic plates. (ii) Preparing a vulnerability map of the country and dissemination of vulnerability risk information among the people and educating them about the ways and means minimising the adverse impacts of disasters. (iii) Modifying the house types and buildingdesigns in the vulnerable areas and discouraging construction of high-rise buildings, large industrial establishments and big urban centres in such areas. (iv) Finally, making it mandatory to adopt earthquake-resistant designs and use light materials in major construction activities in the vulnerable areas.

Tsunami Earthquakes and volcanic eruptions that cause the sea-floor to move abruptly resulting in sudden displacement of ocean water in the form of high vertical waves are called tsunamis (harbour waves) or seismic sea waves. Normally, the seismic waves cause only one instantaneous vertical wave; but, after the initial disturbance, a series of afterwaves are created in the water that oscillate between high crest and low trough in order to restore the water level. The speed of wave in the ocean depends upon the depth of water. It is more in the shallow water than in the ocean deep. As a result of this, the impact of tsunami is less over the ocean and more near the coast where they cause large-scale devastations. Therefore, a ship at sea is not much affected by tsunami and it is difficult to detect a tsunami in the deeper parts of sea. It is so because over deep water the tsunami has very long wave-length and limited wave-height. Thus, a tsunami wave raises the ship only a metre or two and each rise and fall takes several minutes. As opposed to this, when a tsunami enters shallow water, its wave-length gets reduced and the period remains unchanged, which increases the waveheight. Sometimes, this height can be up to 15m or more, which causes large-scale destructions along the shores. Thus, these are also called Shallow Water Waves. Tsunamis are frequently observed along the Pacific ring of fire, particularly along the coast of Alaska, Japan, Philippines, and other islands of Southeast Asia, Indonesia, Malaysia, Myanmar, Sri Lanka, and India etc. After reaching the coast, the tsunami waves release enormous energy stored in them and water flows turbulently onto the land destroying port-cities and towns, structures, buildings and other settlements. Since the coastal areas are densely populated the world over, and these are also centres of intense human activity, the loss of life and property is likely to be much higher by a tsunami as compared to other natural hazards in the coastal areas. The extent of devastation caused by tsunami can be assessed through the

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visuals on Banda Ache (Indonesia) presented in the book Practical Work in Geography - Part I (NCERT, 2006). Unlike other natural hazards, the mitigation of hazards created by tsunami is difficult, mainly because of the fact that losses are on a much larger scale.

(i) Large and continuous supply of warm and moist air that can release enormous latent heat. (ii) Strong Coriolis force that can prevent filling of low pressure at the centre (absence of Coriolis force near the equator prohibits the formation of t r o p i c a l c y c l o n e b e t w e e n 0 ° -5 ° latitude). (iii) Unstable condition through the troposphere that creates local disturbances around which a cyclone develops. (iv) Finally, absence of strong vertical wind wedge, which disturbs the vertical transport of latent heat. Structure of Tropical Cyclone

Figure 7.3 : Tsunami Affected Area

It is beyond the capacity of individual state or government to mitigate the damage. Hence, combined efforts at the international levels are the possible ways of dealing with these disasters as has been in the case of the tsunami that occurred on 26th December 2004 in which more than 300,000 people lost their lives. India has volunteered to join the International Tsunami Warning System after the December 2004 tsunami disaster. Tropical Cyclone Tropical cyclones are intense low-pressure areas confined to the area lying between 30° N and 30° S latitudes, in the atmosphere around which high velocity winds blow. Horizontally, it extends up to 500-1,000 km and vertically from surface to 12-14 km. A tropical cyclone or hurricane is like a heat engine that is energised by the release of latent heat on account of the condensation of moisture that the wind gathers after moving over the oceans and seas. There are differences of opinion among scientists about the exact mechanism of a tropical cyclone. However, some initial conditions for the emergence of a tropical cyclone are:

Tropical cyclones are characterised by large pressure gradients. The centre of the cyclone is mostly a warm and low-pressure, cloudless core known as eye of the storm. Generally, the isobars are closely placed to each other showing high-pressure gradients. Normally, it varies between 14-17mb/100 km, but sometimes it can be as high as 60mb/100km. Expansion of the wind belt is about 10-150 km from the centre. Spatio-temporal Distribution of T ropical Cyclone in India Owing to its Peninsular shape surrounded by the Bay of Bengal in the east and the Arabian Sea in the west, the tropical cyclones in India also originate in these two important locations. Though most of the cyclones originate between 10°-15° north latitudes during the monsoon season, yet in case of the Bay of Bengal, cyclones mostly develop during the months of O c t o b e r a n d N o v e m b e r. H e r e , t h e y originate between 16°-2° N latitudes and to the west of 92° E. By July the place of origin of these storms shifts to around 18° N latitude and west of 90°E near the Sunderban Delta. Table 7.4 and Figure 7.4 show the frequency and tracks of time of cyclonic storms in India.

NATURAL HAZARDS AND DISASTERS

Figure 7.4 : Tropical Cyclone Hazard Zones

85

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Table 7.4 : Frequency of Cyclonic Storms in India Months January February March April May June July August September October November December Total

Bay of Bengal Sea 4 (1.3) ∗ 1 (0.3) 4 (1.30) 18 (5.7) 28 (8.9) 34 (10.8) 38 (12.1) 25 (8.0) 27 (8.6) 53 (16.9) 56 (17.8) 26 (8.3) 314 (100)

Arabian 2 (2.4) 0 (0.0) 0 (0.0) 5 (6.1) 13 (15.9) 13 (15.9) 3 (3.7) 1 (1.2) 4 (4.8) 17 (20.7) 21 (25.6) 3 (3.7) 82 (100)

*Data in the brackets are in percentage to total number of storms taking place in a year

Consequences of Tropical Cyclones It was mentioned that the energy to the tropical cyclone comes from the latent heat released by the warm moist air. Hence, with the increase in distance from the sea, the force of the cyclone decreases. In India, the force of the cyclone decreases with increase in distance from the Bay of Bengal and the Arabian Sea. So, the coastal areas are often struck by severe cyclonic storms with an average velocity of 180 km/h. Often, this results in abnormal rise in the sea level known as Storm Surge. A surge is generated due to interaction of air, sea and land. The cyclone provides the driving force in the form of very high horizontal pressure-gradient and very strong surface winds. The sea water flows across the coast along with strong winds and heavy downpour.

disasters, the causes of floods are wellestablished. Floods are relatively slow in occurrences and often, occur in well-identified regions and within expected time in a year. Floods occur commonly when water in the form of surface run-off exceeds the carrying capacity of the river channels and streams and flows into the neighbouring low-lying flood plains. At times, this even goes beyond the capacity of lakes and other inland water bodies in which they flow. Floods can also be caused due to a storm surge (in the coastal areas), high intensity rainfall for a considerably longer time period, melting of ice and snow, reduction in the infiltration rate and presence of eroded material in the water due to higher rate of soil erosion. Though floods occur frequently over wide geographical area having disasterous ramifications in many parts of the world, floods in the South, Southeast and East Asian countries, particularly in China, India and Bangladesh, are frequent and equally disastrous. Once again, unlike other natural disasters, human beings play an important role in the genesis as well as spread of floods. Indiscriminate deforestation, unscientific agricultural practices, disturbances along the natural drainage channels and colonisation of flood-plains and river-beds are some of the human activities that play an important role in increasing the intensity, magnitude and gravity of floods.

This results in inundation of human settlements, agricultural fields, damaging crops and destruction of structures created by human beings. Floods You read in newspapers and watch images of floods on televisions occurring in some regions during rainy seasons. Inundation of land and human settlements by the rise of water in the channels and its spill-over presents the condition of flooding. Unlike other natural

Figure 7.5 : Brahmaputra During Flood

87

NATURAL HAZARDS AND DISASTERS

Figure 7.6 : Flood Hazard Zones

88

Various states of India face heavy loss of lives and property due to recurrent floods. Rashtriya Barh Ayog (National Flood Commission) identified 40 million hectares of land as flood-prone in India. The Figure 7.6 shows the flood-affected areas in India. Assam, West Bengal and Bihar are among the high flood-prone states of India. Apart from these, most of the rivers in the northern states like Punjab and Uttar Pradesh, are also vulnerable to occasional floods. It has been noticed that states like Rajasthan, Gujarat, Haryana and Punjab are also getting inundated in recent decades due to flash floods. This is partly because of the pattern of the monsoon and partly because of blocking of most of the streams and river channels by human activities. Sometimes, Tamil Nadu experiences flooding during November January due to the retreating monsoon. Consequence and Control of Floods Frequent inundation of agricultural land and human settlement, particularly in Assam, West Bengal, Bihar and Eastern Uttar Pradesh (flooding rivers), coastal areas of Orissa, Andhra Pradesh, Tamil Nadu and Gujarat (cyclone) and Punjab, Rajasthan, Northern Gujarat and Haryana (flash floods) have serious consequences on the national economy and society. Floods do not only destroy valuable crops every year but these also damage physical infrastructure such as roads, rails, bridges and human settlements. Millions of people are rendered homeless and are also washed down along with their cattle in the floods. Spread of diseases like cholera, gastro-enteritis, hepatitis and other water-borne diseases spread in the flood-affected areas. However, floods also make a few positive contributions. Every year, floods deposit fertile silt over agricultural fields which is good for the crops. Majuli (Assam), the largest riverine island in the world, is the best example of good paddy crops after the annual floods in Brahmaputra. But these are insignificant benefits in comparison to the grave losses. The Government of India as well as the state governments are well aware of the menace created by floods every year. How do these

INDIA : PHYSICAL ENVIRONMENT

governments generally respond to the floods? Construction of flood protection embankments in the flood-prone areas, construction of dams, afforestation and discouraging major construction activities in the upper reaches of most of the flood-creating rivers, etc. are some steps that need to be taken up on urgent basis. Removal of human encroachment from the river channels and depopulating the flood plains can be the other steps. This is particularly true in western and northern parts of the country which experience flash-floods. Cyclone centres may provide relief in coastal areas which are hit by a storm surge. Droughts The term ‘drought’ is applied to an extended period when there is a shortage of water availability due to inadequate precipitation, excessive rate of evaporation and over-utilisation of water from the reservoirs and other storages, including the ground water. Drought is a complex phenomenon as it involves elements of meteorology like precipitation, evaporation, evapotranspiration, ground water, soil moisture, storage and surface run-off, agricultural practices, particularly the types of crops grown, socio-economic practices and ecological conditions.

Types of Droughts Meteorological Drought : It is a situation when there is a prolonged period of inadequate rainfall marked with mal-distribution of the same over time and space. Agricultural Drought : It is also known as soil moisture drought, characterised by low soil moisture that is necessary to support the crops, thereby resulting in crop failures. Moreover, if an area has more than 30 per cent of its gross cropped area under irrigation, the area is excluded from the drought-prone category. Hydrological Drought : It results when the availability of water in different storages and reservoirs like aquifers, lakes, reservoirs, etc. falls below what the precipitation can replenish.

89

NATURAL HAZARDS AND DISASTERS

Figure 7.8 : Drought Prone Areas

90

INDIA : PHYSICAL ENVIRONMENT

Extreme Drought Affected Areas : It is evident from the Figure 7.8 that most parts of Rajasthan, particularly areas to the west of the Aravali hills, i.e. Marusthali and Kachchh regions of Gujarat fall in this category. Included here are also the districts like Jaisalmer and Barmer from the Indian desert that receive less that 90 mm average annual rainfall.

Figure 7.7 : Drought

Ecological Drought : When the productivity of a natural ecosystem fails due to shortage of water and as a consequence of ecological distress, damages are induced in the ecosystem. Various parts of India experience these droughts recurrently which result in some serious socio-economic and ecological problems. Drought Prone Areas in India Indian agriculture has been heavily dependent on the monsoon rainfall. Droughts and floods are the two accompanying features of Indian climate. According to some estimates, nearly 19 per cent of the total geographical area of the country and 12 per cent of its total population suffer due to drought every year. About 30 per cent of the country’s total area is identified as drought prone affecting around 50 million people. It is a common experience that while some parts of the country reel under floods, there are regions that face severe drought during the same period. Moreover, it is also a common sight to witness that one region suffers due to floods in one season and experiences drought in the other. This is mainly because of the large-scale variations and unpredictability in the behaviour of the monsoon in India. Thus, droughts are widespread and common phenomena in most parts of the country, but these are most recurrent and severe in some and not so in others. On the basis of severity of droughts, India can be divided into the following regions:

Severe Drought Prone Area : Parts of eastern Rajasthan, most parts of Madhya Pradesh, eastern parts of Maharashtra, interior parts of Andhra Pradesh and Karnataka Plateau, northern parts of interior Tamil Nadu and southern parts of Jharkhand and interior Orissa are included in this category. Moderate Drought Affected Area : Northern parts of Rajasthan, Haryana, southern districts of Uttar Pradesh, the remaining parts of Gujarat, Maharashtra except Konkan, Jharkhand and Coimbatore plateau of Tamil Nadu and interior Karnataka are included in this category. The remaining parts of India can be considered either free or less prone to the drought. Consequences of Drought Droughts have cascading effects on various other aspects of environment and society. Crop failure leading to scarcity of food grains (akal), fodder (trinkal), inadequate rainfall, resulting in shortage of water (jalkal), and often shortage in all the three (trikal) is most devastating. Large-scale death of cattle and other animals, migration of humans and livestock are the most common sight to be seen in the droughtaffected areas. Scarcity of water compels people to consume contaminated water resulting in spread of many waterborne diseases like gastro-enteritis, cholera, hepatitis, etc. Droughts have both immediate as well as long-term disastrous consequences on the social and physical environments. Consequently, planning for drought has to take both aspects into consideration. Provision for the distribution of safe drinking water, medicines for the victims and availability of fodder and water for the cattle and shifting of the people and their livestock

91

NATURAL HAZARDS AND DISASTERS

to safer places, etc. are some steps that need to be taken immediately. Identification of ground water potential in the form of aquifers, transfer of river water from the surplus to the deficit areas, and particularly planning for inter-linking of rivers and construction of reservoirs and dams, etc. should be given a serious thought. Remote sensing and satellite imageries can be useful in identifying the possible river-basins that can be inter-linked and in identifying the ground water potential. Dissemination of knowledge about drought-resistant crops and proper training to practise the same can be some of the long-term measures that will be helpful in drought-mitigation. Rainwater harvesting can also be an effective method in minimising the effects of drought. Observe the methods adopted for rooftop rainwater harvesting in your locality and suggest measures to make it more effective.

Landslides Have you ever read about the blocking of roads to Srinagar or disruption of rail services by stones falling on the Konkan Railway track? It happens due to landslide, which is the rapid sliding of large mass of bedrocks. Disasters due to landslides, are in general, far less dramatic than due to earthquakes, volcanic eruptions, tsunamis and cyclones but their impact on the natural environment and national economy is in no way less severe. Unlike other disasters that are sudden, unpredictable and are largely controlled by macro or regional factors, landslides are largely controlled by highly localised factors. Hence, gathering information and monitoring the possibilities of landslide is not only difficult but also immensely cost-intensive. It is always difficult to define in a precise statement and generalise the occurrence and behaviour of a landslide. However, on the basis of past experiences, frequency and certain causal relationships with the controlling factors like geology, geomorphic agents, slope, land-use, vegetation cover and

human activities, India has been divided into a number of zones. Landslide Vulnerability Zones Very High Vulnerability Zone : Highly unstable, relatively young mountainous areas in the Himalayas and Andaman and Nicobar, high rainfall regions with steep slopes in the Western Ghats and Nilgiris, the north-eastern regions, along with areas that experience frequent ground-shaking due to earthquakes, etc. and areas of intense human activities, particularly those related to construction of roads, dams, etc. are included in this zone. High Vulnerability Zone : Areas that have almost similar conditions to those included in the very high vulnerability zone are also included in this category. The only difference between these two is the combination, intensity and frequency of the controlling factors. All the Himalayan states and the states from the north-eastern regions except the plains of Assam are included in the high vulnerability zones. Moderate to Low Vulnerability Zone : Areas that receive less precipitation such as TransHimalayan areas of Ladakh and Spiti (Himachal Pradesh), undulated yet stable relief and low precipitation areas in the Aravali, rain shadow areas in the Western and Eastern Ghats and Deccan plateau also experience occasional landslides. Landslides due to mining and

Figure 7.9 : Landslide

92

subsidence are most common in states like Jharkhand, Orissa, Chhattisgarh, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, Tamil Nadu, Goa and Kerala. Other Areas : The remaining parts of India, particularly states like Rajasthan, Haryana, Uttar Pradesh, Bihar, West Bengal (except district Darjiling), Assam (except district Karbi Anglong) and Coastal regions of the southern States are safe as far as landslides are concerned. Consequences of Landslides Landslides have relatively small and localised area of direct influence, but roadblock, destruction of railway lines and channelblocking due to rock-falls have far-reaching consequences. Diversion of river courses due to landslides can also lead to flood and loss of life and property. It also makes spatial interaction difficult, risky as well as a costly affair, which, in turn, adversely affects the developmental activities in these areas. Mitigation It is always advisable to adopt area-specific measures to deal with landslides. Restriction on the construction and other developmental activities such as roads and dams, limiting agriculture to valleys and areas with moderate slopes, and control on the development of large settlements in the high vulnerability zones, should be enforced. This should be supplemented by some positive actions like promoting large-scale afforestation programmes and construction of bunds to reduce the flow of water. Terrace farming should be encouraged in the northeastern hill states where Jhumming (Slash and Burn/Shifting Cultivation) is still prevalent.

DISASTER MANAGEMENT Disasters due to cyclones, unlike the ones caused by earthquakes, tsunamis and volcanic eruptions are more predictable in terms of the time and place of their occurrences. Moreover, with the help of development of techniques to monitor the behaviour of cyclones, their intensity, direction and magnitude, it has become possible to manage the cyclonic hazard

INDIA : PHYSICAL ENVIRONMENT

to some extent. Construction of cycloneshelters, embankments, dykes, reservoirs and afforestation to reduce the speed of the winds are some of the steps that can help in minimising the damages. However, increase in the loss of life and property in countries like India, Bangladesh, Myanmar, etc. in successive storms is largely due to high vulnerability of their population residing in the coastal areas. Disaster Management Bill, 2005 The Disaster Management Bill, 2005, defines disaster as a catastrophe, mishap, calamity or grave occurrence affecting any area, arising from natural or man-made causes, or by accident or negligence which results in substantial loss of life or human suffering or damage to, and destruction of, environment, and is of such nature or magnitude as to be beyond the coping capacity of the community of the affected area.

CONCLUSION On the basis of the above discussion, it can be concluded that disasters can be natural or the results of human activities, and all hazards need not turn into disasters since it is difficult to eliminate disasters, particularly natural disasters. Then the next best option is mitigation and preparedness. There are three stages involved in disaster mitigation and management: (i) Pre-disaster management involves generating data and information about the disasters, preparing vulnerability zoning maps and spreading awareness among the people about these. Apart from these, disaster planning, preparedness and preventive measures are other steps that need to be taken in the vulnerable areas. (ii) During disasters, rescue and relief operations such as evacuation, construction of shelters and relief camps, supplying of water, food, clothing and medical aids etc. should be done on an emergency basis. (iii) Post-disaster operations should involve rehabilitation and recovery of victims. It

93

NATURAL HAZARDS AND DISASTERS

should also concentrate on capacitybuilding in order to cope up with future disasters, if any. These measures have special significance to a country like India, which has about two-third of its geographical area and equal

proportion of its population, vulnerable to disasters. Introduction of the Disaster Management Bill, 2005 and establishment of National Institute of Disaster Management are some examples of the positive steps taken by the Government of India.

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i)

Which one of the following states of India experiences floods frequently? (a) Bihar (c) Assam (b) West Bengal (d) Uttar Pradesh

(ii) In which one of the following districts of Uttaranchal did Malpa Landslide disaster take place? (a) Bageshwar (b) Champawat

(c) Almora (d) Pithoragarh

(iii) Which one of the following states receives floods in the winter months? (a) Assam (b) West Bengal

(c) Kerala (d) Tamil Nadu

(iv) In which of the following rivers is the Majuli River Island situated? (a) Ganga (c) Godavari (b) Brahmaputra (d) Indus (v) Under which type of natural hazards do blizzards come? (a) Atmospheric (c) Terrestrial (b) Aquatic (d) Biological 2.

Answer the following questions in less than 30 words. (i) When can a hazard become a disaster? (ii) Why are there more earthquakes in the Himalayas and in the north-eastern region of India? (iii) What are the basic requirements for the formation of a cyclone? (vi) How are the floods in Eastern India different from the ones in Western India? (v) Why are there more droughts in Central and Western India?

3. Answer the following questions in not more than 125 words. (i) Identify the Landslide-prone regions of India and suggest some measures to mitigate the disasters caused by these. (ii) What is vulnerability? Divide India into natural disaster vulnerability zones based on droughts and suggest some mitigation measures. (v) When can developmental activities become the cause of disasters? Project/Activity Prepare a project report on any one of the topics given below. (i) Malpa Landslide (ii) Tsunami

(v) Tehri Dam/Sardar Sarovar (vi) Bhuj/Latur Earthquakes

(iii) Orissa and Gujarat Cyclones (vii) Life in a delta/riverine island (iv) Inter-linking of rivers

(viii) Prepare a model of rooftop rainwater harvesting

APPENDIX

STATES, THEIR CAPITALS, NUMBER OF DISTRICTS, AREA AND POPULATION Sl. No.

State

Capital

1.

Andhra Pradesh

Hyderabad

2.

Arunachal Pradesh

3.

Assam

4.

No. of Districts

Area in sq. km

Population

23

2,75,060

7,57,27,541

Itanagar

14

83,743

10,91,117

Dispur

23

78,438

2,66,38,407

Bihar

Patna

37

94,163

8,28,78,796

5.

Chhattisgarh

Raipur

16

1,36,034

2,07,95,956

6.

Goa

Panji

02

3,702

13,43,998

7.

Gujarat

Gandhi Nagar

25

1,96,024

5,05,96,992

8.

Haryana

Chandigarh

19

44,212

2,10,82,982

9.

Himachal Pradesh

Shimla

12

55,673

60,77,248

10.

Jammu and Kashmir

Srinagar

14

2,22,236

1,00,69,917

11.

Jharkhand

Ranchi

18

79,714

2,69,09,428 5,27,83,958

12.

Karnataka

Bangalore

27

1,91,791

13.

Kerala

Tiruvanantapuram

14

38,863

3,18,38,619

14.

Madhya Pradesh

Bhopal

45

3,08,000

6,03,85,118

15.

Maharashtra

Mumbai

35

3,07,713

9,67,52,247

16.

Manipur

Imphal

9

22,327

23,88,634

17.

Meghalaya

Shillong

7

22,327

23,06,069

18.

Mizoram

Aizawl

8

21,081

8,91,058

19.

Nagaland

Kohima

8

16,579

19,88,636

20.

Orissa

Bhubaneshwar

30

1,55,707

3,67,06,920

21.

Punjab

Chandigarh

17

50,362

2,42,89,296

22.

Rajasthan

Jaipur

32

3,42,239

5,64,73,122

23.

Sikkim

Gangtok

04

7,096

5,40,493

24.

Tamil Nadu

Chennai

29

1,30,058

6,21,10,839 31,91,168

25.

Tripura

Agartala

04

10,49,169

26.

Uttaranchal

Dehra Dun

13

53,484

84,79,562

27.

Uttar Pradesh

Lucknow

70

2,38,566

16,60,52,859

28.

West Bengal

Kolkata

18

88,752

8,02,21,171

APPENDIX

UNION TERRITORIES, THEIR CAPITALS, AREA AND POPULATION Sl. No.

Union Territories

Capital

Area

Population

1. 2. 3. 4. 5. 6. 7.

Andaman and Nicobar Islands Chandigarh Dadra and Nagar Haveli Daman and Diu NCT Delhi Lakshadweep Pondicherry

Port Blair Chandigarh Silvassa Daman * Delhi Kavaratti **Pondicherry

8,249 114 491 112 1483 32 492

3,56,152 9,00,914 2,20,490 1,58,204 1,38,00000 60,595 9,73,829

Note

: * Delhi has the status of National Capital Territory with a Legislative Assembly ** Pondicherry also has a Legislative Assembly Source : India-2005, A Reference Annual, Publications Division, Ministry of Information and Broadcasting

APPENDIX

IMPORTANT RIVER BASINS Rivers

Indus (in India) Ganga (in India) Brahmaputra (in India) Barak and others Flowing to Meghna Sabarmati Mahi Narmada Tapti Brahmani and Baitarni Mahanadi Godavari Krishna Penner Kaveri Suvarnarekha Total

Length (in km)

Catchment Area (sq. km) Potential Discharge in the River (km3)

Average Annual Flow Excluding the Groundwater (km3)

Estimated Utilisable

1,114 2,525 916

321,289 861,452 194,413 41,723

73.31 525.02

46.0 250.0

371 585 1,312 724 799+365 851 1,465 1,401 597 800 395

21,674 34,842 98,796 65,145 39,033+12,789 141,589 312,812 258,948 55,213 81,155 19,296

3.81 11.02 45.64 14.88 28.48 66.88 110.54 78.12 6.32 21.36 12.37

1.99 3.10 34.30 14.50 18.30 49.99 76.30 58.00 6.86 19.00 6.81

2,528,084

1,869.35

690.31

248,505

255.02

59.03

2,776,589

2,124.37

749.34

Medium river basins flowing

{ towards the east and west directions Total

APPENDIX

STATE/UNION TERRITORY WISE FOREST COVER State/UT

Andhra Pradesh

Geographic Area

Forest Cover Dense

Open

Total

Percent

275,069

25,827

18,810

44,637

16.23

Arunachal Pradesh

83,743

53,932

14,113

68,045

81.25

Assam

78,438

15,830

11,884

27,714

35.33

Bihar

94,163

3,372

2,348

5,720

6.07

135,191

37,880

18,568

56,448

41.75

1,483

38

73

111

7.51 56.59

Chhattisgarh Delhi Goa

3,702

1,785

310

2,095

196,022

8,673

6,479

15,152

7.73

Haryana

44,212

1,139

615

1,754

3.97

Himachal Pradesh

55,673

10,429

3,931

14,360

25.79

222,236

11,848

9,389

21,237

9.56

79,714

11,787

10,850

22,637

28.40

191,791

26,156

10,835

36,991

19.29

38,863

11,772

3,788

15,560

40.04

Madhya Pradesh

308,245

44,384

32,881

77,265

25.07

Maharashtra

307,713

30,894

16,588

47,482

15.43

Manipur

22,327

5,710

11,216

16,926

75.81

Meghalaya

22,429

5,681

9,903

15,584

69.48

Mizoram

21,081

8,936

8,558

17,494

82.98

Nagaland

16,579

5,393

7,952

13,345

80.49

Orissa

155,707

27,972

20,866

48,838

31.36

Punjab

50,362

1,549

883

2,432

4.83

342,239

6,322

10,045

16,367

4.78

7,096

2,391

802

3,193

45.00

130,058

12,499

8,983

21,482

16.52

10,486

3,463

3,602

7,065

67.38

Gujarat

Jammu & Kashmir Jharkhand Karnataka Kerala

Rajasthan Sikkim Tamilnadu Tripura Uttar Pradesh

240,928

8,965

4,781

13,746

5.71

Uttaranchal

53,483

19,023

4,915

23,938

44.76

West Bengal

88,752

6,346

4,347

10,693

12.05

8,249

6,593

337

6,930

84.01

Andaman & Nicobar Chandigarh

114

5

4

9

7.51

Dadra & Nagar Haveli

491

151

68

219

44.60

Daman & Diu

112

2

4

6

5.53

Lakshadweep

32

27

0

27

85.91

480

35

1

36

7.45

3,287,263

416,809

258,729

675,538

20.55

Pondicherry Total

Source : State Forest Report, 2001

APPENDIX

NATIONAL PARKS OF INDIA State/UT

Andhra Pradesh

Area of State

National Parks (km2)

Area Covered (km2)

% of State Area

275,068

4

373.23

0.14

Arunachal Pradesh

83,743

2

2290.82

2.74

Assam

78,438

5

1968.60

2.51

Bihar Chhattisgarh

94,163

1

335.65

0.36

135,194

3

2929.50

2.17

Goa

3,702

1

107.00

2.89

Gujarat

196,024

4

480.11

0.24

Haryana

442,122

2

117.13

0.26

55,673

2

1429.40

2.57

222,235

4

4680.25

2.11

Himachal Pradesh Jammu and Kashmir Jharkhand Karnataka Kerala

79,714

1

231.67

0.29

191,791

5

2435.14

1.27

38,863

4

549.34

1.41 1.19

Madhya Pradesh

308,252

9

3656.36

Maharashtra

307,690

5

955.93

0.31

Manipur

22,327

1

40.00

0.18

Meghalaya

22,429

2

267.48

1.19

Mizoram

21,081

2

250.00

1.19

Nagaland

16,579

1

202.02

1.22

155,707

2

990.70

0.64

Orissa Punjab Rajasthan

50,362

0

0.00

0.00

342,239

5

4122.33

1.20

7,096

1

1784.00

25.14

130,058

5

307.84

0.24

10,486

0

0.00

0.00

Sikkim Tamil Nadu Tripura

240,926

1

490.00

0.20

Uttaranchal

Uttar Pradesh

53,485

6

4725.00

7.62

West Bengal

88,752

5

1693.25

1.91

1156.91 0.00 0.00 0.00 0.00 0.00 0.00 38,569.66

14.02 0.00 0.00 0.00 0.00 0.00 0.00 1.17

Union Territories Andaman and Nicobar Chandigarh Dadra and Nagar Haveli Daman & Diu Delhi Lakshadweep Pondicherry India

8,249 114 491 112 1,483 32 493 3,287,263

Source: State Forest Report, 2001

9 0 0 0 0 0 0 92

G LOSSARY

Alluvial Plain : A level tract of land made up of alluvium or fine rock material brought down by a river. Archipelago : A group of islands that lie in fairly close proximity. Arid : Denoting any climate or region in which the rainfall is insufficient or barely sufficient to support vegetation. Backwater : A stretch of water that has become bypassed by the main flow of a stream, although still joined to it. It has a very low rate of flow. Bedrock : The solid rock lying beneath soil and weathered material. Biosphere Reserve : These are multi-purpose protected areas, where every plant and animal size is to be protected in its natural habitat. Its major objectives are : (i) to conserve and maintain diversity and integrity of the natural heritage in its full form, i.e. physical environment, the flora and the fauna; (ii) to promote research on ecological conservation and other aspects of environment at preservation; (iii) to provide facilities for education, awareness and explaining. Bunding : The practice of constructing embankments of earth or stone for conserving water and soil to increase crop production. Calcareous : Composed of or containing a high proportion of calcium carbonate. Catchment Area : The area drained by a major river and its tributaries. Climate : The average weather conditions of a sizeable area of the earth’s surface over a period of time (usually spread over a span of at least 30 years). Coast : The boundary between land and sea. It includes the strip of land that borders the sea shore. Coastal Plain : It is a flat low lying land between the coast and higher ground inland. Conservation : The protection of natural environment and natural resources for the future. It includes the management of minerals, landscape, soil and forests to prevent their destruction and over exploitation. Coral : It is a small calcium secreting marine polyp that occurs in colonies, mainly in warm shallow sea water. It forms the coral reefs. Depression : In meteorology; it denotes an area of relatively low atmospheric pressure, which is found mainly in temperate regions. It is also used as synonym for temperate cyclones. Estuary : The tidal mouth of a river where fresh and saline water get mixed. Fauna : The animal life of a given area or time. Fold : A bend in rock strata resulting from compression of an area of the earth’s crust. Glacier : A mass of snow and ice that moves slowly away from its place of accumulation carving gradually a broad and steepsided valley on its way. Gneiss : A coarse grained metamorphic rock with a banded structure. It is formed by the large scale application of heat and pressure associated with mountain building and volcanic activity. Gorge : A deep valley with steep and rocky side walls.

100

GLOSSARY

Gully Erosion : It is the erosion of the soil and rock by the concentration of runoff into gullies. Humus : The dead organic content of the soil. Island : A mass of land that is surrounded by water and is smaller than a continent. Jet Stream : A very strong and steady westerly wind blowing just below the tropopause. Lake : A body of water that lives in a hollow in the earth’s surface and is entirely surrounded by land. Landslide : A form of mass movement in which rock and debris moves rapidly downslope under the influence of gravity as a result of failure along a shear plane. Meander : A pronounced curve or loop in the course of a river channel. Monsoon : A complete reversal of winds over a large area leading to a change of seasons. National Park : A National park is an area which is strictly reserved for the protection of the wildlife and where activities such as forestry, grazing or cultivation are not allowed. Pass : A route through a mountain range which follows the line of a col or a gap. Peninsula : A piece of land jutting out into the sea. Plain : An extensive area of flat or gently undulating land. Plateau : An extensive elevated area of relatively flat land. Playa : The low flat central area of a basin of inland drainage. Playas occur in areas of low rainfall. Protected Forest : An area notified under the provisions of Indian Forest Act or the State Forest Acts having limited degree of protection. In Protected Forests, all activities are permitted unless prohibited. Rapids : A stretch of swift flowing water where a river bed suddenly becomes steeper due to the presence of hard rocks. Reserved Forest : An area notified under the provisions of Indian Forest Act or the State Forest Acts having full degree of protection. In Reserved Forests, all activities are prohibited unless permitted. Sanctuary : A sanctuary is an area, which is reserved for the conservation of animals only and operations such as harvesting of timber, collection of minor forest products are allowed so long as they do not affect the animals adversely. Soil Profile : It is the vertical section of soil from the ground surface to the parent rock. Subcontinent : A big geographical unit which stands out distinctly from the rest of the continent. Terai : A belt of marshy ground and vegetation on the lower parts of the alluvial fans. Tectonic : Forces originating within the earth and responsible for bringing widespread changes in the landform features. Unclassed Forest : An area recorded as forest but not included in reserved or protected forest category. Ownership status of such forests varies from state to state.

CONTENTS FOREWORD

v

CHAPTER 1 Introduction to Maps

1

CHAPTER 2 Map Scale

17

CHAPTER 3 Latitude, Longitude and Time

26

CHAPTER 4 Map Projections

35

CHAPTER 5 Topographical Maps

49

CHAPTER 6 Introduction To Aerial Photographs

69

CHAPTER 7 Introduction To Remote Sensing CHAPTER 8 Weather Instruments, Maps and Charts

84

107

Introduction to Maps

Chapter 1

Introduction to Maps You may be familiar with maps that you have seen in most of your books of social sciences representing the earth or any of its parts. You may also know that the shape of the earth is geoid (three-dimensional) and a globe can best represent it (Fig. 1.1). A map, on the other hand, is a simplified depiction of whole or part of the earth on a piece of paper. In other words, it is a two-dimensional form of

Figure 1.1 India as it is seen on the globe

the three-dimensional earth. Hence, a map can be drawn using a system of

map projections (see Chapter 4). As it is impossible to represent all features of the earth’s surface in their true size and form, a map is drawn at a reduced scale. Imagine your school campus. If a plan/map of your school is to be drawn in its actual size, it will be as large as the campus itself. Hence, maps are drawn at a scale and projection so that each point on the paper corresponds to the actual ground position. Besides, the representation of different features is also simplified using symbols, colours and shades. A map is, therefore, defined as selective, symbolised and generalised representation of whole or a

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2

Figure 1.2 Sketch of the Environs of Delhi (Left) and a Map of Delhi (Right)

Glossary Cadastral Map : A large-scale map drawn at a scale of 1 : 500 to 1 : 4000 to show property boundaries, designating each parcel of land with a number. Cardinal Points : North (N), South (S), East (E) and West (W). Cartography : Art, science and technology of making maps, charts, plans and other modes of graphical expression as well as their study and use. Generalisation-Map : A simplified representation of the features on the map, appropriate to its scale or purpose, without affecting their visual form. Geoid : An oblate spheroid whose shape resembles the actual shape of the Earth. Map : A selective, symbolised and generalised representation of the whole or part of the earth at a reduced scale. Map series : A group of maps produced at same scale, style and specifications for a country or a region. Projection-Map : The system of the transformation of the spherical surface onto a plane surface. Scale : The ratio between the distances of two points on the map, plan or photograph and the actual distance between the same two points on the ground. Sketch Map : A simplified map drawn freehand which fails to preserve the true scale or orientation.

Introduction to Maps

part of the earth's surface on a plane surface at a reduced scale. It may also be understood that a simple network of lines and polygons without a scale shall not be called a map. It is only referred to as “the sketch” (Fig. 1.2). In the present chapter, we will study the essential requirements of maps, their types and the uses.

ESSENTIALS

OF

MAP MAKING

In view of the variety of maps, we may find it difficult to summarise what they all have in common. Cartography, being an art and science of map-making, does include a series of processes that are common to all the maps. These processes that may also be referred to as essentials of maps are : “ “

Scale Map Projection

“

Map Generalisation

“

Map Design Map Construction and Production

“

Scale: We know that all maps are reductions. The first decision that a map-maker has to take is about the scale of the map. The choice of scale is of utmost importance. The scale of a map sets limits of information contents and the degree of reality with which it can be delineated on the map. For example, figure 1.3 provides a comparison between maps having different scales and the improvements made thereupon with the change in scale.

Projection: We also know that maps are a simplified representation of the three-dimensional surface of the earth on a plane sheet of paper. The transformation of all-side-curved-geoidal surface into a plane surface is another important aspect of the cartographic process. We should know that such a radical transformation introduces some unavoidable changes in directions, distances, areas and shapes from the way they appear on a geoid. A system of transformation of the spherical surface to the plane surface is called a map projection. Hence, the choice, utilisation and construction of projections is of prime importance in map-making.

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4

A Portion of Sheet NH 43

A Portion of Sheet 53 H/2

A Portion of Sheet 53 H

A Portion of Guide Map Figure 1.3 Effect of Scale on Mapped Information

Introduction to Maps

Generalisation: Every map is drawn with a definite objective. For example, a general purpose map is drawn to show information of a general nature such as relief, drainage, vegetation, settlements, means of transportation, etc. Similarly, a special purpose map exhibits information pertaining to one or more selected themes like population density, soil types or location of industries. It is, therefore, necessary to carefully plan the map contents while the purpose of the map must be kept in the forefront. As maps are drawn at a reduced scale to serve a definite purpose, the third task of a cartographer is to generalise the map contents. In doing so, a cartographer must select the information (data) relevant to the selected theme and simplify it as per the needs.

Map Design: The fourth important task of a cartographer is the map design. It involves the planning of graphic characteristics of maps including the selection of appropriate symbols, their size and form, style of lettering, specifying the width of lines, selection of colours and shades, arrangement of various elements of map design within a map and design for map legend. The map design is, therefore, a complex aspect of mapmaking and requires thorough understanding of the principles that govern the effectiveness of graphic communication.

Map Construction and Production: The drawing of maps and their reproduction is the fifth major task in the cartographic process. In earlier times, much of the map construction and reproduction work used to be carried out manually. Maps were drawn with pen and ink and printed mechanically. However, the map construction and reproduction has been revolutionalised with the addition of computer assisted mapping and photo-printing techniques in the recent past.

HISTORY

OF

MAP MAKING

The history of map making is as old as the history of mankind itself. The oldest map was found in Mesopotamia drawn on a clay tablet that belongs to 2,500 B.C. Figure 1.4 shows Ptolemy’s Map of the World. Greek and the Arab geographers laid the foundation of modern cartography. The measurement of the circumference of the Earth and the use of the system of geographical coordinates in map-making are some of the significant contributions of the Greeks and the Arabs. The art and science of map

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making was revitalised in early modern period, with extensive efforts made to minimise the

6

effects of the transformation of the geoid onto a plane surface. The maps were drawn on different projections to obtain true directions, correct distances and to measure area accurately. The aerial photography supplemented Figure 1.4 Ptolemy’s Map of the World

the ground method of survey and the uses of aerial photographs stimulated map-making in the nineteenth centuries.

and

twentieth

The foundation of map-making in India was laid during the Vedic period when the expressions of astronomical truths and cosmological revelations were made. The expressions were crystallised into ‘sidhantas' or laws in classical treaties of Arya Bhatta, Varahamihira and Bhaskara, and others. Ancient Indian scholars divided the known world into seven ‘dwipas’ (Fig. 1.5). Mahabharata conceived a round world surrounded by water (Fig. 1.6).

Todarmal pioneered land

Figure 1.5 Seven Dwipas of the World as conceived in Ancient India

Figure 1.6 Round World surrounded by water as conceived in Mahabharata

Introduction to Maps

surveying and map-making as an integral part of the revenue collection procedure. Besides, Sher Shah Suri’s revenue maps further enriched the mapping techniques during the medieval period. The intensive topographical surveys for the preparation of up–to–date maps of the entire country, were taken up with the setting up of the Survey of India in 1767, which culminated with the map of Hindustan in 1785. Today, the Survey of India produces maps at different scales for the entire country.

Types of Maps Based on Scale: On the basis of scale, maps may be classified into large-scale and small-scale. Large scale maps are drawn to show small areas at a relatively large-scale. For example, the topographical maps drawn at a scale of 1: 250,000, 1:50,000 or 1:25,000 and the village maps, the zonal plans of the cities and house plans prepared on a scale of 1:4,000, 1:2,000 and 1:500 are large scale maps. On the other hand, small-scale maps are drawn to show large areas. For example, atlas maps, wall maps, etc. (i) Large-scale Maps: Large-scale maps are further divided into the following types : (a) Cadastral maps (b) Topographical maps (a) Cadastral Maps : The term ‘cadastral’ is derived from the French word ‘cadastre’ meaning ‘register of territorial property’. These maps are drawn to show the ownership of landed property by demarcating field boundaries of agricultural land and the plan of individual houses in urban areas. The cadastral maps are prepared by the government agencies to realise revenue and taxes, along with keeping a record of ownership. These maps are drawn on a very large scale, such as the cadastral maps of villages at 1 : 4,000 scale and the city plans at a scale of 1 : 2,000 and larger. (b) Topographical Maps : These maps are also prepared on a fairly large scale. The topographical maps are based on precise surveys and are prepared in the form of series of maps made by the national mapping agencies of almost all countries of the world (Chapter 5). For example, the Survey of India undertakes the topographical mapping of the entire country at 1 : 250,000, 1 : 50,000 and 1 : 25,000 scale (Fig. 1.3). These maps follow uniform colours and symbols to show topographic details such as relief, drainage, agricultural land, forest, settlements, means of

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communication, location of schools, post offices and other services and

8

facilities. (ii) Small-scale Maps: Small-scale maps are further divided into the following types : (a) Wall Maps (b) Atlas Maps (a) Wall Maps : These maps are generally drawn on large size paper or on plastic base for use in classrooms or lecture halls. The scale of wall maps is generally smaller than the scale of topographical maps but larger than atlas maps. (b) Atlas Maps : Atlas maps are very small-scale maps. These maps represent fairly large areas and present highly generalised picture of the physical or cultural features. Even so, an atlas map serves as a graphic encyclopaedia of the geographical information about the world, continents, countries or regions. When consulted properly, these maps provide a wealth of generalised information regarding location, relief, drainage, climate, vegetation, distribution of cities and towns, population, location of industries, transport-network system, tourism and heritage sites, etc.

Types of Maps Based on Function: The maps may also be classified on the basis of their functions. For example, a political map serves the function of providing administrative divisions of a continent or a country and a soil map shows the distribution of different types of soils. Broadly, maps based on their functions may be classified into physical maps and cultural maps. (i) Physical Maps: Physical maps show natural features such as relief, geology, soils, drainage, elements of weather, climate and vegetation, etc. (a) Relief Maps: Relief maps show general topography of an area like mountains and valleys, plains, plateaus and drainage. Figure 1.7 shows the relief and slope map of Nagpur district. (b) Geological Maps: These maps are drawn to show geological structures, rock types, etc. Figure 1.8 shows the distribution of rocks and minerals in Nagpur district. (c) Climatic Maps : These maps depict climatic regions of an area. Besides, maps are also drawn to show the distribution of temperature,

Introduction to Maps

Figure 1.7 Relief and Slope Map of Nagpur District

9

Figure 1.8 Distribution of Rocks and Minerals in Nagpur District

Practical Work in Geography

10 10

Figure 1.9 Map showing Climatic Conditions of Nagpur District

Figure 1.10 Soils of Nagpur District

Introduction to Maps

rainfall, cloudiness, relative humidity, direction and velocity of winds and other elements of weather (Fig 1.9). (d) Soil Maps : Maps are also drawn to show the distribution of different types of soil(s) and their properties (Fig. 1.10). (ii) Cultural Maps: Cultural maps show man-made features. These include a variety of maps showing population distribution and growth, sex and age, social and religious composition, literacy, levels of educational attainment, occupational structure, location of settlements, facilities and services, transportation lines and production, distribution and flow of different commodities. (a) Political Maps : These maps show the administrative divisions of an area such as country, state or district. These maps facilitate the administrative machinery in planning and management of the concerned administrative unit. (b) Population Maps: The population maps are drawn to show the distribution, density and growth of population, age and sex composition,

11 11

Figure 1.11 Nagpur District : Distribution of Population

Practical Work in Geography

distribution of religious, linguistic and social groups, occupational

12 12

structure of the population, etc. (Fig 1.11 on previous page). Population maps serve the most significant role in the planning and development of an area. (c) Economic Maps: Economic maps depict production and distribution of different types of crops and minerals, location of industries and markets, routes for trade and flow of commodities. Figures 1.12 and 1.13 show the land use and cropping patterns and the location of industries in Nagpur district respectively.

Figure 1.12 Land use and Cropping Patterns in Nagpur District

(d) Transportation Maps: These maps show roads, railway lines and the location of railway stations and airports.

Introduction to Maps

Figure 1.13 Location of Industries in Nagpur District

USES

OF

MAPS

Geographers, planners and other resource scientists use maps. In doing so, they make various types of measurements to determine distances, directions and area.

Measurement of Distance: The linear features shown on the maps fall into two broad categories, i.e. straight lines and erratic or zigzag lines. The measurement of straight line features like roads, railway lines and canals is simple. It can be taken directly with a pair of dividers or a scale placed on the map surface. However, distances are required, more often, along erratic paths, i.e. the coastlines, rivers and streams. The distances along all such features can be measured by placing a thread at the starting point and carrying it along the line up to the end point. The thread is then stretched and measured to determine the distance. It can also be measured by using a simple instrument called Rotameter.

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The wheel of the 'rotameter' is moved along the route to measure the distance.

14 14

Measurement of Direction: Direction is defined as an imaginary straight line on the map showing the angular position to a common base direction. The line pointing to the north is zero direction or the base direction line. A map always shows the north direction. All other directions are determined in to this relation. The north direction enables the mapuser to locate different features with respect to each other. The four commonly known directions are Figure 1.14 Cardinal and Intermediate Directions

North, South, East and West. These are also called the cardinal points. In between the cardinal points, one may have several intermediate directions (Fig. 1.14).

Measurement of Area: The measurement of area of features like that of administrative and geographic units is also carried out over the surface of the map by map-users. There are different methods in which areas can be determined. One of the simplest but not very accurate method to determine the area is by means of regular pattern of squares. In this method, the area to be measured is covered by squares by placing a sheet of graph paper beneath the map on an illuminated tracing table or by tracing the area onto the square sheet. The total number of 'whole squares' are summed up, together with 'partial squares'. The area is then determined by a simple equation : Area

=

(

)

Sum of whole squares + Sum of partial squares x Map Scale 2

The area can also be calculated by using a fixed area polar planimeter (Box 1.1).

Introduction to Maps

Box 1.1 Measurement of Area using Polar Planimeter The area calculation is also carried out using Polar Planimeter. In this instrument, a measure is made of the movement of a rod whose locus is constrained by having one end fixed to a radial arc. The area to be measured is traced along its perimeter in a clockwise direction with an index mark, starting from one convenient point to which the index of the tracing arm must exactly return. Reading on the dial, before and after the tracing of area’s perimeter, will give a value in instrumental units. These readings are multiplied by the same constant for the particular instrument to convert into areas in square inches or centimetres.

EXERCISE 1. Choose the right answer from the four alternatives given below: i) Which one of the following is essential for the network of lines and polygons to be called a map ? (a) Map Legend (b) Symbols (c) North Direction (d) Map Scale ii) A map bearing a scale of 1 : 4000 and larger is called : (a) Cadastral map (b) Topographical map (c) Wall map (d) Atlas map iii) Which one of the following is NOT an essential element of maps ? (a) Map Projection (b) Map Generalisation (c) Map Design (d) History of Maps

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2. Answer the following questions in about 30 words: (i) What is map generalisation ?

16 16

(ii) Why is map design important ? (iii) What are different types of small-scale maps ? (iv) List out two major types of large-scale maps ? (v) How is a map different from a sketch ? 3. Write an explanatory account of types of maps.

Map Scale

Chapter 2

Map Scale You have read in Chapter 1 that the scale is an essential element of all types of maps. It is so important that if a network of lines and polygons does not carry a scale, we call it a “sketch”. Why is the scale so important ? What does it mean ? What are the different methods of showing the scale on a map? How useful is the scale in measuring the distances and the area? These are some of the questions which will be taken up in the present chapter. Glossary Denominator: The number below the line in a fraction. For example, in a fraction of 1 : 50,000, 50,000 is the denominator. Numerator: The number above the line in a fraction. For example, in a fraction of 1 : 50,000, 1 is the numerator. Representative Fraction: A method of scale of a map or plan expressed as a fraction showing the ratio between a unit distance on the map or plan, and the distance measured in the same units on the ground.

What is Scale ? You must have seen maps with a scale bar indicating equal divisions, each marked with readings in kilometres or miles. These divisions are used to find out the ground distance on the map. In other words, a map scale provides the relationship between the map and the whole or a part of the earth’s surface shown on it. We can also express this relationship as a ratio of distances between two points on the map and the corresponding distance between the same two points on the ground.

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There are at least three ways in which this relationship can be

18

expressed. These are: 1. Statement of Scale 2. Representative Fraction (R. F.) 3. Graphical Scale Each of these methods of scale has advantages and limitations. But before taking up these issues, let us understand that the scale is normally expressed in one or the other system of measurement. You must have read and/or used kilometre, metre, centimetre etc. to measure the linear distances between two points on the ground. You might have also heard of miles, furlongs, yards, feet, etc. These are two different systems of measurement of the distances used in different countries of the world. Whereas the former system is referred to as the Metric System of Measurement and presently used in India and many other countries of the world, the latter system is known as the English System of Measurement and is prevalent in both the United States and the United Kingdom. India also used this system for measuring/showing linear distances before 1957. The units of measurement of these systems are given in Box 2.1.

METHODS

OF

SCALE

As mentioned above, the scale of the map may be expressed using one or a combination of more than one methods of scale. Let us see how these methods are used and what are their advantages and limitations.

Box 2.1 Systems of Measurements Metric System of Measurement 1 km

=

1000 Metres

1 Metre

=

100 Centimetres

1 Centimetre

=

10 Millimetres

English System of Measurement 1 Mile

=

8 Furlongs

1 Furlong

=

220 Yards

1 Yard

=

3 feet

1 Foot

=

12 Inches

Map Scale

1. Statement of Scale: The scale of a map may be indicated in the form of a written statement. For example, if on a map a written statement appears stating 1 cm represents 10 km, it means that on that map a distance of 1 cm is representing 10 km of the corresponding ground distance. It may also be expressed in any other system of measurement, i.e. 1 inch represents 10 miles. It is the simplest of the three methods. However, it may be noted that the people who are familiar with one system may not understand the statement of scale given in another system of measurement. Another limitation of this method is that if the map is reduced or enlarged, the scale will become redundant and a new scale is to be worked out. 2. Graphical or Bar Scale:

The second type of scale shows map

distances and the corresponding ground distances using a line bar with primary and secondary divisions marked on it. This is referred to as the graphical scale or bar scale (Fig. 2.1). It may be noted that the scale readings as shown on the bar scale in Figure 2.1 reads only in kilometres and metres. In yet another bar scale the readings may be shown in miles and furlongs. Hence, like the statement of scale method, this method also finds restricted use for only those who can understand it. However, unlike the statement of the scale method, the graphical scale stands valid even when the map is reduced or enlarged. This is the unique advantage of the graphical method of the map scale.

Figure 2.1

3. Representative Fraction ( R. F. ): The third type of scale is R. F. It shows the relationship between the map distance and the corresponding ground distance in units of length. The use of units to express the scale makes it the most versatile method. R. F. is generally shown in fraction because it shows how much the real world is reduced to fit on the map. For example, a fraction of 1 : 24,000 shows that one unit of length on the map represents 24,000 of the same units on the ground i.e. one mm, one cm or one inch

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on the map representing 24,000 mm, 24,000 cm and 24,000 inches, respectively of the ground. It may, however, be noted that while converting

20

the fraction of units into Metric or English systems, units in centimetre or inch are normally used by convention. This quality of expressing scale in units in R. F. makes it a universally acceptable and usable method. Let us take R. F. of 1 : 36,000 to elaborate the universal nature of R. F. If the given scale is 1: 36,000, a person acquainted with the Metric System will read the given units by converting them into cm, i.e. the distance of 1 unit on the map as 1 cm and the distance of 36,000 units on the ground distance as 36,000 cm. These values may subsequently be converted into a statement of scale, i.e. 1 cm represents 360 metres. (by dividing values in denominator by the number of centimetres in a metre, i.e. 100). Yet another user of the map familiar with the English system of measurement will understand the map scale by converting it into a statement of scale convenient to him/her and read the map scale as 1 inch represents 1,000 yards. The said statement of scale will be obtained by dividing 36,000 units in the denominator by 36 (number of inches in a yard).

CONVERSION

OF

SCALE

If you have carefully read the advantages and limitations of the different methods of scale, then it will not be difficult for you to convert the Statement of Scale into Representative Fraction and vice-versa.

Statement of Scale into R. F. Problem

Convert the given Statement of Scale of 1 inch represents 4 miles into R. F.

Solution

The given Statement of Scale may be converted into R. F. using the following steps. 1 inch represents 4 miles

or

1 inch represents 4 x 63,360 inches (1 mile = 63,360 inches)

or NOTE :

1 inch represents 253,440 inches We can now replace the character “inches” into “units” and read it as : 1 unit represents 253,440 Units

Answer

R. F. 1 : 253, 440

Map Scale

R. F. into Statement of Scale Problem

Convert R. F. 1 : 253, 440 into Statement of Scale (In Metric System)

Solution

The given R. F. of 1 : 253, 440 may be converted into Statement of Scale using the following steps : 1 : 253, 440 means that 1 unit on the map represents 253, 440 units on the ground.

or

1 cm represents 253, 440/100,000 (1 km = 100,000 cm)

or

1 cm represents 2.5344 km After rounding of up to 2 decimals, the answer will be :

Answer

1 cm represents 2.53 km

Construction of the Graphical/Bar Scale Problem 1

Construct a graphical scale for a map drawn at a scale of 1 : 50,000 and read the distances in kilometre and metre.

NOTE:

By convention, a length of nearly 15 cm is taken to draw a graphical scale.

Calculations To get the length of line for the graphical scale, these steps may be followed: 1 : 50,000 means that 1 unit of the map represents 50,000 units on the ground or

1 cm represents 50,000 cm

or

15 cm represents 50,000 x 15/100,000 km

or

15 cm represents 7.5 km

Since the value of 7.5 (km) is not a round number, we can choose 5 or 10 (km) as the round number. In the present case, we choose 5 as the round number. To determine the length of the line to show 5 km, the following calculations are to be carried out: 7.5 km is represented by a line of 15 cm 5 km will be represented by a line of 15 x 5/7.5 or

5 km will be represented by a line of 10 cm

Construction The graphical scale may be constructed by following these steps: Draw a straight line of 10 cm and divide it into 5 equal parts and assign a value of 1 km each for 4 right side divisions from the 0 mark. Also divide the extreme left side division into 10 equal parts and mark each

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division by a value of 100 metres, beginning from 0. (You may also divide

22

it into 2, 4, or 5 parts and assign a value of 500, 250, or 200 metres to each of the subdivisions respectively from 0.

Figure 2.2

Problem 2

Construct a graphical scale when the given Statement of Scale is 1 inch representing 1 mile and read the distances in miles and furlongs.

NOTE:

By convention, a length of nearly 6 inches is taken to

Calculations

draw a graphical scale. To get the length of line for the graphical scale, these steps may be followed: 1 inch represents 1 mile or 6 inches represents 6 miles

Construction

The graphical scale may be constructed in the following

steps: Draw a straight line of 6 inches and divide it into 6 equal parts and assign a value of 1 mile each for 5 right side divisions. Also divide the extreme left side division into 4 equal parts and mark each division by a value of 2 miles each, beginning from 0.

Figure 2.3

Problem 3

Construct a graphical scale when the given R. F. is 1 : 50,000 and read the distances in miles and furlongs.

Calculations

To get the length of the line for the graphical scale, these steps may be followed: 1 : 50,000 means that 1 unit represents 50,000 units or 1 inch represents 50,000 inches. or 6” represents 50,000 x 6/63,360 miles =

6’ represents 4.73 miles

Map Scale

Since a figure of 4.73 (miles) is not a round number, we take 5 as the round number. To determine the length of the line to show 5 km, the following calculations are to be carried out : 4.73 miles are represented by a line of 6 inches 5 miles will be represented by a line of 6 x 5/4.73 = Construction

5 miles will be represented by a line of 6.34 inches The graphical scale may be constructed in the following steps:

To construct a graphical scale to show 5 miles we need to draw a line of 6.34 inches and divide it into 5 equal parts. The question is how can an unequal line of 6.3 inches be divided into 5 equal parts. To do so we can use the following procedure: Draw a straight line of 6.3 inches. ’ Draw lines at an angle of 400 or 450 from the start and end ’

nodes of the lines and divide them into 5 equal parts of 1 or 1.5 inches each. ’ Draw dotted lines joining the divisions marked on the two lines. ’

Mark the intersections of these lines at the primary scale.

By doing so, you will divide the unequal line of 6.3 inches into 5 equal parts. You can repeat the same way to divide the extreme left part on the primary scale into 4 or 8 parts to show the number of furlongs that are equivalent to 1 mile.

23 Figure 2.4 Drawing of equal divisions in a graphical scale

Practical Work in Geography

EXERCISE 1. Choose the right answer from the four alternatives given below:

24

(i)

Which one of the following methods of scale is a universal method? (a) Simple Statement (b) Representative Fraction (c) Graphical Scale

(ii)

(d) None of the above Map distance in a scale is also known as: (a) Numerator (b) Denominator (c) Statement of Scale (d) Representative Fraction

(iii)

‘Numerator’ in scale represents: (a) Ground distance (b) Map distance (c) Both the distances (d) None of the above

2. Answer the following questions in about 30 words: (i) What are the two different systems of measurement? (ii) Give one example each of statement of scale in Metric and English system. (iii) Why is the Representative Fraction method called a Universal method? (iv) What are the major advantages of the graphical method? 3. Convert the given Statement of Scale into Representative Fraction (R. F.). (i) 5 cm represents 10 km (ii) 2 inches represents 4 miles (iii) 1 inch represents 1 yard (iv) 1 cm represents 100 metres 4. Convert the given Representative Fraction (R. F.) into Statement of Scale in the System of Measurement shown in parentheses: (i) 1 : 100,000 (into km) (ii) 1 : 31680 (into furlongs)

Map Scale

(iii) 1 : 126,720 (into miles) (iv) 1 : 50,000 (into metres) 5.

Construct a graphical scale when the given R. F. is 1 : 50,000 and read the distances in kilometre and metre.

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26

Chapter 3

Latitude, Longitude and Time THE EARTH is nearly a sphere. It is because of the fact that the equatorial radius and the polar radius of the earth is not the same. The rotation of the earth over its axis produces bulging at the equator. Hence, the actual shape resembles that of an oblate spheroid. The shape of the earth presents some difficulties in positioning its surface features, as there is no point of reference from which to measure the relative positions of other points. Hence, a network of imaginary lines is drawn on a globe or a map to locate various places. Let us find out what are these lines and how are they drawn. The spinning of the earth on its axis from west to east provides two natural points of reference, i.e. North and South Poles. They form the basis for the geographical grid. A network of intersecting lines is drawn for the purpose of fixing the locations of different features. The grid consists of two sets of horizontal and vertical lines, which are called parallels of latitudes and the meridians of longitudes. Horizontal lines are drawn parallel to each other in east-west direction. The line drawn midway between the North Pole and the South Pole is called the equator. It is the largest circle and divides the globe into two equal halves. It is also called a great circle. All the other parallels get smaller in size, in proportion to their distance from the equator towards the poles and divide the earth into two unequal halves, also referred to as the small circles. These imaginary lines running east-west are commonly known as the parallels of latitude. The vertical lines running north-south, join the two poles. They are called the meridians of longitude. They are spaced farthest apart at the equator and converge at a point at each pole.

Latitude, Longitude and Time

The latitudes and longitudes are commonly referred to as geographical coordinates as they provide systematic network of lines upon which the position of various surface features of the earth, can be represented. With the help of these coordinates, location, distance and direction of various points can be easily determined. Although an infinite number of parallels and meridians may be drawn on a globe, only a selected number of them are usually drawn on a map. Latitudes and longitudes are measured in degrees (°) because they represent angular distances. Each degree is further divided into 60 minutes ( ‘ ) and each minute into 60 seconds ( “ ).

Glossary Parallels of Latitude : The parallels of latitude refer to the angular distance, in degrees, minutes and seconds of a point north or south of the Equator. Lines of latitude are often referred to as parallels. Meridians of Longitude : The meridians of longitude refer to the angular distance, in degrees, minutes, and seconds, of a point east or west of the Prime (Greenwich) Meridian. Lines of longitude are often referred to as meridians.

PARALLELS

OF

LATITUDES

The latitude of a place on the earth’s surface is its distance north or south of the equator, measured along the meridian of that place as an angle from the centre of the earth. Lines joining places with the same latitudes are called parallels. The value of equator is 0° and the latitude of the poles are 90°N and 90°S (Fig. 3.1 on the next page). If parallels of latitude are drawn at an interval of one degree, there will be 89 parallels in the northern and the southern hemispheres each. The total number of parallels thus drawn, including the equator, will be 179. Depending upon the location of a feature or a place north or south of the equator, the letter N or S is written along with the value of the latitude. If the earth were a perfect sphere, the length of 10 of latitude (a one degree arc of a meridian) would be a constant value, i.e. 111 km everywhere on the earth. This length is almost the same as that of a

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degree of longitude at the equator. But to be precise, a degree of latitude changes slightly in length from the equator to the poles. While at the equator, it is

28

110.6 km at the poles, it is 111.7 km. Latitude of a place may be determined with the help of the altitude of the sun or the Pole Star.

DRAWING THE PARALLELS OF LATITUDES How to draw the parallels of latitudes? Draw a circle Figure 3.1 Parallels of Latitudes

and divide it into two equal halves by drawing a horizontal line in the centre. This represents the equator. Place a protractor on this circle in a way that 0° and 180° line on the protractor coincide with the equator on the paper. Now to draw 20°S, mark two points at an angle of 20° from the equator, east and west in the lower half of the circle, as shown in Fig. 3.2. The arms of the angle cut the circle at two points. Join these two points by a line parallel to the equator. It will be 200S.

MERIDIANS Figure 3.2 Drawing of Parallels of Latitudes

OF

LONGITUDE

Unlike the parallels of latitude which are circles, the meridians of longitude are semi-circles that converge at the poles. If opposite meridians are taken together, they complete a circle, but, they are valued separately as two meridians. The meridians intersect the equator at right angles. Unlike the parallels of latitude, they are all equal in length. For convenience of numbering, the meridian of longitude passing through the Greenwich observatory (near London) has been adopted as the Prime Meridian by an international agreement and has been given the value of 0°. The longitude of a place is its angular distance east or west of the Prime Meridian. It is also measured in degrees. The longitudes vary from 0° to 180°

Latitude, Longitude and Time

eastward and westward of the Prime Meridian (Fig. 3.3). The part of the earth east of the Prime Meridian is called the eastern hemisphere and in its west referred to as the western hemisphere.

Drawing the Meridians of Longitude How to draw the lines of longitude? Draw a circle whose centre represents the North Pole. The circumference will represent the equator. Draw a vertical line through the centre of the circle, i.e. crossing the North Pole. This represents the 0° and 180° meridians, which meet at the North Pole (Fig. 3.4). When you look at a map, the east is towards your right and the west is towards your left. However, to draw a longitude, imagine that you are on the North Pole, i.e. at the centre of the circle as shown in Fig. 3.4. Observe now that the relative directions of east and west would reverse in this case and east would be towards your left while west would be towards your right. Now, draw 45° E and W as shown in Fig. 3.5 For this, place your protractor along the vertical line, coinciding with the 0° and 180° meridians and then measure 45° on both the sides, which will denote 45° E meridian and 45° W meridian on your left and right, respectively. The diagram will represent the appearance of the earth if we look at it from directly above the North Pole.

LONGITUDE

AND

Figure 3.3 Meridians of Longitude

Figure 3.4 Meridians of 00 and 1800 join at the North Pole

TIME

We all know that the earth rotates from west to east over its axis. It makes the sun rise in the east and set in the west. The rotation of the earth over its axis takes 24 hours to complete one circle or 360° of longitudes. As 180° of longitudes fall both east and west of the Prime Meridian, the sun, thus takes 12 hours’ time to traverse the

29 Figure 3.5 Drawing of Meridians of Longitude

Practical Work in Geography

Table 3.1 A Comparison between the Parallels of Latitudes and t he Meridians of Longitudes

30

S. No.

Parallels of Latitude

Meridians of Longitude

1.

Latitude is the angular

Longitude is the angular

distance of a point north or south of the equator as

distance along the equator measured in

measured in degrees.

degrees. It is measured east or west of Greenwich (0°), from 0° to 180°.

2.

All latitudes are parallel to the equator.

All meridians of longitude converge at the poles.

3.

On a globe, parallels of latitudes appear as circles.

All meridians of longitude appear as circles running through

4.

The distance between two

the poles. The distance between

latitudes is approximately

two longitudes is

111 km.

maximum at the equator (111.3 km) and minimum at the poles (0 km). Midway, at 450 of latitude, it is 79 km.

5.

The 00 latitude is referred to

There are 360° of

as the equator and the 90° as the poles.

longitude, 180° each in the east and west of the Prime Meridian.

6.

The latitudes from the equator to the poles are used to demarcate temperature zones, i.e. 0° to 23 ½° north and south as the torrid zone, 23 ½° to 66 ½° as the temperate zone and 66 ½° to 90° as the frigid

The longitudes are used to determine the local time with reference to the time at Prime Meridian.

Latitude, Longitude and Time

eastern and western hemispheres. In other words, the sun traverses 150 of longitudes per hour or one degree of longitude in every four minutes of time. It may further be noted that the time decreases when we move from west to east and increases with our westward movement. The rate of the time at which the sun traverses over certain degrees of longitudes is used to determine the local time of an area with respect to the time at the Prime Meridian (0°Longitude). Let us try to understand the question of the determination of time with respect to the Prime Meridian with the following set of examples : Example 1 : Determine the local time of Thimpu (Bhutan) located at 90° east longitude when the time at Greenwich (0°) is 12.00 noon. Statement : The time increases at a rate of 4 minutes per one degree of longitude, east of the Prime Meridian. Solution : Difference between Greenwich and Thimpu = 90° of longitudes Total Time difference = 90 x 4 = 360 minutes = 360/60 hours = 6 hours\Local time of Thimpu is 6 hours Greenwich,

more

than

that

at

i.e. 6.00 p.m.

Example 2 : Determine the local time of New Orleans (the place, which was worst affected by Katrina Hurricane in October 2005), located at 900 West longitude when the time at Greenwich (00) is 12.00 noon. Statement : The time decrease, at a rate of 4 minutes per one degree of longitude, west of the prime meridian. Solution : Difference between Greenwich and New Orleans = 90° of longitudes Total Time difference

= 90 x 4 = 360 minutes = 360/60 hours

= 6 hours\Local time of New Orleans is 6 hours less than that at Greenwich, i.e. 6.00 a. m. In the same way, the time may be determined for any place in the world. However, in order to maintain uniformity of time as far as possible within the territorial limits of a country, the time at the central meridian of the country is taken as the Standard Meridian and its local time is taken as the standard time for the whole country. The Standard Meridian is selected in a manner that it is divisible by 150° or 7° 30’ so that the difference

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between its standard time and the Greenwich Mean Time may be

32

expressed as multiples of an hour or half an hour. The Indian Standard Time is calculated from 82°30’E meridian passing through Mirzapur. Therefore, IST is plus 5.30 hours from the GMT ((82°30’ x 4) (60 minutes=5 hours 30 minutes). Similarly, all countries of the world choose the standard meridian within their territory to determine the time within their administrative boundaries. The countries with large eastwest span may choose more than one standard meridian to get more than one time zone such as Russia, Canada and the United States of America. The world is divided into 24 major time zones (Fig. 3.6).

Figure 3.6 Major Time Zones of the World

INTERNATIONAL DATE LINE While the world is divided into 24 time zones, there has to be a place where there is a difference in days, somewhere the day truly “starts” on the planet. The 180° line of longitude is approximately where the International Date Line passes. The time at this longitude is exactly 12 hours from the 00 longitude, irrespective of one travels westward or eastward from the Prime Meridian. We know that time decreases east of

Latitude, Longitude and Time

the Prime Meridian and increases to its west. Hence, for a person moving east of the Prime Meridian, the time would be 12 hours less than the time at 0° longitude. For another person moving westward, the time would be 12 hours more than the Prime Meridian. For example, a person moving eastward on Tuesday will count the day as Wednesday once the International Date Line is crossed. Similarly, another person starting his journey on the same day, but moving westward will count the day as Monday after crossing the line.

EXERCISE 1. Answer the following questions in about 30 words: (i) Which are the two natural points of references on the earth? (ii) What is a great circle? (iii) What are coordinates? (iv) Why does the sun appear to be moving from east to west? (v) What is meant by local time? 2. Distinguish between latitudes and longitudes.

ACTIVITY 1. Find out the locations of the following places with the help of your atlas and write their latitudes and longitudes.

Place

Latitude

Longitude

(i) Mumbai (ii) Vladivostok (iii) Cairo (iv) New York (v) Ottawa (vi) Geneva (vii) Johannesburg (viii) Sydney

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2. What would be the time of the following cities if the time at Prime

34

Meridian is 10 a.m. (i) Delhi (ii) London (iii) Tokyo (iv) Paris (v) Cairo (vi) Moscow

Map Projections

Chapter 4

Map Projections What is map projection? Why are map projections drawn? What are the different types of projections? Which projection is most suitably used for which area? In this chapter, we will seek the answers of such essential questions.

MAP PROJECTION Map projection is the method of transferring the graticule of latitude and longitude on a plane surface. It can also be defined as the transformation of spherical network of parallels and meridians on a plane surface. As you know that, the earth on which we live in is not flat. It is geoid in shape like a sphere. A globe is the best model of the earth. Due to this property of the globe, the shape and sizes of the continents and oceans are accurately shown on it. It also shows the directions and distances very accurately. The globe is divided into various segments by the lines of latitude and longitude. The horizontal lines represent the parallels of latitude and the vertical lines represent the meridians of the longitude. The network of parallels and meridians is called graticule. This network facilitates drawing of maps. Drawing of the graticule on a flat surface is called projection. But a globe has many limitations. It is expensive. It can neither be carried everywhere easily nor can a minor detail be shown on it. Besides, on the globe the meridians are semi-circles and the parallels are circles. When they are transferred on a plane surface, they become intersecting straight lines or curved lines.

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NEED FOR MAP PROJECTION The need for a map projection mainly arises to have a detailed study of a

36

region, which is not possible to do from a globe. Similarly, it is not easy to compare two natural regions on a globe. Therefore, drawing accurate large-scale maps on a flat paper is required. Now, the problem is how to transfer these lines of latitude and longitude on a flat sheet. If we stick a flat paper over the globe, it will not coincide with it over a large surface without being distorted. If we throw light from the centre of the globe, we get a distorted picture of the globe in those parts of paper away from the line or point over which it touches the globe. The distortion increases with increase in distance from the tangential point. So, tracing all the properties like shape, size and directions, etc. from a globe is nearly impossible because the globe is not a developable surface. In map projection we try to represent a good model of any part of the earth in its true shape and dimension. But distortion in some form or the other is inevitable. To avoid this distortion, various methods have been devised and many types of projections are drawn. Due to this reason, map projection is also defined as the study of different methods which have been tried for transferring the lines of graticule from the globe to a flat sheet of paper. Glossary Map projection: It is the system of transformation of the spherical surface onto a plane surface. It is carried out by an orderly and systematic representation of the parallels of latitude and the meridians of longitude of the spherical earth or part of it on a plane surface on a conveniently chosen scale. Lexodrome or Rhumb Line: It is a straight line drawn on Mercator’s projection joining any two points having a constant bearing. It is very useful in determining the directions during navigation. The Great Circle: It represents the shortest route between two points, which is often used both in air and ocean navigation. Homolograhic Projection: A projection in which the network of latitudes and longitudes is developed in such a way that every graticule on the map is equal in area to the corresponding graticule on the globe. It is also known as the equal-area projection. Orthomorphic Projection: A projection in which the correct shape of a given area of the earth’s surface is preserved.

Map Projections

ELEMENTS

OF

MAP PROJECTION

a. Reduced Earth: A model of the earth is represented by the help of a reduced scale on a flat sheet of paper. This model is called the “reduced earth”. This model should be more or less spheroid having the length of polar diameter lesser than equatorial and on this model the network of graticule can be transferred.

b. Parallels of Latitude: These are the circles running round the globe parallel to the equator and maintaining uniform distance from the poles. Each parallel lies wholly in its plane which is at right angle to the axis of the earth. They are not of equal length. They range from a point at each pole to the circumference of the globe at the equator. They are demarcated as 0º to 90º North and South latitudes.

c. Meridians of Longitude: These are semi-circles drawn in northsouth direction from one pole to the other, and the two opposite meridians make a complete circle, i.e. circumference of the globe. Each meridian lies wholly in its plane, but all intersect at right angle along the axis of the globe. There is no obvious central meridian but for convenience, an arbitrary choice is made, namely the meridian of Greenwich, which is demarcated as 0° longitudes. It is used as reference longitudes to draw all other longitudes

d. Global Property: In preparing a map projection the following basic properties of the global surface are to be preserved by using one or the other methods: (i) Distance between any given points of a region; (ii) Shape of the region; (iii) Size or area of the region in accuracy; (iv) Direction of any one point of the region bearing to another point.

CLASSIFICATION

OF

MAP PROJECTIONS

Map Projections may be classified on the following bases:

a. Drawing Techniques: On the basis of method of construction, projections are generally classified into perspective, non-perspective and

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conventional or mathematical. Perspective projections can be drawn

38

taking the help of a source of light by projecting the image of a network of parallels and meridians of a globe on developable surface. Non–perspective projections are developed without the help of a source of light or casting shadow on surfaces, which can be flattened. Mathematical or conventional projections are those, which are derived by mathematical computation, and formulae and have little relations with the projected image.

b. Developable Surface: A developable surface is one, which can be flattened, and on which, a network of latitude and longitude can be projected. A non-developable surface is one, which cannot be flattened without shrinking, breaking or creasing. A globe or spherical surface has the property of non-developable surface whereas a cylinder, a cone and a plane have the property of developable surface. On the basis of nature of developable surface, the projections are classified as cylindrical, conical and zenithal projections. Cylindrical projections are made through the use of cylindrical developable surface. A paper-made cylinder covers the globe, and the parallels and meridians are projected on it. When the cylinder is cut open, it provides a cylindrical projection on the plane sheet. A Conical projection is drawn by wrapping a cone round the globe and the shadow of graticule network is projected on it. When the cone is cut open, a projection is obtained on a flat sheet. Zenithal projection is directly obtained on a plane surface when plane touches the globe at a point and the graticule is projected on it. Generally, the plane is so placed on the globe that it touches the globe at one of the poles. These projections are further subdivided into normal, oblique or polar as per the position Figure 4.1 Conversions from a Globe to a flat surface produces distortions in area, shape and directions.

of the plane touching the globe. If the developable surface touches the globe at the equator, it is called the

Map Projections

Figure 4.2 A conical projection from a Globe to a Flat Map

equatorial or normal projection. If it is tangential to a point between the pole and the equator, it is called the oblique projection; and if it is tangential to the pole, it is called the polar projection.

c. Global Properties: As mentioned above, the correctness of area, shape, direction and distances are the four major global properties to be preserved in a map. But none of the projections can maintain all these properties simultaneously. Therefore, according to specific need, a projection can be drawn so that the desired quality may be retained. Thus, on the basis of global properties, projections are classified into equal area, orthomorphic, azimuthal and equi-distant projections. Equal Area Projection is also called homolographic projection. It is that projection in which areas of various parts of the earth are represented correctly. Orthomorphic or True-Shape projection is one in which shapes of various areas are portrayed correctly. The shape is generally maintained at the cost of the correctness of area. Azimuthal or True-Bearing projection is one on which the direction of all points from the centre is correctly represented. Equi-distant or True Scale projection is that where the distance or scale is correctly maintained. However, there is no such projection, which maintains the scale correctly throughout. It can be

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maintained correctly only along some selected parallels and meridians as per the requirement.

40

d. Source of Light: On the basis of location of source of light, projections may be classified as gnomonic, stereographic and orthographic. Gnomonic projection is obtained by putting the light at the centre of the globe. Stereographic projection is drawn when the source of light is placed at the periphery of the globe at a point diametrically opposite to the point at which the plane surface touches the globe. Orthographic projection is drawn when the source of light is placed at infinity from the globe, opposite to the point at which the plane surface touches the globe.

CONSTRUCTING SOME SELECTED PROJECTIONS a. Conical Projection with one Standard Parallel A conical projection is one, which is drawn by projecting the image of the graticule of a globe on a developable cone, which touches the globe along a parallel of latitude called the standard parallel. As the cone touches the globe located along AB, the position of this parallel on the globe coinciding with that on the cone is taken as the standard parallel. The length of other parallels on either side of this parallel are distorted. (Fig. 4.3) Example Construct a conical projection with one standard parallel for an area bounded by 10º N to 70º N latitude and 10º E to 130º E longitudes when the scale is 1:250,000,000 and latitudinal and longitudinal interval is 10º. Calculation Radius of reduced earth R =

640,000,000 = 2.56 cm 250,000,000

Standard parallel is 40º N (10, 20, 30, 40, 50, 60, 70) Central meridian is 70º E (10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130) Construction (i)

Draw a circle or a quadrant of 2.56 cm radius marked with angles

(ii)

COE as 10º interval and BOE and AOD as 40º standard parallel. A tangent is extended from B to P and similarly from A to P, so that AP and BP are the two sides of the cone touching the globe and forming Standard Parallel at 40° N.

Map Projections

(iii)

The arc distance CE represents the interval between parallels.

(iv)

A semi-circle is drawn by taking this arc distance. X-Y is the perpendicular drawn from OP to OB.

(v)

A separate line N-S is taken on which BP distance is drawn representing standard parallel. The line NS becomes the central meridian.

(vi)

Other parallels are drawn by taking arc distance CE on the

(vii)

central meridian. The distance XY is marked on the standard parallel at 40° for drawing other meridians.

(viii) Straight lines are drawn by joining them with the pole. Properties 1. All the parallels are arcs of concentric circle and are equally spaced. 2. All meridians are straight lines merging at the pole. The meridians intersect the parallels at right angles. 3. The scale along all meridians is true, i.e. distances along the meridians are accurate. 4. An arc of a circle represents the pole. 5. The scale is true along the standard parallel but exaggerated away from the standard parallel. 6. Meridians become closer to each other towards the pole. 7. This projection is neither equal area nor orthomorphic.

41

Figure 4.3 Simple Conical Projection with one standard parallel

Practical Work in Geography

Limitations

42

1. It is not suitable for a world map due to extreme distortions in the hemisphere opposite the one in which the standard parallel is selected. 2. Even within the hemisphere, it is not suitable for representing larger areas as the distortion along the pole and near the equator is larger. Uses 1. This projection is commonly used for showing areas of mid-latitudes with limited latitudinal and larger longitudinal extent. 2. A long narrow strip of land running parallel to the standard parallel and having east-west stretch is correctly shown on this projection. 3. Direction along standard parallel is used to show railways, roads, narrow river valleys and international boundaries. 4. This projection is suitable for showing the Canadian Pacific Railways, Trans-Siberian Railways, international boundaries between USA and Canada and the Narmada Valley.

b. Cylindrical Equal Area Projection The cylindrical equal area projection, also known as the Lambert’s projection, has been derived by projecting the surface of the globe with parallel rays on a cylinder touching it at the equator. Both the parallels and meridians are projected as straight lines intersecting one another at right angles. The pole is shown with a parallel equal to the equator; hence, the shape of the area gets highly distorted at the higher latitude. Example Construct a cylindrical equal area projection for the world when the R.F. of the map is 1:300,000,000 taking latitudinal and longitudinal interval as 15º. Calculation Radius of the reduced earth R =

Length of the equator 2ðR or

Interval along the equator =

640,000,000 = 2.1 cm 300,000,000

2 x 22 x 2.1 = 13.2cm 7

13.2 x15º = 0.55cm 360º

Map Projections

Construction (i) Draw a circle of 2.1 cm radius; (ii) Mark the angles of 15º, 30º, 45º, 60º, 75º and 90º for both, northern and southern hemispheres; (iii) Draw a line of 13.2 cm and divide it into 24 equal parts at a distance of 0.55cm apart. This line represents the equator; (iv) Draw a line perpendicular to the equator at the point where 0° is meeting the circumference of the circle; (v) Extend all the parallels equal to the length of the equator from the perpendicular line; and (vi) Complete the projection as shown in fig 4.4 below:

Figure 4.4 Cylindrical Equal Area Projection

Properties 1. All parallels and meridians are straight lines intersecting each other at right angle. 2. Polar parallel is also equal to the equator. 3. Scale is true only along the equator. Limitations 1. Distortion increases as we move towards the pole. 2. The projection is non-orthomorphic. 3. Equality of area is maintained at the cost of distortion in shape. Uses 1. The projection is most suitable for the area lying between 45º N and S latitudes. 2. It is suitable to show the distribution of tropical crops like rice, tea, coffee, rubber and sugarcane.

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c. Mercator’s Projection A Dutch cartographer Mercator Gerardus Karmer developed this

44

projection in 1569. The projection is based on mathematical formulae. So, it is an orthomorphic projection in which the correct shape is maintained. The distance between parallels increases towards the pole. Like cylindrical projection, the parallels and meridians intersect each other at right angle. It has the characteristics of showing correct directions. A straight line joining any two points on this projection gives a constant bearing, which is called a Laxodrome or Rhumb line. Example Draw a Mercator’s projection for the world map on the scale of 1:250,000,000 at 15º interval. Calculation Radius of the reduced earth is R =

Length of the equator 2ðR or

Interval along the equator =

250,000,000 = 1" inch 250,000,000

1x22x2 = 6.28"inches 7

6.28 x15º = 0.26" inches 360º

Construction (i) (ii)

Draw a line of 6.28" inches representing the equator as EQ: Divide it into 24 equal parts. Determine the length of each division using the following formula:

Length of Equator X interval 360 (iii)

Calculate the distance for latitude with the help of the table given below:Latitude Distance

(iv)

15º

0.265 x 1 = 0.265" inch

30º 45º

0.549 x 1 = 0.549" inch 0.881 x 1 = 0.881" inch

60º

1.317 x 1 = 1.317" inches

75º 2.027 x 1 = 2.027" inches Complete the projection as shown in Fig. 4.5

Map Projections

Figure 4.5 Mercator’s Projection

Properties 1. All parallels and meridians are straight lines and they intersect each other at right angles. 2. All parallels have the same length which is equal to the length of equator. 3. All meridians have the same length and equal spacing. But they are longer than the corresponding meridian on the globe. 4. Spacing between parallels increases towards the pole. 5. Scale along the equator is correct as it is equal to the length of the equator on the globe; but other parallels are longer than the corresponding parallel on the globe; hence the scale is not correct along them. For example, the 30º parallel is 1.154 times longer than the corresponding parallel on the globe. 6. Shape of the area is maintained, but at the higher latitudes distortion takes place. 7. The shape of small countries near the equator is truly preserved while it increases towards poles. 8. It is an azimuthal projection. 9. This is an orthomorphic projection as scale along the meridian is equal to the scale along the parallel. Limitations 1. There is greater exaggeration of scale along the parallels and meridians in high latitudes. As a result, size of the countries near

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Practical Work in Geography

the pole is highly exaggerated. For example, the size of Greenland

46

equals to the size of USA, whereas it is 1/10th of USA. 2. Poles in this projection cannot be shown as 90º parallel and meridian touching them are infinite. Uses 1. More suitable for a world map and widely used in preparing atlas maps. 2. Very useful for navigation purposes showing sea routes and air routes. 3. Drainage pattern, ocean currents, temperature, winds and their directions, distribution of worldwide rainfall and other weather elements are appropriately shown on this map

Figure 4.6 Straight lines are Laxodromes or Rhumb lines and Dotted lines are great circles

Map Projections

EXERCISE 1. Choose the right answer from the four alternatives given below: (i) A map projection least suitable for the world map: (a) Mercator (b) Simple Cylindrical (c) Conical (d) All the above (ii) A map projection that is neither the equal area nor the correct shape and even the directions are also incorrect (a) Simple Conical (b) Polar zenithal (c) Mercator (d) Cylindrical (iii) A map projection having correct direction and correct shape but area greatly exaggerated polewards is (a) Cylindrical Equal Area (b) Mercator (c) Conical (d) All the above (iv) When the source of light is placed at the centre of the globe, the resultant projection is called (a) Orthographic (b) Stereographic (c) Gnomonic (d) All the above 2. Answer the following questions in about 30 words: (i) Describe the elements of map projection. (ii) What do you mean by global property? (iii) Not a single map projection represents the globe truly. Why? (iv) How is the area kept equal in cylindrical equal area projection? 3. Differentiate between— (i) Developable and non-developable surfaces (ii) Homolographic and orthographic projections (iii) Normal and oblique projections (iv) Parallels of latitude and meridians of longitude

47

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4. Answer the following questions in not more than 125 words:

48

(i)

Discuss the criteria used for classifying map projection and state the major characteristics of each type of projection.

(ii)

Which map projection is very useful for navigational purposes?

(iii)

Explain the properties and limitations of this projection. Discuss the main properties of conical projection with one standard parallel and describe its major limitations.

ACTIVITY Construct graticule for an area stretching between 30º N to 70º N and 40º E to 30º W on a simple conical projection with one standard parallel with a scale of 1:200,000,000 and interval at an 10º apart. Prepare graticule for a Cylindrical Equal Area Projection for the world when R.F. is1: 150,000,000 and the interval is 15º apart. Draw a Mercator Projection for the world map when the R.F. is 1:400,000,000 and the interval between the latitude and longitude is 20º.

Topographical Maps

Chapter 5 Topographical Maps You know that the map is an important geographic tool. You also know that maps are classified on the basis of scale and functions. The topographical maps, which have been referred to in Chapter 1 are of utmost importance to geographers. They serve the purpose of base maps and are used to draw all the other maps. Topographical maps, also known as general purpose maps, are drawn at relatively large scales. These maps show important natural and cultural features such as relief, vegetation, water bodies, cultivated land, settlements, and transportation networks, etc. These maps are prepared and published by the National Mapping Organisation of each country. For example, the Survey of India prepares the topographical maps in India for the entire country. The topographical maps are drawn in the form of series of maps at different scales. Hence, in the given series, all maps employ the same reference point, scale, projection, conventional signs, symbols and colours. The topographical maps in India are prepared in two series, i.e. India and Adjacent Countries Series and The International Map Series of the World.

India and Adjacent Countries Series: Topographical maps under India and Adjacent Countries Series were prepared by the Survey of India till the coming into existence of Delhi Survey Conference in 1937. Henceforth, the preparation of maps for the adjoining countries was abandoned and the Survey of India confined itself to prepare and publish the topographical maps for India as per the specifications laid down for the International Map Series of the World. However, the Survey of India for the topographical maps

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Glossary Contours: Imaginary lines joining all the points of equal elevation or

50

altitude above mean sea level. They are also called “level lines”. Contour Interval: Interval between two successive contours. It is also known as vertical interval, usually written as V. I. Generally, it is constant for a given map. Cross-section: A side view of the ground cut vertically along a straight line. It is also known as a section or profile. Hachures: Small straight lines drawn on the map along the direction of maximum slope, running across the contours. They given an idea about the differences in the slope of the ground. Topographic Map: A map of a small area drawn on a large scale depicting detailed surface features both natural and man made. Relief in this map is shown by contours.

under the new series retained the numbering system and the layout plan of the abandoned India and Adjacent Countries Series. The topographical maps of India are prepared on 1 : 10,00,000, 1 : 250,000, 1 : 1,25,000, 1 : 50,000 and 1: 25,000 scale providing a latitudinal and longitudinal coverage of 4° x 4°, 1° x 1°, 30' x 30', 15' x 15' and 5' x 7' 30", respectively. The numbering system of each one of these topographical maps is shown in Fig. 5.1 (on page 51).

International Map Series of the World: Topographical Maps under International Map Series of the World are designed to produce standardised maps for the entire World on a scale of 1: 10,00,000 and 1:250,000.

Reading of Topographical Maps: The study of topographical maps is simple. It requires the reader to get acquainted with the legend, conventional sign and the colours shown on the sheets. The conventional sign and symbols depicted on the topographical sheets are shown in Fig. 5.2 (on page 52).

METHODS OF RELIEF REPRESENTATION The earth’s surface is not uniform and it varies from mountains to hills to plateaus and plains. The elevation and depressions of the earth’s surface are known as physical features or relief features of the earth. The map showing these features is called a relief map.

Topographical Maps

51

Figure 5.1 Reference Map of Topographical Sheets Published by Survey of India

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52

Figure 5.2 Conventional Signs and Symbols

A number of methods have been used to show the relief features of the Earth’s surface on maps, over the years. These methods include hachure, hill shading, layer tints, benchmarks and spot heights and contours. However, contours and spot heights are predominantly used to depict the relief of an area on all topographical maps.

Topographical Maps

CONTOURS Contours are imaginary lines joining places having the same elevation above mean sea level. A map showing the landform of an area by contours is called a contour map. The method of showing relief features through contour is very useful and versatile. The contour lines on a map provide a useful insight into the topography of an area. Earlier, ground surveys and levelling methods were used to draw contours on topographical maps. However, the invention of photography and subsequent use of aerial photography have replaced the conventional methods of surveying, levelling and mapping. Henceforth, these photographs are used in topographical mapping. Contours are drawn at different vertical intervals (VI), like 20, 50, 100 metres above the mean sea level. It is known as contour interval. It is usually constant on a given map. It is generally expressed in metres. While the vertical interval between the two successive contour lines remains constant, the horizontal distance varies from place to place depending upon the nature of slope. The horizontal distance, also known as the horizontal equivalent (HE), is large when the slope is gentler and decreases with increasing slope gradient.

Some basic features of contour lines are ’

A contour line is drawn to show places of equal heights.

’

Contour lines and their shapes represent the height and slope or gradient of the landform.

’

Closely spaced contours represent steep slopes while widely spaced contours represent gentle slope.

’

When two or more contour lines merge with each other, they represent features of vertical slopes such as cliffs or waterfalls.

’

Two contours of different elevation usually do not cross each other.

Drawing of Contours and Their Cross Sections We know that all the topographical features show varying degrees of slopes. For example, a flat plain exhibits gentler slopes and the cliffs and gorges are associated with the steep slopes. Similarly, valleys and mountain ranges are also characterised by the varying degree of slopes, i.e. steep to gentle. Hence, the spacing of contours is significant since it indicates the slope.

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Types of slope The slopes can broadly be classified into gentle, steep, concave, convex

54

and irregular or undulating. The contours of different types of slopes show a distinct spacing pattern.

Gentle Slope

Steep Slope

When the degree or angle of

When the degree or angle of

slope of a feature is very low, the

slope of a feature is high and

slope will be gentle. The

the contours are closely spaced,

contours representing this type

they inddicate steep slope.

of slope are far apart.

Gentle Slope

Steep Slope

Topographical Maps

Concave Slope

Convex Slope

A slope with a gentle gradient in

Unlike concave slope, the

the lower parts of a relief feature

convex slope is fairly gentle in

and steep in its upper parts is

the upper part and steep in the

called

slope.

lower part. As a result, the

Contours in this type of slope are

contours are widely spaced in

widely spaced in the lower parts

the upper parts and are closely

and are closely spaced in the

spaced in the lower parts.

the

concave

upper parts.

55 Concave Slope

Convex Slope

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Types of Landform

Plateau

56

A widely stretched flat–topped high Conical Hill

land, with relatively steeper slopes,

It rises almost uniformly from

rising above the adjoining plain or

the surrounding land. A conical

sea is called a plateau. The contour

hill with uniform slope and

lines representing a plateau are

narrow top is represented by

normally close spaced at the margins

concentric contours spaced

with the innermost contour showing

almost at regular intervals.

wide gap between its two sides.

Conical Slope

Plateau

Topographical Maps

VALLEY A geomorphic feature lying between two hills or ridges and formed as a result of the lateral erosion by a river or a glacier is called a valley.

‘V’-shaped Valley

‘U’ – shaped Valley

It resembles the letter V. A V-shaped

A U–shaped valley is formed by strong

valley occurs in mountainous areas.

lateral erosion of glaciers at high

The lowermost part of the V–shaped

altitudes. The flat wide bottom and

valley is shown by the innermost

steep sides makes it resemble the

contour line with very small gap

letter ‘U’.

between its two sides and the lowest

U–shaped valley is shown by the

value of the contour is assigned to it.

innermost contour line with a wide

The contour value increases with

gap between its two sides. The contour

uniform intervals for all other contour

value increases with uniform intervals

lines outward.

for all other contour lines outward.

The lowermost part of the

57

V-Shaped Valley

U-Shaped Valley

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58

Gorge

Spur

In high altitudes, gorges form in the

A tongue of land, projecting from

areas where the vertical erosion by

higher ground into the lower is called

river is more prominent than the

a spur. It is also represented by V-

lateral erosion. They are deep and

shaped contours but in the reverse

narrow river valleys with very steep

manner. The arms of the V point to

sides. A gorge is represented by very

the higher ground and the apex of ‘V’

closely-spaced contour lines on a map

to the lower ones.

with the innermost contour showing small gap between its two sides.

Gorge

Spur

Topographical Maps Waterfall and Rapids A

sudden

and

more

or

less

perpendicular descent of water from a considerable height in the bed of a river is called a waterfall. Sometimes, a waterfall succeeds or precedes with a cascading stream forming rapids

CLIFF It

is

a

very

steep

or

almost

perpendicular face of landform. On a map, a cliff may be identified by the way the contours run very close to one another, ultimately merging into one.

upstream

or

downstream

of

a

waterfall. The contours representing a waterfall merge into one another while crossing a river stream and the rapids are shown by relatively distant contour lines on a map.

59

Cliff

Waterfall

Practical Work in Geography

Steps for Drawing a Cross-section

60

The following steps may be followed to draw cross-sections of various relief features from their contours : 1. Draw a straight line cutting across the contours on the map and mark it as AB. 2. Take a strip of white paper or graph and place its edge along the AB line. 3. Mark the position and value of every contour that cuts the line AB. 4. Choose a suitable vertical scale, eg ½ cm =100 metres, to draw horizontal lines parallel to each other and equal to the length of AB. The number of such lines should be equal or more than the total contour lines. 5. Mark the appropriate values corresponding to the contour values along the vertical of the cross-section. The numbering may be started with the lowest value represented by the contours. 6. Now place the edge of the marked paper along the horizontal line at the bottom line of the cross-section in such a way that AB of the paper corresponds to the AB of the map and mark the contour points. 7. Draw perpendiculars from AB line, intersecting contour lines, to the corresponding line at the cross-section base. 8. Smoothly join all the points marked on different lines at the crosssection base.

IDENTIFICATION OF CULTURAL FEATURES FROM TOPOGRAPHICAL SHEETS Settlements, buildings, roads and railways are important cultural features shown on topographical sheets through conventional signs, symbols and colours. The location and pattern of distribution of different features help in understanding the area shown on the map.

Distribution Of Settlements It can be seen in the map through its site, location pattern, alignment and density. The nature and causes of various settlement patterns may be clearly understood by comparing the settlement map with the contour map.

Topographical Maps

Four types of rural settlements may be identified on the map (a) Compact (b) Scattered (c) Linear (d) Circular Similarly, urban centres may also be distinguished as (a) Cross-road town (b) Nodal point (c) Market centre (d) Hill station (e) Coastal resort centre (f) Port (g) Manufacturing centre with suburban villages or satellite towns (h) Capital town (i) Religious centre Various factors determine the site of settlements like (a) Source of water (b) Provision of food (c) Nature of relief (d) Nature and character of occupation (e) Defence Site of settlements should be closely examined with reference to the contour and drainage map. Density of settlement is directly related to food supply. Sometimes, village settlements form alignments, i.e. they are spread along a river valley, road, embankment, coastline – these are called linear settlements. In the case of an urban settlement, a cross-road town assumes a fan-shaped pattern, the houses being arranged along the roadside and the crossing being at the heart of the town and the main market place. In a nodal town, the roads radiate in all directions.

Transport And Communication Pattern Relief, population, size and resource development pattern of an area directly influence the means of transport and communication and their density. These are depicted through conventional signs and symbols. Means of transport and communication provide useful information about the area shown on the map.

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INTERPRETATION OF TOPOGRAPHICAL MAPS Knowledge of map language and sense of direction are essential in reading

62

and interpreting topo-sheets .You must first look for the northline and the scale of the map and orient yourself accordingly. You must have a thorough knowledge of the legends / key given in the map depicting various features. All topo-sheets contain a table showing conventional signs and symbols used in the map (Figure 5.2). Conventional signs and symbols are internationally accepted; so, anyone can read any map anywhere in the world without knowing the language of that particular country. A topographic sheet is usually interpreted under the following heads: (a) Marginal Information (b) Relief and Drainage (c) Land Use (d) Means of Transport and Communication (e) Human Settlement

Marginal Information: It includes the topographical sheet number, its location, grid references, its extent in degrees and minutes, scale, the districts covered, etc.

Relief of the Area: The general topography of the area is studied to identify the plains, plateaus, hills or mountains along with peaks, ridges, spur and the general direction of the slope. These features are studied under the following heads : ’

Hill : With concave, convex, steep or gentle slope and shape.

’

Plateau : Whether it is broad , narrow, flat, undulating or dissected.

’

Plain : Its types, i.e. alluvial, glacial, karst, coastal, marshy, etc.

’

Mountain : General elevation, peak, passes, etc.

Drainage of the Area: The important rivers and their tributaries and the type and extent of valleys formed by them, the types of drainage pattern, i.e. dendritic, radial, ring, trellis, internal, etc.

Land Use: It includes the use of land under different categories like : ’

Natural vegetation and forest (which part of the area is forested, whether it is dense forest or thin, and the categories of forest found there like Reserved, Protected, Classified / Unclassified).

Topographical Maps

’

Agricultural, orchard, wasteland, industrial, etc.

’

Facilities and Services such as schools, colleges, hospitals, parks, airports, electric substations, etc.

Transport and Communication: The means of transportation include national or state highways, district roads, cart tracks, camel tracks, footpaths, railways, waterways, major communication lines, post offices, etc.

Settlement: Settlements are studied under the following heads : ’

Rural Settlements: The types and patterns of rural settlements, i.e. compact, semi-compact, dispersed, linear, etc.

’

Urban Settlements: Type of urban settlements and their functions, i.e. capital cities, administrative towns, religious towns, port towns, hill stations, etc.

Occupation: The general occupation of the people of the area may be identified with the help of land use and the type of settlement. For example, in rural areas the main occupation of majority of the people is agriculture; in tribal regions, lumbering and primitive agriculture dominates and in coastal areas, fishing is practised. Similarly, in cities and towns, services and business appear to be the major occupations of the people.

MAP INTERPRETATION PROCEDURE Map interpretation involves the study of factors that explain the causal relationship among several features shown on the map. For example, the distribution of natural vegetation and cultivated land can be better understood against the background of landform and drainage. Likewise, the distribution of settlements can be examined in association with the levels of transport network system and the nature of topography. The following steps will help in map interpretation: ’

Find out from the index number of the topographical sheet, the location of the area in India. This would give an idea of the general characteristics of the major and minor physiographic divisions of the area. Note the scale of the map and the contour interval, which will give the extent and general landform of the area.

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’

Trace out the following features on tracing sheets. (a) Major landforms – as shown by contours and other graphical features.

64

(b) Drainage and water features – the main river and its important tributaries. (c) Land use – i.e. forest, agricultural land, wastes, sanctuary, park, school, etc. (d) Settlement and Transport pattern. ’

Describe the distributional pattern of each of the features separately

’

drawing attention to the most important aspect. Superimpose pairs of these maps and note down the relationship, if any, between the two patterns. For example, if a contour map is superimposed over a land use map, it provides the relationship between the degree of slope and the type of the land used.

Aerial photographs and satellite imageries of the same area and of the same scale can also be compared with the topographical map to update the information.

EXERCISE 1. Answer the following questions in about 30 words: (i) What are topographical maps? (ii) Name the organisation which prepares the topographical maps of India. (iii) Which are the commonly used scales for mapping our country used by the Survey of India? (iv) What are contours? (v) What does the spacing of contours indicate? (vi) What are conventional signs? 2. Write short notes on— (i) Contours (ii) ‘Marginal Information’ in Topographical sheets (iii) The Survey of India 3. Explain what is meant by ‘map interpretation’ and what procedure is followed for its interpretation.

Topographical Maps

4. If you are interpreting the cultural features from a topographical sheet, what information would you like to seek and how would you derive this information? Discuss with the help of suitable examples. 5. Draw the conventional signs and symbols for the following features— (i) International Boundary (ii) Bench Mark (iii) Villages (iv) Metalled Road (v) Footpath with bridges (vi) Places of Worship (vii)Railwayline

Exercise A Study the contour pattern and answer the following questions. 1. Name the geographical feature formed by contours. 2. Find out the contour interval in the map. 3. Find out the map distance between E and F and convert it into ground distance. 4. Name the type of slope between A and B; C and D and E and F. 5. Find out the direction of E, D and F from G.

Exercise B Study the extract from the topographical sheet No. 63K/12, as shown in the figure below and answer the following questions—

65

Practical Work in Geography

1. Convert 1:50,000 into a statement of scale. 2. Name the major settlements of the area. 3. What is the direction of flow of the river Ganga?

66

Uttar Pradesh Mirzapur and Varanasi District

Part of 63K/12

82o 40’

82o

45’

o

25o

25

15’

15’

25o

25o

10’

10’ 82o 40’

82o 45’ R. F. 1: 50,000 Part of the Topographical Sheet No 63K/12

Topographical Maps

4. At which one of the banks of river Ganga, Bhatauli is located ? 5. What is the pattern of rural settlements along the right bank of river Ganga? 6. Name the villages/settlements where Post Office/Post and Telegraph Office are located ? 7. What does the yellow colour in the area refer to? 8. What means of transportation is used to cross the river by the people of Bhatauli village ?

Exercise C Study the extract for topographical sheet 63K/12 shown in the figure on page 68 and answer the following questions. 1. Give the height of the highest point on the map. 2. River Jamtihwa Nadi is flowing through which quarter of the map ? 3. Which is the major settlement located in the east of the Kuardari Nala ? 4. What type of settlement does the area have ? 5. Name the geographical feature represented by white patches in the middle of Sipu Nadi. 6. Name the two types of vegetation shown on part of the topographical sheet. 7. What is the direction of the flow of the Kuardari ? 8. In which part of the sheet area is Lower Khajuri Dam located?

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Uttar Pradesh Mirzapur and Varanasi District

68

Part of 63K/12

82o 35’

82o

40’ 25o

25o 5’

5’

25o

25o 0’

0’ o

82

o

35’

82 R. F. 1: 50,000 Part of the Topographical Sheet No 63K/12

40’

Introduction To Aerial Photographs

Chapter 6

Introduction To Aerial Photographs We are familiar with photographs taken with normal cameras. These photographs provide us with a view of the object similar to the way we see them with our own eyes. In other words, we get a horizontal perspective of the objects photographed. For example, a photograph of a part of settlement will provide us a perspective the way it appears to us when we look at it (Fig. 6.1). Suppose we want to take a Figure 6.1 Terrestrial ‘bird’s photograph of eye view’ Mussorrie town of similar features, then we have to place ourselves somewhere in the air. When we do so and look down, we get a very different perspective. This perspective, which we get in aerial photographs, is termed as aerial perspective (Fig. 6.2). The photographs taken from an aircraft or helicopter using a precision Figure 6.2 Bird’s Eye View of Tehri camera are termed aerial photographs. Town, ttaranchal

69

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The photographs so obtained have been found to be indispensable tools

70

in the topographical mapping and interpretation of the images of the objects. Glossary Aerial Camera : A precision camera specifically designed for use in aircrafts. Aerial Film : A roll film with high sensitivity, high intrinsic resolution power and dimensionally stable emulsion support. Aerial Photography : Art, science and technology of taking aerial photographs from an air-borne platform. Aerial Photograph : A photograph taken from an air-borne platform using a precision camera. Fiducial Marks : Index marks, rigidly connected at the central or corner edges of the camera body. When the film is exposed, these marks appear on the film negative . Forward Overlap : The common area on two successive photographs in the flight direction. It is usually expressed in per cent. Image Interpretation : An act of identifying the images of the objects and judging their relative significance. Nadir Point : The foot of the perpendicular drawn from the camera lens centre on the ground plane. Principal Point : The foot of the perpendicular drawn from the camera lens centre on the photo plane. Principal Distance : The perpendicular distance from the perspective centre to the plane of the photograph. Perspective Centre : The point of origin (perspective centre) of the bundle of light rays. Photograpmmetry : The science and technology of taking reliable measurements from aerial photographs.

USES

OF

AERIAL PHOTOGRAPHS

Aerial photographs are used in topographical mapping and interpretation. These two different uses have led to the development of photogrammetry and photo/image interpretation as two independent but related sciences. Photogrammetry: It refers to the science and technology of making reliable measurements from aerial photographs. The principles used in photogrammetry facilitate precise measurements related to the length,

Introduction To Aerial Photographs

breadth and height from such photographs. Hence, they are used as the data source for creating and updating topographic maps. The development of aerial photography in India is briefly given in Box 6.I. Box 6.1 Aerial Photography in India Aerial photography in India goes back to 1920 when large-scale aerial photographs of Agra city were obtained. Subsequently, Air Survey Party of the Survey of India took up aerial survey of Irrawaddy Delta forests, which was completed during 1923–24. Subsequently, several similar surveys were carried out and advanced methods of mapping from aerial photographs were used. Today, aerial photography in India is carried out for the entire country under the overall supervision of the Directorate of Air Survey (Survey of India) New Delhi. Three flying agencies, i.e. Indian Air Force, Air Survey Company, Kolkata and National Remote Sensing Agency, Hyderabad have been officially authorised to take aerial photographs in India. The procedure for indenting aerial photographs for educational purposes could be made with APFPS Party No. 73, Directorate of Air Survey, Survey of India, West Block IV, R. K. Puram, New Delhi.

Image Interpretation: It is an art of identifying images of objects and judging their relative significance. The principles of image interpretation are applied to obtain qualitative information from the aerial photographs such as land use/land cover, topographical forms, soil types, etc. A trained interpreter can thus utilise aerial photographs to analyse the land-use changes.

ADVANTAGES OF AERIAL PHOTOGRAPHY The basic advantages that aerial photographs offer over ground based observation are :

a. Improved vantage point: Aerial photography provides a bird’s eye view of large areas, enabling us to see features of the earth surface in their spatial context.

b. Time freezing ability: An aerial photograph is a record of the surface features at an instance of exposure. It can, therefore, be used as a historical record.

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c. Broadened Sensitivity: The sensitivity of the film used in taking

72

aerial photographs is relatively more than the sensitivity of the human eyes. Our eyes perceive only in the visible region of the electromagnetic spectrum, i.e. 0.4 to 0.7 µm whereas the sensitivity of the film ranges from 0.3 to 0.9 µm.

d. Three Dimensional Perspective: Aerial photographs are normally taken with uniform exposure interval that enables us in obtaining stereo pair of photographs. Such a pair of photographs helps us in getting a three-dimensional view of the surface photographed.

TYPES

OF

AERIAL PHOTOGRAPHS

The aerial photographs are classified on the basis of the position of the camera axis, scale, angular extent of coverage and the film used. The types of the aerial photographs based on the position of optical axis and the scale are given below :

a. Types of Aerial Photographs Based on the Position of the Cameral Axis: On the basis of the position of the camera axis, aerial photographs are classified into the following types : (i) Vertical photographs (ii) Low oblique photographs (iii) High oblique photographs (i) Vertical Photographs: While taking aerial photographs, two distinct axes are formed from the camera lens centre, one towards the ground plane and the other towards the photo plane. The perpendicular dropped from the camera lens centre to the ground plane is termed as the vertical axis, whereas the plumb line drawn from the lens centre to the photo plane is known as the photographic/optical axis. When the photo plane is kept parallel to the ground plane, the two axes also coincide with each other. The photograph so obtained is known as vertical aerial photograph (Figures 6.3 and 6.4). However, it is normally very difficult to achieve perfect parallelism between the two planes due to the fact that the aircraft flies over the curved surface of the earth. The photographic axis, therefore, deviates from the vertical axis. If such a deviation is within the range of plus or minus 3o, the near-vertical aerial photographs are obtained. Any photography with an unintentional deviation of more than 3o in the optical axis from the vertical axis is known as a tilted photograph.

Introduction To Aerial Photographs

Figure 6.3 Vertical Aerial Photograph

Figure 6.4 Vertical Aerial Photograph of Arneham, The Netherlands

(ii) Low Oblique: An aerial photograph taken with an intentional deviation

of 15° to 30° in the camera axis from the vertical axis is referred to as the low oblique photograph (Figures 6.5 and 6.6). This kind of photograph is often used in reconnaissance surveys.

73 Figure 6.5 Low-Oblique Photograph Figure 6.6 Low-Oblique Photograph of Arneham, The Netherlands

Practical Work in Geography

(iii)High Oblique: The high

oblique are photographs obtained when the camera axis is intentionally inclined

74

about 60° from the vertical axis (Figure 6.7). Such photography is useful in reconnaissance surveys.

Figure 6.7 High Oblique Photograph

Table 6.1 provides a comparison between vertical and oblique photographs. Table 6.1: Comparison between Vertical and Oblique Photographs Attributes

Vertical

Low Oblique

High Oblique

Optical Axis

Tilt < 3° i.e. exactly

Deviation is >300

Deviates by

or nearly

from the Vertical

axis > 30O

coincides with the

axis.

from vertical

Vertical axis.

axis.

Characteristics

Horizon does not

Horizon does

appear.

not appear.

appears.

Coverage

Small area

Relatively larger

Horizon Largest area

area Shape of the area

Square

Trapezoidal

Uniform, if the

Decreases from

Decreases

terrain is flat

foreground to

from the

background

foreground to

Trapezoidal photographed Scale

the background Difference in

Least

comparison to

Relatively

Greatest

greater

the map Advantages

Useful in

Reconnaissance

topographical

Survey

and thematic mapping

Illustrative

Introduction To Aerial Photographs

(b) Types of Aerial Photographs Based on Scale: The aerial photographs may also be classified on the basis of the scale of photograph into three types. (i) Large Scale Photographs: When the scale of an aerial photograph is 1 : 15,000 and larger, the photography is classified as large-scale photograph (Fig. 6.8).

Figure 6.8 1 : 5000 Photograph of Arnehem

(ii) Medium Scale Photographs: The aerial photographs with a scale ranging between 1 : 15,000 and 1 : 30,000 are usually treated as medium scale photographs (Fig. 6.9).

75 Figure 6.9 1 : 20,000 Photograph of Arnehem

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(iii) Small Scale

76

Photographs: The photographs with the scale being smaller than 1 : 30,000, are referred to as small scale photographs (Fig. 6.10).

Figure 6.10 1 : 40,000 Photograph of Arnehem

GEOMETRY OF AN AERIAL PHOTOGRAPH To understand the geometry of an aerial photograph, it is important to appreciate the orientation of the photograph with respect to the ground, i.e. the way the rays connect or ‘project’ onto the ground in relation to the ground representation (photograph or map). The following three examples of such projection would be useful in understanding the problem.

Parallel Projection: In this projection, the projecting rays are parallel but not necessarily perpendicular. The triangle ABC is projected on LL1 as triangle abc (Figure 6.11).

Figure 6.11 Parallel Projection

Introduction To Aerial Photographs

Orthogonal Projection: This is a special case of parallel projections. Maps are orthogonal projections of the ground. The advantage of this projection is that the distances, angles or areas on the plane are independent of the elevation differences of the objects. Figure 6.12 is an example of orthogonal projection where the projecting rays are perpendicular to the line LL1. Figure 6.12 Orthogonal projection

Central Projection: Figure 6.13 shows an example of Central Projection. The projecting rays Aa, Bb and Cc pass through a common point O, which is called the perspective Centre. The image projected by a lens is treated like a central projection. An aerial photograph, as discussed earlier is a central projection. In an absolutely vertical flat terrain the aerial photograph will be geometrically the same as the corresponding map of the area. However, because of the tilt of the photograph and relief variations of the ground photographed, an

Figure 6.13 Central Projection

aerial photograph differs geometrically from the map of the corresponding area. As shown in Figure 6.14, S is the camera lens centre. The bundle of light rays coming from the ground plane converge at this point and diverge from there towards the negative (photo) plane to form images of the objects. Thus, the central projection is characterised by the fact that all straight lines joining corresponding points, i.e. straight lines joining object points to their corresponding image points pass through one point. Figure 6.14 illustrates this relationship. Straight lines AAi, BBi, CCi and DDi join corresponding points on the ground photographed and the negative plane. For example, A on the ground and Ai on the negative plane (or ‘a’ on the positive plane) is a line joining corresponding points which pass through the camera lens centre. If we draw a perpendicular from S following the camera axis onto the negative plane, the point where this perpendicular meets the negative is known as the principal point (P in Fig. 6.14). If we extend the same line to the ground, it would meet the target (photographed

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ground) plane at PG, i.e. the ground principal point. Similarly, if we draw a vertical line (plumb line as indicated by the direction of gravity) through

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S, it will meet the photo negative at a point known as the nadir point and on the ground as the ground nadir point. Observe from figures 6.3, 6.5 and 6.7 that the plumb line and the camera axis are coincident for a vertical photograph while they are separable in case of an oblique or a tilted photograph. Thus in case of a vertical photograph, the principal and the nadir points also coincide with one another. For an oblique photograph, the angle between the camera axis and the plumb line is the tilt angle. Figure 6.14 shows both the positive and the negative planes of a vertical photograph. The geometry of the positive and the negative planes are identical.

Figure 6.14 Geometry of Vertical Photograph

It needs to be understood here that SP, i.e. the perpendicular distance between the camera lens and the negative plane is known as the focal length. On the other hand, SPG, i.e., the perpendicular distance between the camera lens and the ground photographed is known as the flying height.

Introduction To Aerial Photographs

DIFFERENCE

BETWEEN A

MAP

AND AN

AERIAL PHOTOGRAPH

A map cannot be directly traced out of an aerial photograph. The reason is that there is a basic difference in the planimetry (projection) and perspective of a map and an aerial photograph. The difference is given in Table 6.2.

Table 6.2: Difference between Maps and Aerial Photographs Aerial Photograph

Map

It is a central Projection.

It is an orthogonal Projection.

An aerial photograph is

A map is a geometrically correct

geometrically incorrect. The

representation of the part of the earth

distortion in the geometry is

projected.

minimum at the centre and increases towards the edges of the photographs. The scale of the photograph is

The scale of the map is uniform

not uniform.

throughout the map extent.

Enlargement/reduction does not

Enlargement/reduction of the maps

change the contents of the

involves redrawing it afresh.

photographs and can easily be carried out. Aerial photography holds good for

The mapping of inaccessible and

inaccessible and inhospitable areas.

inhospitable areas is very difficult and sometimes it becomes impossible.

Even vertical aerial photographs do not have a consistent scale unless they have been taken of a flat terrain. Aerial photographs need to be transformed from perspective view to the planimetric view before they can be used as map substitute. Such transformed photographs are known as orthophotos.

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SCALE OF AERIAL PHOTOGRAPH You are already familiar with the concept of a map scale (See Chapter 2).

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The concept of scale for aerial photographs is much the same as that of a map. Scale is the ratio of a distance on an aerial photograph the distance between the same two places on the ground in the real world. It can be expressed in unit equivalents like 1 cm= 1,000 km(or 12,000 inches) or as a representative fraction (1:100,000). Scale determines what objects would be visible, the accuracy of estimates and how certain features will appear. When conducting an analysis that is based on air photos, it will sometimes be necessary to make estimates regarding the number of objects, the area covered by a certain amount of material or it may be possible to identify certain features based on their length. To determine this dimension during air photo interpretation, it will be necessary to make estimates of lengths and areas, which require knowledge of the photo scale. There are three methods to compute the scale of an aerial photograph using different sets of information.

Method 1: By Establishing Relationship Between Photo Distance and Ground Distance : If additional information like ground distances of two identifiable points in an aerial photograph is available, it is fairly simple to work out the scale of a vertical photograph. Provided that the corresponding ground distances (Dg) are known for which the distances on an aerial photograph (Dp) are measured. In such cases, the scale of an aerial photograph will be measured as a ratio of the two, i.e. Dp/ Dg. Problem 6.1 The distance between two points on an aerial photograph is measured as 2 centimetres. The known distance between the same two points on the ground is 1 km. Compute the scale of the aerial photograph (Sp). Solution Sp = =

Therefore,

Dp : Dg 2 cm : 1 km

=

2cm : 1 x 100,000 cm

= =

1 : 100,000/2 = 50,000 cm 1 unit represents 50,000 units

Sp =

1 : 50,000

Introduction To Aerial Photographs

Method 2: By Establishing Relationship Between Photo Distance and Map Distance: As we know, the distances between different points on the ground are not always known. However, if a reliable map is available for the area shown on an aerial photograph, it can be used to determine the photo scale. In other words, the distances between two points identifiable both on a map and the aerial photograph enable us to compute the scale of the aerial photograph (Sp). The relationship between the two distances may be expressed as under : (Photo scale : Map scale) = (Photo distance : Map distance) We can derive Photo scale (Sp) = Photo distance (Dp) : Map distance (Dm) x Map scale factor (msf) Problem 6.2 The distance measured between two points on a map is 2 cm. The corresponding distance on an aerial photograph is 10 cm. Calculate the scale of the photograph when the scale of the map is 1: 50,000. Solution Sp

=

Dp : Dm x msf

Or

=

10 cm : 2 cm x 50,000

Or

=

10 cm : 100,000 cm

Or

=

1 : 100,000/10 = 10,000 cm

Or

=

1 unit represents 10,000 units

=

1 : 10,000

Therefore, Sp

Method 3: By Establishing Relationship Between Focal Length (f) and Flying Height (H) of the Aircraft : If no additional information is available about the relative distances on photograph and ground/map, we can determine the photo-scale provided the information about the

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focal length of the camera (f) and the flying height of the aircraft (H) are known (Fig. 6.15). The photo scale so determined could be more

Figure 6.15 Focal Length of the Camera (f) and Flying Height of the Aircraft (H)

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reliable if the given aerial photograph is truly vertical or near vertical and

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the terrain photographed is flat. The focal length of the camera (f) and the flying height of the aircraft (H) are provided as marginal information on most of the vertical photographs (Box 6.2). The Fig. 6.15 may be used to derive the photo-scale formula in the following way : Focal Length (f) : Flying Height(H) = Photo distance (Dp) : Ground distance (Dg) Problem 6.3 Compute the scale of an aerial photograph when the flying height of the aircraft is 7500m and the focal length of the camera is 15cm. Sp =

f:H

Or

Sp =

15 cm : 7,500 x 100 cm

Or Therefore,

Sp = Sp =

1 : 750,000/15 1 : 50,000

Box 6.2 Marginal Information given on Vertical Aerial Photographs

Fiducial Marks

3000m

Flying Height Indicator

793 B/5-23

Tilt Indicator Photo Specifications*

* 793 is a Photo Specification number maintained by the 73 APFPS Party of the Survey of India. B is the Flying Agency that carried out the present photography (In India three flying agencies are officially permitted to carry out aerial photography. They are the Indian Air Force, the Air Survey Company, Kolkata and the National Remote Sensing Agency, Hydrabad, identified on the aerial photographs as A, B and C respectively), 5 is the strip number and 23 is the photo number in strip 5.

Introduction To Aerial Photographs

EXERCISE Multiple Choice Questions 1. In which of the following aerial photographs the horizon appears? a. Vertical b. Near-vertical c. Low-oblique d. High-oblique 2. In which of the following aerial photographs the Nadir and the principle points coincide? a. Vertical b. Near-vertical c. Low-oblique d. High-oblique 3. Which type of the following projections is used in aerial photographs? a. Parallel b. Orthogonal c. Central d. None of the above.

Short Questions 1. State any three advantages that an aerial photograph offers over ground based observations. 2. How is an aerial photograph taken? 3. Present a concise account of aerial photography in India. 4. Answer the following questions in about 125 words : i) What are the two major uses of an aerial photograph? Elaborate. ii) What are the different methods of scale determination?

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Chapter 7 84

Introduction To Remote Sensing You have read about aerial photography in chapter 6. If you have carefully gone through its contents, you would have appreciated that it is an extension of the observation and recording capabilities of the human eyes. You may also have noticed that the photographic system utilises the same principles of observation and recording the objects of the earth’s surface, as being done by the eyes. However, both the human eyes and the photographic systems respond to light in a minute portion of the total energy received and responded by the objects’ surface. The present day remote sensing devices, on the other hand, react to much wider range of radiations reflected/emitted, absorbed and transmitted by all object surfaces at a temperature above 0 Kelvin (-273°C). The term remote sensing was first used in the early 1960s. Later, it was defined as the total processes used to acquire and measure the information of some property of objects and phenomena by a recording device (sensor) that is not in physical contact with the objects and phenomena in study. It can be noted from the above definition of remote sensing that it primarily involves an object surface, the recording device and the information carrying energy waves (Fig 7.1).

Information Carrying NATURAL SENSOR

Energy Waves

Figure 7.1 Conceptual Frame of Remote Sensing

OBJECT SURFACE

Introduction To Remote Sensing

Glossary Absorptance : The ratio of the radiant energy absorbed by a substance to the energy it receives. Band : The specific wavelength interval in the electromagnetic spectrum. Digital image : An array of digital numbers (DN) arranged in rows and columns, having the property of an intensity value and their locations. Digital Number : An intensity value of a pixel in a digital image. Digital Image Processing : The numerical manipulation of DN values for the purpose of extracting information about the phenomena of the surface they represent. Electromagnetic Radiation (EMR) : The Energy propagated through a space or a medium at a speed of light. Electromagnetic Spectrum : The continuum of EMR that ranges from short wave high frequency cosmic radiations to long wavelength low frequency radio waves. False Colour Composite (FCC) : An artificially generated colour image in which blue, green and red colours are assigned to the wavelength regions to which they do not belong in nature. For example, in standard a False Colour Composite blue is assigned to green radiations (0.5 to 0.6 µm), green is assigned to red radiations (0.6 to 0.7 µm and red is assigned to Near Infrared radiation (0.7 to 0.8 µm). Gray scale : A medium to calibrate the variations in the brightness of an image that ranges from black to white with intermediate grey values. Image :

The permanent record of a scene comprising of natural and man-made

features and activities, produced by photographic and non–photographic means. Scene : The ground area covered by an image or a photograph. Sensor : Any imaging or non–imaging device that receives EMR and converts it into a signal that can be recorded and displayed as photographic or digital image. Reflectance : The ratio of the radiant energy reflected by a substance to the energy it receives. Spectral Band : The range of the wavelengths in the continuous spectrum such as the green band ranges from 0.5 to .6 µ and the range of NIR band 0.7 to 1.1 µ.

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STAGES

IN

REMOTE SENSING

Figure 7.2 illustrates the processes used in remote sensing data

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acquisition. These basic processes that help in the collection of information about the properties of the objects and phenomena of the earth surface are as follows : (a) Source of Energy (sun/self-emission); (b) Transmission of energy from the source to the surface of the earth; (c) Interaction of energy with the earth’s surface; (d) Propagation of reflected/emitted energy through atmosphere; (e) Detection of the reflected/emitted energy by the sensor; (f) Conversion of energy received into photographic/digital form of data; (g) Extraction of the information contents from the data products; and (h) Conversion of information into Map/Tabular forms.

Figure 7.2 Stages in Remote Sensing Data Acquisition

a. Source of Energy: Sun is the most important source of energy used in remote sensing. The energy may also be artificially generated and used to collect information about the objects and phenomena such as flashguns or energy beams used in radar (radio detection and ranging).

b. Transmission of Energy from the Source to the Surface of the Earth: The energy that emanates from a source propagates between the source and the object surface in the form of the waves of

Introduction To Remote Sensing

energy at a speed of light (300,000 km per second). Such energy propagation is called the Electromagnetic Radiation (EMR). The energy waves vary in size and frequency. The plotting of such variations is known as the Electromagnetic Spectrum (Fig. 7.3). On the basis of the size of the waves and frequency, the energy waves are grouped into Gamma, X– rays, Ultraviolet rays, Visible rays, Infrared rays , Microwaves and Radio waves. Each one of these broad regions of spectrum is used in different applications. However, the visible, infrared and microwave regions of energy are used in remote sensing.

Figure 7.3 Electromagnetic Spectrum

c. Interaction of Energy with the Earth’s Surface: The propagating energy finally interacts with the objects of the surface of the earth. This leads to absorption, transmission, reflection or emission of energy from the objects. We all know that all objects vary in their composition, appearance forms and other properties. Hence, the objects’ responses to the energy they receive are also not uniform. Besides, one particular object also responds differently to the energy it receives in different regions of the spectrum (Fig. 7.5). For example, a fresh water body absorbs more energy in the red and infrared regions of the spectrum and appears dark/black in a satellite image whereas turbid water body reflects more in blue and green regions of spectrum and appears in light tone (Fig. 7.4).

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88

Figure 7.4 Spectral Signature of Soil, Vegetation and Water

Figure 7.5 IRS 1 C Band 1 Green (Left) and Band 4 IR Images of Sambhar Lake, Rajasthan

d. Propagation of Reflected/Emitted Energy through Atmosphere: When energy is reflected from objects of the earth’s surface, it re–enters into the atmosphere. You may be aware of the fact that atmosphere comprises of gases, water molecules and dust particles. The energy reflected from the objects comes in contact with the atmospheric constituents and the properties of the original energy get modified. Whereas the Carbon dioxide (CO2), the Hydrogen (H), and the water molecules absorb energy in the middle infrared region, the dust particles scatter the blue energy. Hence, the energy that is either absorbed or scattered by the atmospheric constituents never reaches to sensor placed onboard a satellite and the properties of the objects carried by such energy waves are left unrecorded.

Introduction To Remote Sensing

e. Detection of Reflected/Emitted Energy by the Sensor: The sensors recording the energy that they receive are placed in a near– polar sun synchronous orbit at an altitude of 700 – 900 km. These satellites are known as remote sensing satellites (e.g. Indian Remote Sensing Series). As against these satellites, the weather monitoring and telecommunication satellites are placed in a Geostationary position (the satellite is always positioned over its orbit that synchronises with the direction of the rotation of the earth) and revolves around the earth (coinciding with the direction of the movement of the earth over its axis) at an altitude of nearly 36,000 km (e.g. INSAT series of satellites). A comparison between the remote sensing and weather monitoring satellites is given in Box (7.1). Figure 7.6 shows the orbits of Sun-Synchronous and Geostationary satellites respectively. Box. 7.1 Comparison between Sun-Synchronous and Geostationary Satellites Orbital

Sun Synchronous

Geostationary

Characteristics

Satellites

Satellites

Altitude

700 – 900 km

@ 36,000 km

Coverage

810 N to 810 S

1/3rd of the Globe

Orbital period

@ 14 orbits per day

24 hours

Resolution

Fine

Coarse

(182 metre to 1 metre)

(1 km x 1 km)

Earth Resources

Telecommunication

Applications

and Weather monitoring

Uses

89 Figure 7.6 Orbit of Sun Synchronous (Left) and Geostationary (Right) Satellites

Remote sensing satellites are deployed with sensors which are capable of collecting the EMR reflected by the objects. We have seen in Chapter 6

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how the photographic camera obtains photographs at an instance of

90

exposure. However, the sensors used in remote sensing satellites possess a mechanism that is different from photographic camera in collecting and recording the information. The images so acquired by space-borne sensors are in digital format as against the photographic format obtained through a camera-based system.

f. Conversion of Energy Received into Photographic/ Digital Form of Data: The radiations received by the sensor are electronically converted into a digital image. It comprises digital numbers that are arranged in rows and columns. These numbers may also be converted into an analogue (picture) form of data product. The sensor onboard an earth-orbiting satellite electronically transmits the collected image data to an Earth Receiving Station located in different parts of the world. In India, one such station is located at Shadnagar near Hyderabad.

g. Extraction of Infor mation Contents from Data Products: After the image data is received at the earth station, it is processed for elimination of errors caused during image data collection. Once the image is corrected, information extraction is carried out from digital images using digital image processing techniques and from analogue form of data products by applying visual interpretation methods.

h. Conversion of Information into Map/Tabular Forms: The interpreted information is finally delineated and converted into different layers of thematic maps. Besides, quantitative measures are also taken to generate a tabular data.

SENSORS A sensor is a device that gathers electromagnetic radiations, converts it into a signal and presents it in a form suitable for obtaining information about the objects under investigation. Based upon the form of the data output, the sensors are classified into photographic (analogue) and non– photographic (digital) sensors. A photographic sensor (camera) records the images of the objects at an instance of exposure. On the other hand, a non–photographic sensor obtains the images of the objects in bit-by-bit form. These sensors are known as scanners. You have already read about the types and geometry

Introduction To Remote Sensing

of photographic cameras in Chapter 6. In the present chapter, we will confine ourselves to describe the non–photographic sensors that are used in satellite remote sensing.

Multispectral Scanners: In satellite remote sensing, the Multi Spectral Scanners (MSS) are used as sensors. These sensors are designed to obtain images of the objects while sweeping across the field of view. A scanner is usually made up of a reception system consisting of a mirror and detectors. A scanning sensor constructs the scene by recording a series of scan lines. While doing so, the motor device oscillates the scanning mirror through the angular field of view of the sensor, which determines the length of scan lines and is called swath. It is because of such reasons that the mode of collection of images by scanners is referred bit–by–bit. Each scene is composed of cells that determine the spatial resolution of an image. The oscillation of the scanning mirror across the scene directs the received energy to the detectors, where it is converted into electrical signals. These signals are further converted into numerical values called Digital Number (DN Values) for recording on a magnetic tape. The Multi-Spectral Scanners are divided into the following types: (i) Whiskbroom Scanners (ii) Pushbroom Scanners (i) Whiskbroom Scanners : The whiskbroom scanners are made up of a rotating mirror and a single detector. The mirror is so oriented that when it completes a rotation, the detector sweeps across the field of view

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7.7 Whiskbroom Scanners

7.8 Pushbroom Scanners

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between 90° and 120° to obtain images in a large number of narrow

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spectral bands ranging from visible to middle infrared regions of the spectrum. The total extent of the oscillating sensor is known as the Total Field of View (TFOV) of the scanner. While scanning the entire field, the sensor’s optical head is always placed at a particular dimension called the Instantaneous Field of View (IFOV). Figure 7.7 depicts the scanning mechanism of whiskbroom scanners. (i) Pushbroom Scanners: The pushbroom scanners consist of a number of detectors which are equivalent to the number obtained by dividing the swath of the sensor by the size of the spatial resolution (Fig. 7.8). For example, the swath of High Resolution Visible Radiometer – 1 (HRVR – 1) of the French remote sensing satellite SPOT is 60 km and the spatial resolution is 20 metres. If we divide 60 km x 1000 metres/20 metres, we get a number of 3000 detectors that are deployed in SPOT HRV – 1 sensor. In pushbroom scanner, all detectors are linearly arrayed and each detector collects the energy reflected by the ground cell (pixel) dimensions of 20 metres at a nadir’s view.

RESOLVING POWERS OF THE SATELLITES In satellite remote sensing, the sun-synchronous polar orbit enables the collection of images after a pre-determined periodical interval referred to as the temporal resolution or the revisit time of the satellite over the same area of the earth surface. Fig. 7.9 illustrates the two images acquired over two different periods in time for the same area enabling to study and record the changes that take place with respect to the types of vegetation in Himalayas. In another example, Fig. 7.10 (a and b) shows the images acquired before and after the tsunami in the Indian Ocean. The image acquired in June 2004 clearly shows the undisturbed topography of Banda Aceh in Indonesia, whereas the post tsunami image acquired immediately after tsunami reveals the damages that were caused by the tsunami.

Introduction To Remote Sensing

Figure 7. 9 Images of Himalayas and Northern Indian Plain by IRS Satellite taken in May (Left) and November (Right) show differences in the types of vegetation. The red patches in May image refer to Coniferous vegetation. In November image the additional red patches refer to Deciduous plants and the light red colour is related to the crops.

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Figure 7.10 (a) Pre-tsunami Image acquired in June 2004

Figure 7.10 (b) Post-tsunami image acquired in December, 2004

Introduction To Remote Sensing

SENSOR RESOLUTIONS Remote sensors are characterised by spatial, spectral and radiometric resolutions that enable the extraction of useful information pertaining to different terrain conditions.

(i) Spatial Resolution: You must have seen some people using spectacles while reading a book or newspaper. Have you ever thought as to why they do so. It is simply because of the fact that resolving power of their eyes to differentiate two closed spaced letters in a word is unable to identify them as two different letters. By using positive spectacles they try to improve their vision as well as the resolving power. In remote sensing, the spatial resolution of the sensors refers to the same phenomena. It is the capability of the sensor to distinguish two closed spaced object surfaces as two different object surfaces. As a rule, with an increasing resolution the identification of even smaller object surfaces become possible.

(ii) Spectral Resolution: It refers to the sensing and recording power of the sensor in different bands of EMR (Electromagnetic radiation). Multispectral images are acquired by using a device that disperses the radiation received by the sensor and recording it by deploying detectors sensitive to specific spectral ranges. The principles in obtaining such images is the extension of the dispersion of light in nature resulting in the appearance of the ‘rainbow” and the use of prism in the lab (Box 7.2). The images obtained in different bands show objects response differently as discussed in Para 3 of the stages in remote sensing data acquisition. Fig. 7.11 illustrates images acquired in different spectral regions by IRS P - 6 (Resource sat - 1) showing strong absorption properties of fresh water in band 4 (Infrared) and mixed strong reflectance in band 2 (green) by dry surfaces (Fig. 7.11).

(iii) Radiometric Resolution: It is the capability of the sensor to discriminate between two targets. Higher the radiometric resolution, smaller the radiance differences that can be detected between two targets. The spatial, spectral, and radiometric resolutions of some of the remote sensing satellites of the world are shown in Table 7.1.

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Table 7.1 Spatial, Spectral and Radiometric Resolution of Landsat, IRS and SPOT Sensors

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Satellite/Sensor

Spatial Resolution

Number of

Radiometric Range

(in metres)

Bands

(Number of Grey Level Variations)

Landsat MSS (USA)

80.0 x 80.0

4

0 - 64

IRS LISS – I (India)

72.5 x 72.5

4

0 - 127

IRS LISS – II (India)

36.25 x 36.25

4

0 - 127

Landsat TM (USA)

30.00 x 30.00

4

0 - 255

IRS LISS III (India)

23.00 x 23.00

4

0 - 127

SPOT HRV - I (France)

20.00 x 20.00

3

0 - 255

SPOT HRV – II (France) 10.00 x 10.00

1

0 - 255

IRS PAN (India)

1

0 - 127

5.80 x 5.80

Box : 7.2

RAINBOW (Natural Dispersion of Light) Dispersion of Light (The principle that is utilised in obtaining Multispectral Images) The overall mechanism of obtaining images in a number of bands derives strength from the principle of the dispersion of light. You must have seen the rainbow. It is formed through a natural process of dispersion of light rays through

PRISM (Artificial Dispersion of Light)

water molecules present in the atmosphere. The same phenomena may be experimented by putting a beam of light at one side of a prism. At the other side of the prism you may notice the dispersion of energy into seven colours that form white light.

Introduction To Remote Sensing

Figure 7. 11 IRS P - 6 (Resourcesat - 1) Images of Parts of Najafgarh, Delhi, 03 June 2005

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DATA PRODUCTS We have seen that the electromagnetic energy may be detected either

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photographically or electronically. The photographic process uses light sensitive film to detect and record energy variations (Refer Chapter 6). On the other hand, a scanning device obtains images in digital mode. It is important to distinguish between the terms – images and photographs. An image refers to pictorial representation, regardless of what regions of energy have been used to detect and record it. A photograph refers specifically to images that have been recorded on photographic film. Hence, it can be said that all photographs are images, but all images are not photographs. Based upon the mechanism used in detecting and recording, the remotely sensed data products may be broadly classified into two types : ’

Photographic Images

’

Digital Images

Photographic Images: Photographs are acquired in the optical regions of electromagnetic spectrum, i.e. 0.3 – 0.9 µm. Four different types of light sensitive film emulsion bases are used to obtain photographs. These are black and white, colour, black and white infrared and colour infrared. However, in aerial photography black and white film is normally used. Photographs may be enlarged to any extent without loosing information contents or the contrast.

Digital Images: A digital image consists of discrete picture elements called pixels. Each one of the pixels in an image has an intensity value and an address in two-dimensional image space. A digital number (DN) represents the average intensity value of a pixel. It is dependent upon the electromagnetic energy received by the sensor and the intensity levels used to describe its range. In a digital image, the reproduction of the details pertaining to the images of the objects is affected by the size of the pixel. A smaller size pixel is generally useful in the preservation of the scene details and digital representation. However, zooming of the digital image beyond certain extent produces loss of information and the appearance of pixels only. Using a digital image processing algorithms, the digital numbers representing their intensity level in an image may be displayed (Fig. 7.12).

Introduction To Remote Sensing

Figure 7.12 Digital Image (top) and Part of it zoomed showing Pixel’s brightness (left) and the associated Digital Numbers (right)

INTERPRETATION OF SATELLITE IMAGERIES The data obtained from the sensors is used for information extraction related to the forms, and patterns of the objects and phenomena of the earth’s surface. We have seen that different sensors obtain photographic and digital data products. Hence, the extraction of both qualitative and quantitative properties of such features could be carried out using either visual interpretation methods or digital image processing techniques. The visual interpretation is a manual exercise. It involves reading of the images of objects for the purpose of their identification. On the other hand, digital images require a combination of hardware and software to extract the desired information. It would not be possible to deliberate upon the digital image processing techniques under the constraints of time, equipments and accessories. Hence, only visual interpretation methods would be discussed.

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Elements of Visual Interpretation Whether we are conscious of it or not we use the form, size, location of the

100 100

objects and their relationships with the surrounding objects to identify them in our day-to-day life. These characteristics of objects are termed as elements of visual interpretation. We can further group the characteristics of the objects into two broad categories, i.e. image characteristics and terrain characteristics. The image characteristics include tone or colour in which objects appear, their shape, size, pattern, texture and the shadow they cast. On the other hand, location and the association of different objects with their surrounding objects constitute the terrain characteristics. 1. Tone or Colour: We know that all objects receive energy in all regions of spectrum. The interaction of EMR with the object surface leads to the absorption, transmittance and reflection of energy. It is the reflected amount of the energy that is received and recorded by the sensor in tones of grey, or hues of colour in black and white, and colour images respectively. The variations in the tone or the colour depend upon the orientation of incoming radiations, surface properties and the composition of the objects. In other words, smooth and dry object surfaces reflect more energy in comparison to the rough and moist surfaces. Besides, the response of the objects also varies in different regions of the spectrum (Refer para ‘C – Stages in remote sensing data acquisition’). For example, healthy vegetation reflects strongly in the infrared region because of the multiple-layered leaf structure and appears in a light tone or bright red

7.13 (a) Turbid river

7.13 (b) River with fresh water

Introduction To Remote Sensing

colour in standard false colour composite and the scrubs appear in greyish red colour). Similarly, a fresh water body absorbs much of the radiations received by it and appears in dark tone or black colour, whereas the turbid water body appears in light tone or light bluish colour in FCC due to mixed response shown by the water molecules as well as suspended sand particles (Figures 7.13 a and b). The colours in which different features of the earth’s surfaces are recorded in remote sensing images are given in Table 7.2. Table 7.2: Colour Signatures on Standard False Colour Composite of Earth Surface Features S. No.

Earth Surface Feature

1.

Healthy Vegetation and Cultivated Areas

Colour(In Standard FCC)

Evergreen

Red to magenta

Deciduous Scrubs

Brown to red Light brown with red patches

2.

3.

4.

Cropped land Fallow land

Bright red Light blue to white

Waterbody Clear water

Dark blue to black

Turbid waterbody

Light blue

Built – up area High density

Dark blue to bluish green

Low density

Light blue

Waste lands/Rock outcrops Rock outcrops Sandy deserts/River sand/

Light brown Light blue to white

Salt affected Deep ravines Shallow ravines

Dark green Light green

Water logged/Wet lands

Motelled black

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102 102

2. Texture: The texture refers to the minor variations in tones of grey or hues of colour. These variations are primarily caused by an aggregation of smaller unit features that fail to be discerned individually such as high density and low density residential areas; slums and squatter settlements; garbage and other forms of solid waste; and different types of crops and plants. The textural differences in the images of certain objects vary from smooth to coarse textures (Fig. 7.14 a and b). For example, dense residential areas in a large city form fine texture due to the concentration of the houses in a smaller area and the low-density residential areas produce a coarse texture. Similarly, in high resolution images the sugarcane or millet plants produce coarse texture in comparison to the fine texture of rice or wheat plants. One can also notice the coarse texture in the images of scrubbed lands if compared with the fine texture of lush green evergreen forests.

Figure 7.14 (a) Coarse texture image of

Figure 7.14 (b) Fine texture of cropped land

mangroves

3. Size: The size of an object as discerned from the resolution or scale of an image is another important characteristic of individual objects. It helps in distinctively identifying the industrial and industrial complexes with residential dwellings (Fig. 7.15), stadium in the heart of the city with the brick kilns at an urban fringe, size and hierarchy of the settlements, etc. 4. Shape: The general form and configuration or an outline of an individual object provides important clues in the interpretation of remote sensing images. The shape of some of the objects is so distinctive that make them easy to identify. For example, the shape of the Sansad Bhawan is typically distinct from many other built-up features. Similarly, a railway line can be readily distinguished from a road due to its long continuous linearity in shape with gradual change in its course (Figure 7.16). The

Introduction To Remote Sensing

(a) Parts of Kolkata

(b) Parts of Varanasi

Figure 7.15 Variations in size between institutional buildings and residential areas may be distinctly identified in the images of parts of Kolkata (a) and Varanasi (b)

shape also plays a deciding role in the identity of religious places such as mosques and temples as distinct features. 5. Shadow: Shadow of an object is a function of the sun’s illumination angle and the height of the object itself. The shape of some of the objects is so typical that they could not be identified without finding out the length of the shadow they cast. For example, the Qutub Minar located in Delhi, minarets of mosques, overhead water tanks, electric or telephone lines, and similar features can only be identified using their shadow. Shadow also adversely affects the identifiability of the objects in city centres as it produces a dark tone, which dominates the original tone or colour of the features lying under the shadow of tall buildings. It may , however, be noted that the shadow as an element of image interpretation is of less use in

103 103

satellite images. However, it serves a useful purpose in large-scale aerial photography. 6. Pattern: The spatial arrangements of many natural and man–made features show repetitive

Figure 7.16 Curvilinear shape of the Railway Tract is Distinctly different from Sharp Bending Roads.

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appearance of forms and relationships. The arrangements can easily be

104 104

identified from the images through the utilisation of the pattern they form. For example, planned residential areas with the same size and layout plan of the dwelling units in an urban area can easily be identified if their pattern is followed (Figure 7.17). Similarly, orchards and plantations produce arrangements of the same type of plants with uniform inter – plant distances. A distinction can also be made between various types of drainage or settlements if their pattern is properly studied and recognised.

Figure 7.17

Planned residential areas are easily identifiable using the pattern they form

7. Association: The association refers to the relationship between the objects and their surroundings along with their geographical location. For example, an educational institution always finds its association with its location in or near a residential area as well as the location of a playground within the same premises. Similarly, stadium, race course and golf course holds good for a large city, industrial sites along highway at the periphery of a growing city, and slums along drains and railway lines.

Introduction To Remote Sensing

EXERCISE 1. Choose the right answer from the four alternatives given below (i) Remote sensing of objects can be done through various means such as A. remote sensors, B. human eyes and C. photographic system. Which of the following represents the true order of their evolution. (a) ABC (b) BCA (c) CAB (d) None of the above (ii) Which of the following regions of Electromagnetic spectrum is not used in satellite remote sensing. (a) Microwave region (b) Infrared region (c) X - rays (d) Visible region (iii) Which of the following is not used in visual interpretation technique ? (a) Spatial arrangements of objects (b) Frequency of tonal change on the image (c) Location of objects with respect to other objects (d) Digital image processing 2. Answer the following questions in about 30 words. (i) Why is remote sensing a better technique than other traditional methods? (ii) Differentiate between IRS and INSAT series of satellites. (iii) Describe in brief the functioning of pushbroom scanner. 3. Answer the following questions in about 125 words. (i) Describe the operation of a whiskbroom scanner with the help of a diagram. Explain how it is different from pushbroom scanner. (ii) Identify and list the changes that can be observed in the vegetation of Himalayas (Fig.7.9).

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ACTIVITY Identify various features marked on IRS IC LISS III imagery shown

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below. Draw clues from the description of the elements of image interpretation discussed and the colours in which various objects appear on a standard alse Colour Composite.

Weather Instruments, Maps and Charts

Chapter 8

Weather Instruments, Maps and Charts Weather denotes the atmospheric conditions of weather elements at a particular place and time. The weather elements include temperature, pressure, wind, humidity and cloudiness. Each day weather maps are prepared for that day by the Meteorological Department from the data obtained from observations made at various weather stations across the world. In India, weather-related information is collected and published under the auspices of the Indian Meteorological Department, New Delhi, which is also responsible for weather forecasting.

Indian Meteorological Department The Indian Meteorological Department (IMD) was established in 1875, with its headquarters at Calcutta. The IMD headquarters are presently located at New Delhi.

Weather forecasts help in taking safety measures in advance in case of the likelihood of bad weather. Predicting weather a few days in advance may prove very useful to farmers and to the crew of ships, pilots, fishermen, defence personnel, etc. Glossary 1. Weather :

The condition of the atmosphere at a given place and time

with respect to atmospheric pressure, temperature, humidity, precipitation, cloudiness and wind. These factors are known as weather elements. 2. Weather Forecast : Prediction with a reasonable amount of certainty about the conditions of weather that would prevail in the coming 12 to 48 hours in a certain area.

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WEATHER OBSERVATIONS Globally, meteorological observations are recorded at three levels, viz.

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surface observatories, upper air observatories and space-based observation platforms. The World Meteorological Organization (WMO), a specialised agency of the United Nations, coordinates these observations.

SURFACE OBSERVATORIES A typical surface observatory has instruments for measuring and recording weather elements like temperature (maximum and minimum), air pressure, humidity, clouds, wind and rainfall. Specialised observatories also record elements like radiation, ozone atmospheric trace gases, pollution and atmospheric electricity. These observations are taken all over the globe at fixed times of the day as decided by the WMO and the use of instruments are made conforming to international standards, thus making observations globally compatible. In India, meteorological observations are normally classified into five categories depending upon their instruments and the number of daily observations taken. The highest category is Class-I. Typical instrumental facility available in a Class-I observatory consists of the following: “ Maximum and minimum thermometers “ Anemometer and wind vane “ Dry and Wet bulb thermometer “ Rain gauge “ Barometer

Observations are taken in these observatories normally at 00,03,06,09,12,15,18,21 hours (Greenwich Mean Time) around the globe. However, for logistic reasons, some of the observatories take limited number of daily observations upper air observation during daytime only.

SPACE-BASED OBSERVATIONS Weather satellites make comprehensive and large-scale observations of different meteorological elements at the ground level as well in the upper layers of the atmosphere. The geo-stationary satellites provide space-based observations about weather conditions (refer to Chapter 7). For example, The Indian National Satellite (INSAT) provides valuable observations of temperature, cloud cover, wind and associated weather phenomena.

Weather Instruments, Maps and Charts

WEATHER INSTRUMENTS Various instruments are used for measuring different weather phenomena. Some of the common but important weather instruments are listed below.

Thermometer Thermometer is used to measure air temperature. Most thermometers are in the form of a narrow closed glass tube with an expanded bulb at one end. The bulb and the lower part of the tube are filled with liquid such as mercury or alcohol. Before the other end is sealed off, the air in the tube is released by heating it. The bulb of the thermometer in contact with the air gets heated or cooled, as the case may be, as a result of which the mercury in the bulb rises or falls. A scale is marked on the glass tube

Figure 8.1 Maximum Thermometer

and readings are taken from there. The two most common scales used in thermometers are Centigrade and the Fahrenheit. On the Centigrade thermometer, the temperature of melting ice is marked 00C and that of boiling water as 1000C, and the interval between the two is divided into 100 equal parts. On the Fahrenheit thermometer, the freezing and boiling points of water are graduated as 320F and 2120F respectively. While the maximum thermometer and minimum thermometer are used to measure the air temperature, the dry bulb and the wet bulb thermometers are used to determine the humidity in the air. A set of these thermometers is kept in the Stevenson Screen (Box 8.2). The maximum thermometer is designed to record the highest temperature during a day. As the temperature increases, the mercury moves up into the tube; however, as the mercury cools, it cannot move downwards because of a constriction in the tube. It must be reset again to bring it down. The minimum thermometer records the lowest reading Figure 8.2 Minimum Thermometer

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STEVENSON SCREEN

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The Stevenson screen is designed to protect thermometers from precipitation and direct sunlight while allowing air to circulate freely around them. It is made from wood with louvered sides to allow free and even flow of air. It is painted white to reflect radiation. It stands on four legs and is about 3 feet 6 inches above the level of the ground. The legs must be sufficiently rigid and be buried sufficiently in the ground to prevent shaking. The front panel is hinged at the bottom to form a door, which allows for maintenance and reading of the thermometers. The door of Stevenson screen is always towards the north in the northern hemisphere and towards the south in the southern hemisphere because direct sunrays also affect mercury. The purpose of the Stevenson screen is to create a uniform temperature enclosure that closely represents the same temperature as the air outside.

in a day. In this thermometer, alcohol is used in place of mercury. When the temperature decreases, the metal pin in the tube goes down and strikes at the minimum temperature. (Fig. 8.1 Maximum and Fig. 8.2 Minimum Thermometers). The dry bulb and wet bulb thermometers are used for measuring humidity in the air (Fig. 8.3). The dry bulb and wet bulb thermometers are two identical thermometers fixed to a wooden frame. The bulb of the dry thermometer is kept uncovered and is exposed to the air while the bulb of the wet bulb thermometer is wrapped up with a piece of wet muslin, which is kept continuously moist by dipping a strand of it into a small vessel of distilled water. The evaporation from the wet bulb lowers its temperature. Figure 8.3 Wet and Dry Bulb Thermometer

Weather Instruments, Maps and Charts

Dry bulb readings are not affected by the amount of water vapour present in the air, but the wet bulb readings vary with it since the rate of evaporation is dependent upon the amount of water vapour present in the air. The greater the humidity in the air, the slower the rate of evaporation and hence, the difference between the readings of the dry bulb and wet bulb will be small. On the other hand, when the air is dry, the evaporation from the surface of the wet bulb is rapid, which would lower its temperature and the difference between the two readings would be larger. Hence, the difference of the readings of the dry bulb and the wet bulb thermometers determines the state of the atmosphere with regard to its humidity. The larger the difference, the more arid is the air.

Barometer The air around us has weight, and it exerts great pressure on the earth’s surface. At the sea level, under normal conditions, the pressure of air is 1.03 kg per square centimetre. Due to constant movement of air, change in temperature and variation in its vapour content, the weight of the air changes continuously with time and place. The instrument used to measure atmospheric pressure is called a barometer. The most commonly used barometers are the mercury

barometer,

aneroid

barometer and barographs. The unit of measurement is in the millibar. Mercury barometer is an accurate instrument and is used as a standard. In it the atmospheric pressure of any place is balanced against the weight of a column of mercury in an inverted glass tube. The principle of a mercurial

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barometer can be explained by a simple experiment (Fig. 8.4). Take a thick glass tube of uniform length about a meter long and fill it with mercury.

Figure 8.4 Mercury Barometer

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Close the mouth of the tube with a finger, then invert and immerse its open end in a cup of mercury without allowing

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air to enter into the tube and then remove the finger. The mercury will flow out of the tube into the cup and stand at a definite height above the level of the liquid in the cup. This is because the weight of the column of the mercury in the tube, above the surface of the mercury in the cup, is balanced by the weight of the air column of an indefinite height exerted as pressure Figure 8.5 Aneroid Barometer

upon an equal cross-section of the liquid surface. The height of the column of mercury in the tube, therefore, becomes

the measure of the pressure of air. Aneroid barometer gets its name from the Greek work, aneros (a- ‘not’, neros – ‘moisture’, meaning without liquid). It is a compact and portable instrument. It consists of a corrugated metal box made up of a thin alloy, sealed completely and made airtight after partial exhaustion of air. It has a thin flexible lid, which is sensitive to changes of pressure. (Fig. 8.5) As the pressure increases, the lid is pressed inward, and this, in turn, moves a system of levers connected to a pointer, which moves clockwise over the graduated dial and gives higher reading. When the pressure decreases, the lid is pushed outward and the pointer moves counter clockwise, indicating lower pressure. Barograph works on the principle of aneroid barometer. There are a number of vacuum boxes placed one above the other so that the displacement is large. A system of levers magnifies this movement which is recorded by a pen on a paper attached to a rotating drum. The readings of a barograph are not always accurate, and therefore, they are standardised by comparing them with a mercury barometer reading.

Wind Vane Wind vane is a device used to measure the direction of the wind. The wind vane is a lightweight revolving plate with an arrowhead on one end and two metal plates attached to the other end at the same angle. This revolving plate is mounted on a rod in such a manner that it is free to rotate on a horizontal plane. It responds

Weather Instruments, Maps and Charts

Figure 8.6 Wind Vane Figure 8.7 Rain Gauge

even to a slight blow of wind. The arrow always points towards the direction from which the wind blows. (Fig. 8.6)

Rain Gauge The amount of rainfall is measured with the help of a rain gauge. The rain gauge consists of a metal cylinder on which a circular funnel is fitted. The diameter of the funnel’s rim is normally 20 cm. The rain drops are collected and measured in a measuring glass. Normally, rainfall is measured in the units of millimetres or centimetres. Snow is also measured in a similar manner by turning it into liquid form (Fig. 8.7).Table 8.1: Instruments

Instruments for Measuring Weather Elements S. No

Element

Instrument

Unit

1

Temperature

Thermometer °C/°F

2

Atmospheric Pressure Barometer

Millibars

3 4

Wind (Direction) Wind (Velocity)

Wind Vane Anemometer

Cardinal points Km/hr

5

Rainfall

Rain Gauge

mm/cm

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WEATHER MAPS

AND

CHARTS

Weather Maps: A weather map is the representation of weather

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phenomena of the earth or a part of it on a flat surface. It depicts conditions associated with different weather elements such as temperature, rainfall, sunshine and cloudiness, direction and velocity of winds, etc. on a particular day. Such observations being taken at fixed hours are transmitted by code to the forecasting stations. The central office keeps a record of the observations, which forms the basis for making a weather map. The upper air observations which are procured from hill stations, aeroplanes, pilot balloons, etc. are plotted separately. Since the inception of the Indian Meteorological Department, the weather maps and charts are prepared regularly. Meteorological observatories transmit the data to the Central Observatory at Pune twice a day. Data is also collected on ships plying on the Indian seas. A good progress has been made in the field of weather forecasting and observation with the establishment of weather observatories in Antarctica, the International Indian Ocean Expedition, and the launching of rockets and weather satellites.

Weather Charts: The data received from various weather observatories are in plenty and detailed. As such, they cannot be incorporated in one single chart unless the coding designed to give the economy of expression is used. These are called synoptic weather charts and the codes used are called meteorological symbols. Weather charts provide the primary tools for weather forecasting. They help in locating and identifying different air masses, pressure systems, fronts and areas of precipitation.

WEATHER SYMBOLS The messages received from all the observatories are plotted on the map using weather symbols standardised by the World Meteorological Organisation and the National Weather Bureaus. (Figures 8.8 and 8.9) To facilitate the interpretation of the plots, each element occupies a fixed position to the station circle as given in Figures 8.8 and 8.9.

Weather Instruments, Maps and Charts

Figure 8.8 Meteorological Symbols (Approved by the International Meteorological Organisation, Warsaw, 1935)

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Light breeze Gentle breeze Moderate breeze Fresh breeze Strong breeze

Moderate gale Fresh gale Strong gale Whole gale Storm Hurricane

3

4

5

6

7

8

9

10

11

12

Light air

1

Arrow

Figure 8.9 Wind Speed and Common Effects

118 plus

103-117

89-102

75-88

62-74

50-61

Most destructive.

Very rarely experienced, accompanied by widespread damage.

Seldom experienced inland; trees uprooted, considerable structural damage occurs.

Slight structural damage occurs (chimney pots and slates removed.)

Breaks twigs off trees; generally impedes progress.

Whole tree in motion, inconvenience felt when walking against wind.

Large branches in motion; whistling heard in telegraph wires umbrellas used with diffiuclty.

Small tree in leaf begin to sway, crested wavelets from an inland waters.

29-38 39-49

Raises dust and loose papers, small branches are moved.

Leaves and small twigs in constant motion, wind extends light flag.

12-19 20-28

Wind felt on face; leaves rustle; ordinary vane move by winds.

Direction of wind shown by smoke drift, but not wind vanes.

1-5 6-11

Calm, Smoke rise vertically.

Common effects

0

Speed km/hr

116

2

Calm

Wind

0

Beaufort No.

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Weather Instruments, Maps and Charts

Mapping the Climatic Data Much of the climatic data is represented by line symbols. The most common of these are the isometric lines. These lines are depicted on the map as isopleths. The Isopleth can be interpolated for places having the same mean values of temperature, rainfall, pressure, sunshine, clouds, etc. Some of these lines and their uses are mentioned below: Isobars : Lines connecting places of equal air pressure. Isotherms :

Lines connecting places of equal temperature.

Isohyets :

Lines connecting places of equal amount of rainfall over a given period of time.

Isohels :

Lines connecting places of same mean daily duration of

Isonephs :

sunshine. Lines connecting places of same mean value of cloud cover.

Weather Map Interpretation On the basis of the above information, we can analyse a weather map and understand the general pattern of weather conditions prevailing in different parts of the country. In Fig. 8.10 the general weather conditions prevailing in India during the month of May are plotted. There is a general increase of pressure towards the north and north-east. Two low-pressure centres can be identified with one over Rajasthan and the other over the Bay of Bengal. The low pressure centre is well developed over the Bay of Bengal marked by concentric isobars, with the lowest air pressure being 996 mb. The southern part of India has overcast skies. The central part of India, on the other hand, has generally clear skies. In the southern part of the eastern coast, the winds are mostly from the land to the sea, flowing in an anti-clockwise direction. Also, read Fig. 8.13 and find out the temperature and pressure conditions in July. In Figures 8.11 and 8.12, the general weather conditions during winters in the month of January are plotted. There is a general increase of pressure towards the north from south. Most of the country has clear skies with a high-pressure region developing to the eastern side of India. The highest pressure isobar of 1018 mb passes through Rajasthan.

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Figure 8.10 Indian Weather Map (for the month of May)

Weather Instruments, Maps and Charts

119

Figure 8.11 Indian Weather Map (for the month of January)

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120

Figure 8.12 India - Mean Pressure and Temperature (January)

Weather Instruments, Maps and Charts

121

Figure 8.13 Mean Pressure and Temperature (July)

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EXERCISES

122

1. Choose the right answer from the four alternatives given below. (i) Which department prepares the weather map of India for each day? (a) The World Meteorological Organisation (b) The Indian Meteorological Department (c) The Survey of India (d) None of these (ii) Which two liquids are used in maximum and minimum thermometers? (a) Mercury and water (b) Water and alcohol (c) Mercury and alcohol (d) None of these (iii) Lines connecting the places of equal pressure are called (a) Isobars (b) Isohyets (c) Isotherms (d) Isohels The primary tool for weather forecasting is (iv) (a) Thermometer (b) Barometer (c) Maps (d) Weather charts (v) If there is more humidity in the air, the difference between the readings of a dry bulb and a wet bulb will be (a) Less (b) More (c) Equal (d) None of these 2. Answer the following questions in about 30 words. (i) What are the basic elements of weather? (ii) What is a weather chart? (iii) Which instruments are normally available in Class-I observatory to measure the weather phenomena? (iv) What are Isotherms?

Weather Instruments, Maps and Charts

(v) Which meteorological symbols are used to mark the following on a weather map? a) Rain b) Mist c) Sunshine d) Lightning e) Overcast Sky 3. Answer the following question in not more than 125 words. Discuss how weather maps and charts are prepared and how they are useful to us.

MAP READING Study the Figures 8.12 and 8.13 and answer the following questions. (a) Which seasons are shown in these maps? (b) What is the value of the highest isobar in Figure 8.12 and through which part of the country does it pass? (c) What are the values of the highest and the lowest isobars in Figure 8.13 and where are they located? (d) What are the patterns of temperature distribution in both the maps? (e) In which parts do you see the highest and the lowest mean temperature in Figure 8.12? (f) What relationship do you see between the distribution of temperature and pressure in both the maps?

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Contents FOREWORD

iii

CHAPTER 1 Data – Its Source and Compilation

1 – 12

CHAPTER 2 Data Processing

13 – 31

CHAPTER 3 Graphical Representation of Data

32– 54

CHAPTER 4 Use of Computer in Data Processing and Mapping

55 – 70

CHAPTER 5 Field Surveys

71 – 84

CHAPTER 6 Spatial Information Technology APPENDIX GLOSSARY

85 – 100 101 – 105 106

You must have seen and used various forms of data. For example, at the end of almost every news bulletin on Television, the temperatures recorded on that day in major cities are displayed. Similarly, the books on the Geography of India show data relating to the growth and distribution of population, and the production, distribution and trade of various crops, minerals and industrial products in tabular form. Have you ever thought what they mean? From where these data are obtained? How are they tabulated and processed to extract meaningful information from them ? In this chapter, we will deliberate on these aspects of the data and try to answer these many questions.

What is Data? The data are defined as numbers that represent measurements from the real world. Datum is a single measurement. We often read the news like 20 centimetres of continuous rain in Barmer or 35 centimetres of rain at a stretch in Banswara in 24 hours or information such as New Delhi – Mumbai distance via Kota – Vadodara is 1385 kilometres and via Itarsi - Manmad is 1542 kilometres by train. This numerical information is called data. It may be easily realised that there are large volume of data available around the world today. However, at times, it becomes difficult to derive logical conclusions from these data if they are in raw form. Hence, it is important to ensure that the measured information is algorithmically derived and/or logically deduced and/or statistically calculated from multiple data. Information is defined as either a meaningful answer to a query or a meaningful stimulus that can cascade into further queries.

Need of Data Maps are important tools in studying geography. Besides, the distribution and growth of phenomena are also explained through the data in tabular form. We know that an interelationship exists between many phenomena over the surface of the earth. These interactions are influenced by many variables which can be

explained best in quantitative terms. Statistical analysis of those variables has become a necessity today. For example, to study cropping pattern of an area, it is necessary to have statistical information about the cropped area, crop yield and production, irrigated area, amount of rainfall and inputs like use of fertiliser, insecticides, pesticides, etc. Similarly, data related to the total population, density, number of migrants, occupation of people, their salaries, industries, means of transportation and communication is needed to study the growth of a city. Thus, data plays an important role in geographical analysis.

Presentation of the Data

P ractical W ork in Geography, P art-II Work Part-II

2

You might have heard the story of a person who was travelling with his wife and a five-year old child. On his way, he had to cross a river. Firstly, he fathomed the depth of the river at four points as 0.6, 0.8, 0.9 and 1.5 metres. He calculated the average depth as 0.95 metres. His child’s height was 1 metre. So, he led them to cross the river and his child drowned in the river. On the other bank, he sat pondering: “Lekha Jokha Thahe, to Bachha Dooba Kahe ?” (Why did the child drown when average depth was within the reach of each one ?). This is called statistical fallacy, which may deviate you from the real situation. So, it is very important to collect the data to know the facts and figures, but equally important is the presentation of data. Today, the use of statistical methods in the analysis, presentation and in drawing conclusions plays a significant role in almost all disciplines, including geography, which use the data. It may, therefore, be inferred that the concentration of a phenomena, e.g. population, forest or network of transportation or communication not only vary over space and time but may also be conveniently explained using the data. In other words, you may say that there is a shift from qualitative description to quantitative analysis in explaining the relationship among variables. Hence, analytical tools and techniques have become more important these days to make the study more logical and derive precise conclusion. Precise quantitative techniques are used right from the beginning of collecting and compiling data to its tabulation, organisation, ordering and analysis till the derivation of conclusions.

Sources of Data The data are collected through the following ways. These are : 1. Primary Sources, and 2. Secondary Sources. The data which are collected for the first time by an individual or the group of individuals, institution/organisations are called Primary sources of the data. On the other hand, data collected from any published or unpublished sources are called Secondary sources. Fig. 1.1 shows the different methods of data collection.

Sources of Primary Data 1. Personal Observations It refers to the collection of information by an individual or group of individuals through direct observations in the field. Through a field survey, information about the relief features, drainage patterns, types of soil and natural vegetation, as well as population structure, sex ratio, literacy, means of transport and communication, urban and rural settlements, etc. is collected. However, in carrying

METHODS OF DATA COLLECTION

Secondary Data

Primary Data

Personal Observation

Interview

Published Resources

Government

Quasigovernment

Government

Questionnaire/ Schedule

Unpublished Resources

International

Quasigovernment

Other Methods

Private Publications

Private Documents

Newspaper

Other Documents

Fig. 1.1 : Methods of Data Collection

3 Data–Its Source and Compilation

out personal observations, the person(s) involved must have theoretical knowledge of the subject and scientific attitude for unbiased evaluation. 2. Interview In this method, the researcher gets direct information from the respondent through dialogues and conversations. However, the interviewer must take the following precautions while conducting an interview with people of the area: (i) A precise list of items about which information is to be gathered from the persons interviewed be prepared. (ii) The person(s) involved in conducting the interview should be clear about the objective of the survey. (iii) The respondents should be taken into confidence before asking any sensitive question and he/she be assured that the secrecy will be maintained. (iv) A congenial atmosphere should be created so that the respondent may explain the facts without any hesitation. (v) The language of the questions should be simple and polite so that the respondents feel motivated and readily agree to give information asked for. (vi) Avoid asking any such question that may hurt the self – respect or the religious feelings of the respondent. (vii) At the end of interview, ask the respondent what additional information he/she may provide, other than what has already been provided by him/her. (viii) Pay your thanks and gratefulness for sparing his/her valuable time for you.

3. Questionnaire/Schedule In this method, simple questions and their possible answers are written on a plain paper and the respondents have to tick-mark the possible answers from the given choices. At times, a set of structured questions are written and sufficient space is provided in the questionnaire where the respondent write their opinion. The objectives of the survey should be clearly mentioned in the questionnaire. This method is useful in carrying out the survey of a larger area. Even questionnaire can be mailed to far-flung places. The limitation of the method is that only the literate and educated people can be approached to provide the required information. Similar to the questionnaire that contains the questions pertaining to the matter of investigation is the schedule. The only difference between the questionnaire and the schedule is that the respondent himself/ herself fills up the questionnaires, whereas a properly trained enumerator himself fills up schedules by asking question addressed to the respondents. The main advantage of schedule over the questionnaire is that the information from both literate and illiterate respondents can be collected. 4. Other Methods The data about the properties of soil and water are collected directly in the field by measuring their characteristics using soil kit and water quality kit. Similarly, field scientist collect data about the health of the crops and vegetation using transducers (Fig. 1.2).

Secondary Source of Data

P ractical W ork in Geography, P art-II Work Part-II

4

Secondary sources of data consist of published and unpublished records which include government publications, documents and reports. Published Sources

Fig. 1.2 : Field Scientist taking Measures of Crop Health

1. Government Publications The publications of the various ministries and the departments of the Government of India, state governments and the District Bulletins are one of the most important sources of secondary information. These include the Census of India published by the Office of the Registrar General of India, reports of the National Sample Survey, Weather Reports of Indian Meteorological Department, and Statistical Abstracts published by state governments, and the periodical reports published by different Commissions. Some of the government publications are shown in Fig. 1.3.

Fig. 1.3 : Some of the Government Publications

2. Semi/Quasi-government Publications The publications and reports of Urban Development Authorities and Municipal Corporations of various cities and towns, Zila Parishads (District Councils), etc. fall under this category. 3. International Publications The international publications comprise yearbooks, reports and monographs published by different agencies of the United Nations such as United Nations Educational, Scientific and Cultural Organisation (UNESCO), United Nations Development Programme (UNDP), World Health Organisation (WHO), Food and Agricultural Organisation (FAO), etc. Some of the important publications of the United Nations that are periodically published are Demographic Year Book, Statistical Year Book and the Human Development Report (Fig. 1.4). 4. Private Publications

Fig. 1.4 : Some of the United Nations Publications

The yearbooks, surveys, research reports and monographs published by newspapers and private organisations fall under this category. 5. Newspapers and Magazines

6. Electronic Media The electronic media specially internet has emerged as a major source of secondary data in recent times. Unpublished Sources 1. Government Documents The unpublished reports, monographs and documents are yet another source of secondary data. These documents are prepared and maintained as unpublished record at different levels of governance. For example, the village level revenue records maintained by the patwaris of respective villages serve as an important source of village level information. 2. Quasi-government Records The periodical reports and the development plans prepared and maintained by different Municipal Corporations, District Councils, and Civil Services departments are included in Quasi – government records.

Data–Its Source and Compilation

The daily newspapers and the weekly, fortnightly and monthly magazines serve as easily accessible source of secondary data.

5

3. Private Documents These include unpublished reports and records of companies, trade unions, different political and apolitical organisations and resident welfare associations.

Tabulation and Classification of Data The data collected from primary or secondary sources initially appear as a big jumble of information with the least of comprehension. This is known as raw data. To draw meaningful inferences and to make them usable the raw data requires tabulation and classification. One of the simplest devices to summarise and present the data is the Statistical Table. It is a systematic arrangement of data in columns and rows. The purpose of table is to simplify the presentation and to facilitate comparisons. This table enables the reader to locate the desired information quickly. Thus, the tables make it possible for the analyst to present a huge mass of data in an orderly manner within a minimum of space.

Data Compilation and Presentation Data are collected, tabulated and presented in a tabular form either in absolute terms, percentages or indices. Absolute Data When data are presented in their original form as integers, they are called absolute data or raw data. For example, the total population of a country or a state, the total production of a crop or a manufacturing industry, etc. Table 1.1 shows the absolute data of population of India and some of the selected states.

6

State/ UT Code

P ractical W ork in Geography, P art-II Work Part-II

Table 1.1 : Population of India and Selected States/Union Territories, 2001

1 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

India/State/ Union territory

Total Population

2 INDIA * Jammu & Kashmir Himachal Pradesh Punjab Chandigarh ## Uttaranchal Haryana National Capital Territory of Delhi Rajasthan Uttar Pradesh Bihar

#

Persons

Males

Females

3

4

5

1,027,015,247 10,069,917 6,077,248 24,289,296 900,914 8,479,562 21,082,989 13,782,976

531,277,078 5,300,574 3,085,256 12,963,362 508,224 4,316,401 11,327,658 7,570,890

495,738,169 4,769,343 2,991,992 11,325,934 392,690 4,163,161 9,755,331 6,212,086

56,473,122 166,052,859 82,878,796

29,381,657 87,466,301 43,153,964

27,091,465 78,586,558 39,724,832

* inclusive of all territorial boundary of India # excluding PoK ## Union Territory

Percentage/Ratio Some time data are tabulated in a ratio or percentage form that are computed from a common parameter, such as literacy rate or growth rate of population, percentage of agricultural products or industrial products, etc. Table 1.2 presents

literacy rates of India over the decades in a percentage form. Literacy Rate is calculated as : Total Literates Total Population × 100 Index Number

Table 1.2 : Literacy Rate* : 1951 – 2001 Year

Person

Male

Female

1951

18.33

27.16

8.86

1961

28.3

40.4

15.35

1971

34.45

45.96

21.97

1981

43.57

56.38

29.76

1991

52.21

64.13

39.29

An index number is a statistical 2001 64.84 75.85 54.16 measure designed to show changes in variable or a group of related variables * as percentage of total Source: Census of India, 2001 with respect to time, geographic location or other characteristics. It is to be noted that index numbers not only measure changes over a period of time but also compare economic conditions of different locations, industries, cities or countries. Index number is widely used in economics and business to see changes in price and quantity. There are various methods for the calculation of index number. However, the simple aggregate method is most commonly used. It is obtained using the following formula:

∑q ∑q

1

× 100

0

∑q ∑q

1

= Total of the current year production

0

= Total of the base year production

Generally base year values are taken as 100 and index number is calculated thereupon. For example, Table 1.3 shows the production of iron ore in India and the changes in index number from 1970 – 71 to 2000 – 01 taking 1970-71 as the base year. Production (in million tonnes) 1970-71

32.5

1980-81

42.2

1990-91

53.7

2000-01

67.4

Calculation

32.5 32.5 42.2 32.5 53.7 32.5 67.4 32.5

Index Number

× 100

100

× 100

130

× 100

165

× 100

207

Source – India : Economic Year Book, 2005

Processing of Data The processing of raw data requires their tabulation and classification in selected classes. For example, the data given in Table 1.4 can be used to understand how they are processed. We can see that the given data are ungrouped. Hence, the first step is to group data in order to reduce its volume and make it easy to understand.

Data–Its Source and Compilation

Table 1.3 : Production of Iron ore in India

7

Table 1.4 : Score of 60 Students in Geography Paper 47 89 32 18 56 64

02 96 22 51 58 37

39 74 53 36 43 17

64 06 62 58 74 31

22 26 73 28 64 41

46 15 57 65 12 71

28 92 37 63 35 56

02 84 44 59 42 83

09 84 67 75 68 59

10 90 50 70 80 90

Grouping of Data The grouping of the raw data requires determining of the number of classes in which the raw data are to be grouped and what will be the class intervals. The selection of the class interval and the number of classes, however, depends upon the range of raw data. The raw data given in Table 1.4 ranges from 02 to 96. We can, therefore, conveniently choose to group the data into ten classes with an interval of ten units in each group, e.g. 0 – 10, 10 – 20, 20 – 30, etc. (Table 1.5). Table 1.5 : Making Tally Marks to Obtain Frequency Group

Tally Marks

Number of Individual

0-10

02,02,09,06

4

10-20

10,15,18,12,17

5

20-30

22,28,26,22,28

5

30-40

39,32,37,36,35,37,31

7

40-50

47,46,44,43,42,41

6

50-60

53,57,50,51,58,

10

8

59,56,58,56,59 60-70

P ractical W ork in Geography, P art-II Work Part-II

Numerical of Raw Data

64,62,67,65,

8

63,64,68,64 70-80

74,73,75,70,74,71

6

80-90

89,84,84,80,83

5

90-100

96,92,90,90

4

∑f

= N = 60

Process of Classification Once the number of groups and the class interval of each group are determined, the raw data are classified as shown in Table 1.5. It is done by a method popularly known as Four and Cross Method or tally marks. First of all, one tally mark is assigned to each individual in the group in which it is falling. For example, the first numerical in the raw data is 47. Since, it falls in the group of 40 – 50, one tally mark is recorded in the column 3 of Table 1.5. Frequency Distribution In Table 1.5 we have classified the raw data of a quantitative variable and have grouped them class-wise. The numbers of individuals (places in the fourth column of Table 1.5) are known as frequency and the column represents the frequency

distribution. It illustrates how the different values of a variable are distributed in different classes. Frequencies are classified as Simple and Cumulative frequencies. Simple Frequencies It is expressed by ‘f’ and represent the number of individuals falling in each group (Table 1.6). The sum of all the frequencies, assigned to all classes, represents the total number of individual observations in the given series. In statistics, it is expressed by the symbol N that is equal to ∑ f . It is expressed as

∑f

= N = 60 (Table 1.5 and 1.6).

Table 1.6 : Frequency Distribution Group

f

Cf

00-10

4

4

10-20

5

9

20-30

5

14

30-40

7

21

40-50

6

27

50-60

10

37

60-70

8

45

70-80

6

51

80-90

5

56

90-100

4

60

∑f

= N = 60

Cumulative Frequencies It is expressed by ‘Cf’ and can be obtained by adding successive simple frequencies in each group with the previous sum, as shown in the column 3 of Table 1.6. For example, the first simple frequency in Table 1.6 is 4. Next frequency of 5 is added to 4 which gives a total of 9 as the next cumulative frequency. Likewise add every next number until the last cumulative frequency of 60 is obtained. Note that it is equal to N or ∑ f .

Exclusive Method As shown in Table 1.6, two numbers are shown in its first column . Notice that the upper limit of one group is the same as the lower limit of the next group. For example, the upper limit of the one group (20 – 30) is 30, which is the lower limit of the next group (30 – 40), making 30 to appear in both groups. But any observation having the value of 30 is included in the group where it is at its lower limit and it is excluded from the group where it is the upper limit as (in 20-30 groups). That is why the method is known as exclusive method, i.e. a group is excluded of its upper limits. You may now make out where all the marginal values of Table 1.4 will go. The groups in Table 1.6, are interpreted in the following manner – 0 and under 10 10 and under 20 20 and under 30 30 and under 40 40 and under 50 50 and under 60 60 and under 70 70 and under 80 80 and under 90 90 and under100 Hence, in this type of grouping the class extends over ten units. For example, 20, 21, 22, 23, 24, 25, 26, 27, 28 and 29 are included in the third group.

9 Data–Its Source and Compilation

Advantage of cumulative frequency is that one can easily make out that there are 27 individuals scoring less than 50 or that 45 out of 60 individuals lie below the score of 70. Each simple frequency is associated with its group or class. The exclusive or inclusive methods are used for forming the groups or classes.

Inclusive Method

Table 1.7 : Frequency Distribution

In this method, a value equal to the Group f upper limit of a group is included in 0–9 4 the same group. Therefore, it is known 10 – 19 5 as inclusive method. Classes are 20 – 29 5 mentioned in a different form in this method, as is shown in the first 30 – 39 7 column of Table 1.7. Normally, the 40 – 49 6 upper limit of a group differs by 1 with 50 – 59 10 the lower limits of the next group. It 60 – 69 8 is important to note that each group 70 – 79 6 spreads over ten units in this method 80 – 89 5 also. For example, the group of 50 – 90 – 99 4 59 includes the ten values i.e. 50, 51, ∑ f = N = 60 52, 53, 54, 55, 56, 57, 58 and 59 (Table 1.7). In this method both upper and lower limit are included to find the frequency distribution.

Cf 4 9 14 21 27 37 45 51 56 60

Frequency Polygon

P ractical W ork in Geography, P art-II Work Part-II

10

A graph of frequency distribution is known as the frequency polygon. It helps in comparing the two or more than two frequency distributions (Fig.1.5). The two frequencies are shown using a bar diagram and a line graph respectively. Ogive When the frequencies are added they are called cumulative Fig. 1.5 : Frequency Distribution Polygon frequencies and are listed in a table called cumulative frequency table. The curve obtained by plotting cumulative frequencies is called an Ogive (pronounced as ojive). It is constructed either by the less than method or the more than method. In the less than method, we start with the upper limit of the classes and go on adding the frequencies. When these frequencies are plotted, we get a rising curve as shown in Table 1.8 and Fig. 1.6. In the more than method, we start with the lower limits of the classes and from the cumulative frequency, we substract frequency of each class. When these frequencies are plotted, we get a declining curve as shown in Table 1.9 and Fig 1.7. Both the Figs. 1.5 and 1.6 may be combined to get a comparative picture of less than and more than Ogive as shown in Table 1.10 and Fig. 1.7.

Table 1.8 : Frequency Distribution less than Method Less than Method Less Less Less Less Less Less Less Less Less Less

than than than than than than than than than than

Cf

10 20 30 40 50 60 70 80 90 100

4 9 14 21 27 37 45 51 56 60

Fig. 1.6 : Less than Ogive

Table 1.9 : Frequency Distribution more than Method More than Method than than than than than than than than than than

0 10 20 30 40 50 60 70 80 90

60 56 51 44 38 28 20 14 9 4

11

Fig. 1.7 : More than Ogive

Table 1.10 : Less than and more than Ogive Marks Less obtained than

More than

0 - 10

4

60

10 - 20

9

56

20 - 30

14

51

30 - 40

21

44

30 - 40

27

38

50 - 60

37

28

60 - 70

45

20

70 - 80

51

14

80 - 90

56

9

90 - 100

60

4

Fig. 1.8 : Less than and more than Ogive

Data–Its Source and Compilation

More More More More More More More More More More

Cf

Excercises 1. Choose the right answer from the four alternatives given below: (i) A number or character which represents measurement is called (a) Digit (b) Data (c) Number (d) Character (ii) A single datum is a single measurement from the (a) Table (b) Frequency (c) Real world

(d) Information

(iii) In a tally mark grouping by four and crossing fifth is called (a) Four and Cross Method (b) Tally Marking Method (c) Frequency plotting Method (d) Inclusive Method (iv) An (a) (b) (c) (d)

Ogive is a method in which Simple frequency is measured Cumulative frequency is measured Simple frequency is plotted Cumulative frequency is plotted

(v) If both ends of a group are taken in frequency grouping, it is called (a) Exclusive Method (b) Inclusive Method (c) Marking Method (d) Statistical Method 2. Answer the following questions in about 30 words: (i) Differentiate between data and information. (ii) What do you mean by data processing? (iii) What is the advantage of foot note in a table? (iv) What do you mean by primary sources of data? (v) Enumerate five sources of secondary data. 3. Answer the following questions in about 125 words:

P ractical W ork in Geography, P art-II Work Part-II

12

(i) Discuss the national and international agencies where from secondary data may be collected. (ii) What is the importance of an index number? Taking an example examine the process of calculating an index number and show the changes.

Activity 1. In a class of 35 students of Geography, following marks were obtained out of 10 marks in unit test – 1, 0, 2, 3, 4, 5, 6, 7, 2, 3, 4, 0, 2, 5, 8, 4, 5, 3, 6, 3, 2, 7, 6, 5, 4, 3, 7, 8, 9, 7, 9, 4, 5, 4, 3. Represent the data in the form of a group frequency distribution. 2. Collect the last test result of Geography of your class and represent the marks in the form of a group frequency distribution.

You have learnt in previous chapter that organising and presenting data makes them comprehensible. It facilitates data processing. A number of statistical techniques are used to analyse the data. In this chapter, you will learn the following statistical techniques: 1. Measures of Central Tendency 2. Measures of Dispersion 3. Measures of Relationship While measures of central tendency provide the value that is an ideal representative of a set of observations, the measures of dispersion take into account the internal variations of the data, often around a measure of central tendency. The measures of relationship, on the other hand, provide the degree of association between any two or more related phenomena, like rainfall and incidence of flood or fertiliser consumption and yield of crops.

Measures of Central Tendency The measurable characteristics such as rainfall, elevation, density of population, levels of educational attainment or age groups vary. If we want to understand them, how would we do ? We may, perhaps, require a single value or number that best represents all the observations. This single value usually lies near the centre of a distribution rather than at either extreme. The statistical techniques used to find out the centre of distributions are referred as measures of central tendency. The number denoting the central tendency is the representative figure for the entire data set because it is the point about which items have a tendency to cluster. Measures of central tendency are also known as statistical averages. There are a number of the measures of central tendency, such as the mean, median and the mode. Mean The mean is the value which is derived by summing all the values and dividing it by the number of observations.

Median The median is the value of the rank, which divides the arranged series into two equal numbers. It is independent of the actual value. Arranging the data in ascending or descending order and then finding the value of the middle ranking number is the most significant in calculating the median. In case of the even numbers the average of the two middle ranking values will be the median. Mode Mode is the maximum occurrence or frequency at a particular point or value. You may notice that each one of these measures is a different method of determining a single representative number suited to different types of the data sets. Mean Mean is the simple arithmetic average of the different values of a variable. For ungrouped and grouped data, the methods for calculating mean are necessarily different. Mean can be calculated by direct or indirect methods, for both grouped and ungrouped data. Computing Mean from Ungrouped Data Direct Method While calculating mean from ungrouped data using the direct method, the values for each observation are added and the total number of occurrences are divided by the sum of all observations. The mean is calculated using the following formula: 14 Practical W ork in Geography, P art-II Work Part-II

X

x N

Where, Table 2.1 : Calculation of Mean Rainfall

X = Mean = Sum of a series of measures x = A raw score in a series of measures x = The sum of all the measures N = Number of measures Example 2.1 : Calculate the mean rainfall for Malwa Plateau in Madhya Pradesh from the rainfall of the districts of the region given in Table 2.1:

Districts in Normal Rainfall Malwa Plateau in mms Indirect Method x Direct Method Indore Dewas Dhar Ratlam Ujjain Mandsaur Shajapur

N

x and

d

x

d

and

N

d= x-800*

979 1083 833 896 891 825 977

179 283 33 96 91 25 177

6484

884

926.29

126.29

* Where 800 is assumed mean. d is deviation from the assumed mean.

The mean for the data given in Table 2.1 is computed as under : x

X

N 6, 484 7

926.29

It could be noted from the computation of the mean that the raw rainfall data have been added directly and the sum is divided by the number of observations i. e. districts. Therefore, it is known as direct method. Indirect Method For large number of observations, the indirect method is normally used to compute the mean. It helps in reducing the values of the observations to smaller numbers by subtracting a constant value from them. For example, as shown in Table 2.1, the rainfall values lie between 800 and 1100 mm. We can reduce these values by selecting ‘assumed mean’ and subtracting the chosen number from each value. In the present case, we have taken 800 as assumed mean. Such an operation is known as coding. The mean is then worked out from these reduced numbers (Column 3 of Table 2.1). The following formula is used in computing the mean using indirect method: X

Where, A

d

A

=

d =

N

Subtracted constant Sum of the coded scores

X

884 7

800

= 800+

884 7

X 926.29 mm Note that the mean value comes the same when computed either of the two methods.

Computing Mean from Grouped Data The mean is also computed for the grouped data using either direct or indirect method. Direct Method When scores are grouped into a frequency distribution, the individual values lose their identity. These values are represented by the midpoints of the class intervals in which they are located. While computing the mean from grouped

Processing Data P rocessing

N = Number of individual observations in a series Mean for the data as shown in Table 2.1 can be computed using the indirect method in the following manner :

15

data using direct method, the midpoint of each class interval is multiplied with its corresponding frequency ( f ); all values of fx (the X are the midpoints) are fx that is finally divided by the number of observations i. e.

added to obtain

N. Hence, mean is calculated using the following formula : X

fx N

Where :

X = f x

= =

Mean Frequencies Midpoints of class intervals

N

=

Number of observations (it may also be defined as

f )

Example 2.2 : Compute the average wage rate of factory workers using data given in Table 2.2: Table 2.2 : Wage Rate of Factory Workers Wage Rate (Rs./day)

Number of workers (f)

Classes

f

50 70 90 110 130

Practical W ork in Geography, P art-II Work Part-II

16

-

70 90 110 130 150

10 20 25 35 9

Table 2.3 : Computation of Mean Classes

Frequency (f)

Midpoints (x)

fx

d=x-100

fd

U = (x-100)/ 20

fu

50-70 70-90 90-110 110-130 130-150

10 20 25 35 9

60 80 100 120 140

600 1,600 2,500 4,200 1,260

-40 -20 0 20 40

-400 -400 0 700 360

-2 -1 0 1 2

-20 -20 0 35 18

fx

and

f =99

10,160

fx

Where N =

fx =

fd =

260

fu =

13

f = 99

Table 2.3 provides the procedure for calculating the mean for grouped data. In the given frequency distribution, ninety-nine workers have been grouped into five classes of wage rates. The midpoints of these groups are listed in the third column. To find the mean, each midpoint (X) has been multiplied by the frequency fx ) divided by N. ( f ) and their sum (

The mean may be computed as under using the given formula : fx

X

N

10,160 99

= 102.6 Indirect Method The following formula can be used for the indirect method for grouped data. The principles of this formula are similar to that of the indirect method given for ungrouped data. It is expressed as under x

A

fd N

Where, A =

f = d =

Midpoint of the assumed mean group (The assumed mean group in Table 2.3 is 90 – 110 with 100 as midpoint.) Frequency Deviation from the assumed mean group (A)

N =

Sum of cases or

f

x

A

fd N

260 99 = 100 + 2.6

= 100 +

= 102.6 Note : The Indirect mean method will work for both equal and unequal class intervals.

17 Processing Data P rocessing

i = Interval width (in this case, it is 20) From Table 2.3 the following steps involved in computing mean using the direct method can be deduced : (i) Mean has been assumed in the group of 90 – 110. It is preferably assumed from the class as near to the middle of the series as possible. This procedure minimises the magnitude of computation. In Table 2.3, A (assumed mean) is 100, the midpoint of the class 90 – 110. (ii) The fifth column (u) lists the deviations of midpoint of each class from the midpoint of the assumed mean group (90 – 110). (iii) The sixth column shows the multiplied values of each f by its corresponding d to give fd. Then, positive and negative values of fd are f d ). Note added separately and their absolute difference is found ( f d is replaced in the formula following A, that the sign attached to where ± is given. The mean using indirect method is computed as under :

Median Median is a positional average. It may be defined “as the point in a distribution with an equal number of cases on each side of it”. The Median is expressed using symbol M. Computing Median for Ungrouped Data When the scores are ungrouped, these are arranged in ascending or descending order. Median can be found by locating the central observation or value in the arranged series. The central value may be located from either end of the series arranged in ascending or descending order. The following equation is used to compute the median : N

Value of

1 2

th item

Example 2.3: Calculate median height of mountain peaks in parts of the Himalayas using the following: 8,126 m, 8,611m, 7,817 m, 8,172 m, 8,076 m, 8,848 m, 8,598 m. Computation : Median (M) may be calculated in the following steps : (i) Arrange the given data in ascending or descending order. (ii) Apply the formula for locating the central value in the series. Thus : Value of ( =

Practical W ork in Geography, P art-II Work Part-II

18

7

1 2

N

1 2

) th item

th item

8 th item 2

4th item in the arranged series will be the Median. Arrangement of data in ascending order – 7,817; 8,076; 8,126; 8,172; 8,598; 8,611; 8,848

4th item Hence, M = 8,172 m Computing Median for Grouped Data When the scores are grouped, we have to find the value of the point where an individual or observation is centrally located in the group. It can be computed using the following formula : M

l

i f

N 2

c

Where, M l i f N c

= = = = = =

Median for grouped data Lower limit of the median class Interval Frequency of the median class Total number of frequencies or number of observations Cumulative frequency of the pre-median class.

Example 2.4 : Calculate the median for the following distribution : class

50-60

60-70

70-80

80-90

90-100

100-110

f

3

7

11

16

8

5

Table 2.4 : Computation of Median Class

Frequency (f)

50-60 60-70 70-80 80-90 (median group) 90-100 100-110

Cumulative Frequency (F)

3 7 11 16 f

3 10 21c 37

8 5

45 50

f or

Calculation of Median Class

M= =

N 2

50 2

= 25

N= 50

19

(iii)

Median number is obtained by

N 50 i.e. = 25 in this case, as shown in 2 2

column 4 of Table 2.4. (iv)

(v)

Count into the cumulative frequency distribution (F) from the top N is reached. In this towards bottom until the value next greater than 2 N is 25, which falls in the Class interval of 40-44 with example, 2 cumulative frequency of 37, thus the cumulative frequency of the premedian class is 21 and actual frequency of the median class is 16. The median is then computed by substituting all the values determined in the step 4 in the following equation : M

l

i (m f

c)

Processing Data P rocessing

The median is computed in the steps given below : (i) The frequency table is set up as in Table 2.4. (ii) Cumulative frequencies (F) are obtained by adding each normal frequency of the successive interval groups, as given in column 3 of Table 2.4.

10 (25 - 21) 16

80 80 80

M

5 8

4 5 2

80 2.5 82.5

Mode The value that occurs most frequently in a distribution is referred to as mode. It is symbolised as Z or M0. Mode is a measure that is less widely used compared to mean and median. There can be more than one type mode in a given data set. Computing Mode for Ungrouped Data While computing mode from the given data sets all measures are first arranged in ascending or descending order. It helps in identifying the most frequently occurring measure easily.

Practical W ork in Geography, P art-II Work Part-II

20

Example 2.5 : Calculate mode for the following test scores in geography for ten students : 61, 10, 88, 37, 61, 72, 55, 61, 46, 22 Computation : To find the mode the measures are arranged in ascending order as given below: 10, 22, 37, 46, 55, 61, 61, 61, 72, 88. The measure 61 occurring three times in the series is the mode in the given dataset. As no other number is in the similar way in the dataset, it possesses the property of being unimodal. Example 2.6 : Calculate the mode using a different sample of ten other students, who scored: 82, 11, 57, 82, 08, 11, 82, 95, 41, 11. Computation : Arrange the given measures in an ascending order as shown below : 08, 11, 11, 11, 41, 57, 82, 82, 82, 95 It can easily be observed that measures of 11 and 82 both are occurring three times in the distribution. The dataset, therefore, is bimodal in appearance. If three values have equal and highest frequency, the series is trimodal. Similarly, a recurrence of many measures in a series makes it multimodal. However, when there is no measure being repeated in a series it is designated as without mode.

Comparison of Mean, Median and Mode The three measures of the central tendency could easily be compared with the help of normal distribution curve. The normal curve refers to a frequency distribution in which the graph of scores often called a bell-shaped curve. Many

human traits such as intelligence, personality scores and student achievements have normal distributions. The bell-shaped curve looks the way it does, as it is symmetrical. In other words, most of the observations lie on and around the middle value. As one approaches the extreme values, the number of observations reduces in a symmetrical manner. A normal curve can have high or low data variability. An example of a normal distribution curve is given in Fig. 2.3.

Fig. 2.3 : Normal Distribution Curve

Fig. 2.4 : Positive Skew

21 Processing Data P rocessing

The normal distribution has an important characteristic. The mean, median and mode are the same score (a score of 100 in Fig. 2.3) because a normal distribution is symmetrical. The score with the highest frequency occurs in the middle of the distribution and exactly half of the scores occur above the middle and half of the scores occur below. Most of the scores occur around the middle of the distribution or the mean. Very high and very low scores do not occur frequently and are, therefore, considered rare. If the data are skewed or distorted in some way, the mean, median and mode will not coincide and the effect of the skewed data needs to be considered (Fig. 2.4 and 2.5).

Fig. 2.5 : Negative Skew

Measures of Dispersion The measures of Central tendency alone do not adequately describe a distribution as they simply locate the centre of a distribution and do not tell us anything about how the scores or measurements are scattered in relation to the centre. Let us use the data given in Table 2.5 and 2.6 to understand the limitations of the measures of central tendency.

Practical W ork in Geography, P art-II Work Part-II

22

Table 2.5 : Scores of Individuals

Table 2.6 : Scores of Individuals

Individual

Individual

X1 X2 X3 X4 X5

Score 52 55 50 48 45

Score

X1 X2 X3 X4 X5

28 00 98 55 69

X = 50 for both the distributions It can be observed that the mean derived from the two data sets (Table 2.5 and 2.6) is same i. e. 50. The highest and the lowest score shown in Table 2.5 is 55 and 45 respectively. The distribution in Table 2.6 has a high score of 98 and a low score of zero. The range of the first distribution is 10, whereas, it is 98 in the second distribution. Although, the mean for both the groups is the same, the first group is obviously stable or homogeneous as compared to the distribution of score of the second group, which is highly unstable or heterogeneous. This raises a question whether the mean is a sufficient indicator of the total character of distributions. The examples provide profound evidence that it is not so. Thus, to get a better picture of a distribution, we need to use a measure of central tendency and of dispersion or variability. The term dispersion refers to the scattering of scores about the measure of central tendency. It is used to measure the extent to which individual items or numerical data tend to vary or spread about an average value. Thus, the

dispersion is the degree of spread or scatter or variation of measures about a central value. The dispersion serves the following two basic purposes : (i) It gives us the nature of composition of a series or distribution, and (ii) It permits comparison of the given distributions in terms of stability or homogeneity.

Methods of Measuring Dispersion The following methods are used as measures of dispersion : 1. Range 2. Quartile Deviation 3. Mean Deviation 4. Standard Deviation and Co-efficient of Variation (C.V.) 5. Lorenz Curve Each of these methods has definite advantages as well as limitations. Hence, there is a need to use either of the methods with great precautions. The Standard Deviation (s) as an absolute measure of dispersion and Co-efficient of Variation (cv) as a relative measure of dispersion, besides the Range are most commonly used measures of dispersion. We will discuss how each one of these measures is computed. Range Range (R) is the difference between maximum and minimum values in a series of distribution. This way it simply represents the distance from the smallest to the largest score in a series. It can also be defined as the highest score minus the lowest score.

Example 2.7 : Calculate the range for the following distribution of daily wages: Rs. 40, 42, 45, 48, 50, 52, 55, 58, 60, 100. Computation of Range The R can be calculated with the help of the following formula : R L S Where ‘R’ is Range, ‘L’ and ‘S’ is the largest and smallest values respectively in a series. Hence, R = L–S = 100 – 40 = 60 If we eliminate the 10th case, R becomes 20 (60 – 40). The elimination of one score has reduced the R to just one-third. It is obvious that the difficulty with R as a measure of variability is that its value is wholly dependent upon the two extreme scores. Thus, as a measure of dispersion R functions much the same way as mode does as a measure of central tendency. Both the measures are highly unstable.

Processing Data P rocessing

Range for Ungrouped Data

23

Standard Deviation Standard deviation (SD) is the most widely used measure of dispersion. It is defined as the square root of the average of squares of deviations. It is always calculated around the mean. The standard deviation is the most stable measure of variability and is used in so many other statistical operations. The Greek character denotes it. To obtain SD, deviation of each score from the mean (x) is first squared (x2). It is important to note that this step makes all negative signs of deviations positive. It saves SD from the major criticism of mean deviation which uses modulus x. Then, all of the squared deviations are summed - x2 (care should be taken that these are not summed first and then squared). This sum of the squared deviations ( x2) is divided by the number of cases and then the square root is taken. Therefore, Standard Deviation is defined as the root mean square deviation. For a given data set, it is computed using the following formula : x2 N During these steps, we come across a term before taking its square root. It is assigned a special name, the variance. The variance is widely used in advanced statistical operations. Its square root is standard deviation. That way, the opposite is also true i.e. square of SD is variance.

Standard Deviation for Ungrouped Data Example 2.8 : Calculate the standard deviation for the following scores :

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01, 03, 05, 07, 09

Table 2.7 : Computation of Standard Deviation X

x2 N

40 5

1 3 5 7 9 X

8

2.83

2.828

x(X

X)

–4 –2/–6 0 2 6-Apr

x2 16 4 0 4 16

25

N =5

∴=5

Let us summarise the steps used in the above computation : (i) All the scores have been placed in the column marked X. (ii) Summing the raw scores and dividing by N have found mean. (iii) Deviation of each raw score (x) has been obtained by subtracting the mean from them. A check on our work is that the sum of the x should be zero. We find that this is true for our exercise. (iv) Each value of x has been squared and summed. (v) Sum of the x2s has been divided by N. Recall that the resultant is the variance. (vi) Its square root has been found to obtain Standard Deviation.

Computation of Standard Deviation for Grouped Data Example : Calculate the standard deviation for the following distribution: Groups

120-130 130-140 140-150 150-160

f

2

4

6

160-170 170-180

12

10

6

The method of obtaining SD for grouped data has been explained in the table below. The initial steps upto column 4, are the same as those we followed in the computation of the mean for grouped data. We begin with assuming our mean to exist in the interval group of 150-160, hence a deviation value of zero has been assigned to the group. Likewise other deviations are determined. Values in column 4 (fx´) are obtained by the multiplication of the values in the two previous columns. Values in column 5 (fx´2) are obtained by multiplying the values given in column 3 and 4. Then various columns have been summed. (1)

(2)

(3)

(4)

(5)

Group

f

x´

fx´

fx´2

120 - 130

2

–3

–6

18

130 - 140

4

–2

–8

16

140 - 150

6

–1

150 - 160

12

0

0

0

160 - 170

10

1

10

10

170 - 180

6

2

6 20

6

12 22

24

2

fx ´2 =74

The following formula is used to calculate the Standard Deviation : SD

i 2|

fx'2

fx ' N

Coefficient of Variation (CV) When the observations for different places or periods are expressed in different units of measurement and are to be compared, the coefficient of variation (CV) proves very useful. CV expresses the standard deviation as a percentage of the mean. It is determined using the following formula :

CV

Standard Deviation 100 Mean

Processing Data P rocessing

fx ´

N=40

25

CV

X

100

The CV for the dataset given in Table 2.7 will, hence, be as under :

CV CV

X

100

2.83 100 5

CV = 56% Coefficient of Variation for grouped data can also be calculated using the same formula.

Rank Correlation

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The statistical methods discussed so far were concerned with the analysis of a single variable. We will now discuss the methods of exploring relationship between two variables and the way this relationship is expressed numerically. When dealing with two or more sets of data, curiosity arises for knowing whether or not changes in one variable produce changes in some other variable. Often our interest lies in knowing the nature of relationship or interdependence between two or more sets of data. It has been found that the correlation serves useful purpose. It is basically a measure of relationship between two or more sets of data. Since, we study the way they vary, we call these events variables. Thus, the term correlation refers to the nature and strength of correspondence or relationship between two variables. The terms nature and strength in the definition refer to the direction and degree of the variables with which they co-vary.

Direction of Correlation It is our common experience that an input is made to get some output. There could be three possibilities. 1. With the increase in input the output also increases. 2. With the increase in the input the output decreases. 3. Change in the input does not lead to change in the output. In the first case, the direction of the relationship between the input and output is in the same direction. It is called that both are positively correlated. In the second case the direction of change between the input and output is in the opposite direction and it is called that they are negatively correlated. In the third case, change in the input has no relationship with the output, hence, it is said that these do not have a statistically significant relationship. Let us now consider Fig. 2.7 which looks just opposite of Fig. 2.6. The plotted values run from the upper left to the lower right of the graph. Notice that for every increase of one unit on the X-axis, there is a corresponding decrease of two units on the Y-axis. It is an example of a negative correlation. It means that the two variables have a tendency to move opposite to each other, i.e. if one variable increases, the other decreases and vice versa. We can find such relationships existing between various geographical pairs of variables. Correlations between

height above sea level and air pressure, temperature and air pressure are few examples. It implies that the obtained figure of correlation must precede with the arithmetical sign (plus or minus), more importantly in the negative correlation.

Fig. 2.6 : Perfect Positive Correlation

Fig. 2.7 : Perfect Negative Correlation

Degree of Correlation

Fig. 2.8 : Spread of Direction and Degree of Correlation

Perfect Correlations Figs. 2.6 and 2.7 have been constructed to show the typical relationship between two variables. Notice that these graphs show the scattering of X – Y values. Therefore, such graphs are referred to as scatter gram or scatter plot. It may be noted from Fig. 2.6, that the pairs of values like these, when plotted, fall along a straight line and when this straight line runs from the lower left of the scatter plot to the upper right, it is an example of a perfect positive correlation (1.00).

27 Processing Data P rocessing

When reference has been made about the direction of correlation, negative or positive, a natural curiosity arises to know the degree of correspondence or association of the two variables. The maximum degree of correspondence or relationship goes upto 1 (one) in mathematical terms. On adding an element of the direction of correlation, it spreads to the maximum extent of –1 to +1 through zero. It can never be more than one. The spread can also be translated into linear shape, as shown in the Fig. 2.8. Correlation of 1 is known as perfect correlation (whether positive and negative). Between the two points of divergent, perfect correlations lies 0 (zero) correlation, a point of no correlation or absence of any correlation between the variables.

Fig. 2.7 is just opposite of this. All the points again fall along a straight line which now runs from the upper left-hand part of the scatter gram to its lower right. It is an example of a perfect negative correlation (with a value of – 1.00). No Correlation (or Zero Correlation) is one when any of the variables in the pair does not respond to the changes in the other, the correlation will come to zero. This is the state of no correlation or zero correlation. This is shown in Fig. 2.9. Seatter plot A shows no correlation when Y does not respond to changes in X. Similarly, zero correlation occurs in Seatter plot B when X does not respond to changes in Y.

Fig. 2.9 : Scatter plot showing No Correlation

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Other Correlations Between the perfect correlations (±1) and zero correlation lies generalised conditions popularly referred to as weak, moderate and strong correlations. These conditions are clearly exhibited in Figs. 2.10, 2.11 and 2.12 respectively. Notice the spreading or the scattering of the plotted points and the assignment of the terms weak, medium and strong to them (generalised terms having no specific limits). Larger is the scattering, weaker is the correlation. Smaller is the scattering, stronger is the correlation, and when the plotted points fall on a straight line, the correlation is perfect (Fig. 2.6 and 2.7).

Fig. 2.10 : Weak Negative Correlation

Fig. 2.11 : Moderate Positive Correlation

Fig. 2.12 : Strong Positive Correlation

Methods of Calculating Correlation There are various methods by which correlation can be calculated. However, under the constraints of time and space, we will discuss the Spearman’s Rank Correlation method only. Spearman’s Rank Correlation

∑ D1

2

Where,

ρ

= rank correlation = sum of the squares of the differences between two sets of ranks

N

= the number of pairs of X-Y

Example 2.9: Calculate Spearman’s Rank Correlation with the help of the following data :

Scores in Economics (X) :

02 08 00 20 12 16 06 18 09 10

Scores in Geography (Y) :

04 12 06 24 16 18 08 20 09 10

29 Processing Data P rocessing

Spearman devised a method of computing correlation with the help of ranks. The method is popularly known as Spearman’s Rank Correlation symbolised as ρ (the Greek letter rho). Spearman’s Rank Correlation method is widely used. The computation of the correlation is undertaken in the steps given below: (i) Copy the data related to X-Y variables given in the exercise and put them in the first and second columns of the table. (ii) Both the variables are to be ranked separately. The ranks of X-variable are to be recorded in column 3 headed by XR (ranks of X). Similarly, the ranks of Y-variable (YR) are to be recorded in the fourth column. The highest value in the data is to be awarded rank one, second highest rank two and so on. Suppose the data for X-variable are 4, 8, 2, 10, 1, 9, 7, 3, 0 and 5, the XR will be 6, 3, 8, 1, 9, 2, 4, 7, 10 and 5 respectively. Notice that the last rank (10 in this case) equals the number of observations. Assignment of YR is also done in the same way. (iii) Now since both XR and YR have been obtained, find the difference between the two sets of ranks (disregarding the sign plus or minus) and record it in the fifth column. The sign of the difference is of no 2 importance, since, these differences are squared in the next operation. 6 D N ( N 2 1) (iv) Each of these differences is squared and sum of this column of squares is obtained. These values are placed in the sixth column. (v) Then the computation of the rank correlation is done by the application of the following equation:

Table 2.8 : Computation of Spearman’s Rank Correlation (1) X 2 8 0 20 12 16 6 18 9 10

(2) Y

(3) XR

(4) YR

(5) D

4 12 6 24 16 18 8 20 9 10

9 7 10 1 4 3 8 2 6 5

10 5 9 1 4 3 8 2 7 6

1 2 1 0 0 0 0 0 1 1

N=10

(6) D2 1 4 1 0 0 0 0 0 1 1 D2=8

Calculation: Where, ρ is Rank Correlation; D is difference between the rank of X and Y; and N is number of items of x – y

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1

6 8 10 102 1

1

48 10 100 1

1

48 10 99

1

48 990

1 0.05 0.95

In rho, we obtain a correlation, which makes a good substitute for other types of correlations, when the number of cases is small. It is almost useless when N is large, because by the time all the data are ranked, other type of correlation could have been calculated.

Excercises 1. Choose the correct answer from the four alternatives given below: (i) The measure of central tendency that does not get affected by extreme values: (a) Mean (b) Mean and Mode (c) Mode (d) Median (ii) The measure of central tendency always coinciding with the hump of any distribution is: (a) Median (b) Median and Mode (c) Mean (d) Mode (iii) A scatter plot represents negative correlation if the plotted values run from: (a) Upper left to lower right (b) Lower left to upper right (c) Left to right (d) Upper right to lower left 2. Answer the following questions in about 30 words: (i) Define the mean. (ii) What are the advantages of using mode ? (iii) What is dispersion ? (iv) Define correlation. (v) What is perfect correlation ? (vi) What is the maximum extent of correlation? 3. Answer the following questions in about 125 words: (i) Explain relative positions of mean, median and mode in a normal distribution and skewed distribution with the help of diagrams. (ii) Comment on the applicability of mean, median and mode (hint: from their merits and demerits). (iii) Explain the process of computing Standard Deviation with the help of an imaginary example.

31

(iv) Which measure of dispersion is the most unstable statistic and why? (vi) What are various steps for the calculation of rank order correlation?

Activity 1. Take an imaginary example applicable to geographical analysis and explain direct and indirect methods of calculating mean from ungrouped data. 2. Draw scatter plots showing different types of perfect correlations.

Processing Data P rocessing

(v) Write a detailed note on the degree of correlation.

You must have seen graphs, diagrams and maps showing different types of data. For example, the thematic maps shown in Chapter 1 of book for Class XI entitled Practical Work in Geography, Part-I (NCERT, 2006) depict relief and slope, climatic conditions, distribution of rocks and minerals, soils, population, industries, general land use and cropping pattern in the Nagpur district, Maharashtra. These maps have been drawn using large volume of related data collected, compiled and processed. Have you ever thought what would have happened if the same information would have been either in tabular form or in a descriptive transcript? Perhaps, it would not have been possible from such a medium of communication to draw visual impressions which we get through these maps. Besides, it would also have been a time consuming task to draw inferences about whatever is being presented in non–graphical form. Hence, the graphs, diagrams and maps enhance our capabilities to make meaningful comparisons between the phenomena represented, save our time and present a simplified view of the characteristics represented. In the present chapter, we will discuss methods of constructing different types of graphs, diagrams and maps.

Representation of Data The data describe the properties of the phenomena they represent. They are collected from a variety of sources (Chapter 1). The geographers, economists, resource scientists and the decision makers use a lot of data these days. Besides the tabular form, the data may also be presented in some graphic or diagrammatic form. The transformation of data through visual methods like graphs, diagrams, maps and charts is called representation of data. Such a form of the presentation of data makes it easy to understand the patterns of population growth, distribution and the density, sex ratio, age–sex composition, occupational structure, etc. within a geographical territory. There is a Chinese proverb that ‘a picture is equivalent to thousands of words’. Hence, the graphic method of the representation of data enhances our understanding, and makes the comparisons easy. Besides, such methods create an imprint on mind for a longer time.

G eneral Rules for Dra wing GGraphs, raphs, Diagrams and MMaps aps Drawing 1. Selection of a Suitable Method Data represent various themes such as temperature, rainfall, growth and distribution of the population, production, distribution and trade of different commodities, etc. These characteristics of the data need to be suitably represented by an appropriate graphical method. For example, data related to the temperature or growth of population between different periods in time and for different countries/states may best be represented using line graphs. Similarly, bar diagrams are suited best for showing rainfall or the production of commodities. The population distribution, both human and livestock, or the distribution of the crop producing areas may suitably be represented on dot maps and the population density using choropleth maps. 2. Selection of Suitable Scale The scale is used as measure of the data for representation over diagrams and maps. Hence, the selection of suitable scale for the given data sets should be carefully made and must take into consideration entire data that is to be represented. The scale should neither be too large nor too small. 3. Design We know that the design is an important cartographic task (Refer ‘Essentials of Map Making’ as discussed in Chapter 1 of the Practical Work in Geography, Part-I (NCERT, 2006), a textbook of Class XI). The following components of the cartographic designs are important. Hence, these should be carefully shown on the final diagram/map. Title

Legend A legend or index is an important component of any diagram/map. It explains the colours, shades, symbols and signs used in the map and diagram. It should also be carefully drawn and must correspond to the contents of the map/diagram. Besides, it also needs to be properly positioned. Normally, a legend is shown either at the lower left or lower right side of the map sheet. Direction The maps, being a representation of the part of the earth’s surface, need be oriented to the directions. Hence, the direction symbol, i. e. North, should also be drawn and properly placed on the final map.

Construction of Diagrams The data possess measurable characteristics such as length, width and volume. The diagrams and the maps that are drawn to represent these data related characteristics may be grouped into the following types:

33 Graphical Representation of Data

The title of the diagram/map indicates the name of the area, reference year of the data used and the caption of the diagram. These components are represented using letters and numbers of different font sizes and thickness. Besides, their placing also matters. Normally, title, subtitle and the corresponding year are shown in the centre at the top of the map/diagram.

(i) One-dimensional diagrams such as line graph, poly graph, bar diagram, histogram, age, sex, pyramid, etc.; (ii) Two-dimensional diagram such as pie diagram and rectangular diagram; (iii) Three-dimensional diagrams such as cube and spherical diagrams. It would not be possible to discuss the methods of construction of these many types of diagrams and maps primarily due to the time constraint. We will, therefore, describe the most commonly drawn diagrams and maps and the way they are constructed. These are : • Line graphs • Bar diagrams • Pie diagram • Wind rose and star diagram • Flow Charts Line Graph The line graphs are usually drawn to represent the time series data related to the temperature, rainfall, population growth, birth rates and the death rates. Table 3.1 provides the data used for the construction of Fig 3.2. Construction of a Line Graph

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(a) Simplify the data by converting it into round numbers such as the growth rate of population as shown in Table 3.1 for the years 1961 and 1981 may be rounded to 2.0 and 2.2 respectively. (b) Draw X and Y-axis. Mark the time series variables (years/months) on the X axis and the data quantity/value to be plotted (growth of population in per cent or the temperature in 0C) on Y axis. (c) Choose an appropriate scale and label it on Y-axis. If the data involves a negative figure then the selected scale should also show it as shown in Fig. 3.1.

Fig. 3.1 : Construction of a Line Graph

(d) Plot the data to depict year/month-wise values according to the selected scale on Y-axis, mark the location of the plotted values by a dot and join these dots by a free hand drawn line.

Example 3.1 : Construct a line graph to represent the data as given in Table 3.1: Table 3.1 : Growth rate of Population in India - 1901 to 2001 Year

Growth rate in percentage

1901 1911 1921 1931 1941 1951 1961 1971 1981 1991 2001

0.56 -0.30 1.04 1.33 1.25 1.96 2.20 2.22 2.14 1.93

35

Activity Find out the reasons for sudden change in population between 1911 and 1921as shown in Fig. 3.2. Polygraph Polygraph is a line graph in which two or more than two variables are shown by an equal number of lines for an immediate comparison, such as the growth rate of different crops like rice, wheat, pulses or the birth rates, death rates and life expectancy or sex ratio in different states or countries. A different line pattern such as straight line ( ____ ), broken line (- - - ), dotted line (……) or a combination of dotted and broken line (-.-.-) or line of different colours may be used to indicate the value of different variables (Fig 3.3).

Graphical Representation of Data

Fig. 3.2 : Annual Growth of Population in India 1901-2001

Example 3.2 : Construct a polygraph to compare the growth of sex-ratio in different states as given in the Table 3.2 : Table 3.2 : Sex-Ratio (Female per 1000 male) of Selected Sates – 1961-2001 States/UT

1961

Delhi Haryana Uttar Pradesh

785 868 907

1971

1981

1991

2001

801 867 876

808 870 882

827 86 876

821 846 898

36 P ractical W ork in Geography, P art-II Work Part-II

Fig. 3.3 : Sex-Ratio of Selected States 1961-2001

Bar Diagram The bar diagrams are drawn through columns of equal width. It is also called a columnar diagram. Following rules should be observed while constructing a bar diagram: (a) The width of all the bars or columns should be similar. (b) All the bars should be placed on equal intervals/distance. (c) Bars may be shaded with colours or patterns to make them distinct and attractive. The simple, compound or polybar diagram may be constructed to suit the data characteristics. Simple Bar Diagram A simple bar diagram is constructed for an immediate comparison. It is advisable to arrange the given data set in an ascending or descending order and plot the data variables accordingly. However, time series data are represented according to the sequencing of the time period. Example 3.3 : Construct a simple bar diagram to represent the rainfall data of Tiruvanantapuram as given in Table 3.3 :

Table 3.3 : Average Monthly Rainfall of Tiruvanantapuram Months

J

F

Rainfall in cm 2.3 2.1

M

A

M

J

J

A

S

O

N

D

3.7 10.6 20.8 35.6 22.3 14.6 13.8 27.3 20.6 7.5

Construction Draw X and Y-axes on a graph paper. Take an interval of 5 cm and mark it on Yaxis to plot rainfall data in cm. Divide X-axis into 12 equal parts to represent 12 months. The actual rainfall values for each month will be plotted according to the selected scale as shown in Fig. 3.4.

37 Fig. 3.4 : Average Monthly Rainfall of Tiruvanantapuram

The line and bar graphs as drawn separately may also be combined to depict the data related to some of the closely associated characteristics such as the climatic data of mean monthly Table 3.4 : Average monthly Temperature temperatures and rainfall. In and Rainfall in Delhi doing so, a single diagram is drawn in which months are Months Temp. in °C Rainfall in cm. represented on X-axis while Jan. 14.4 2.5 temperature and rainfall data Feb. 16.7 1.5 are shown on Y-axis at both Mar. 23.30 1.3 sides of the diagram. Apr. 30.0 1.0 Example 3.4 : Construct a line graph and bar diagram to represent the average monthly rainfall and temperature data of Delhi as given in Table 3.4 :

May June Jul. Aug. Sep. Oct. Nov. Dec.

33.3 33.3 30.0 29.4 28.9 25.6 19.4 15.6

1.8 7.4 19.3 17.8 11.9 1.3 0.2 1.0

Graphical Representation of Data

Line and Bar Graph

Construction (a) Draw X and Y-axes of a suitable length and divide X-axis into 12 parts to show months in a year. (b) Select a suitable scale with equal intervals of 5° C or 10° C for temperature data on the Y-axis and label it at its right side. (c) Similarly, select a suitable scale with equal intervals of 5 cm or 10 cm for rainfall data on the Y-axis and label at its left side. (d) Plot temperature data using line graph and the rainfall by columnar diagram as shown in Fig. 3.5.

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Fig. 3.5 : Temperature and Rainfall in Delhi

Multiple Bar Diagram Multiple bar diagrams are constructed to represent two or more than two variables for the purpose of comparison. For example, a multiple bar diagram may be constructed to show proportion of males and females in the total, rural and urban population or the share of canal, tube well and well irrigation in the total irrigated area in different states. Example 3.5 : Construct a suitable bar diagram to show decadal literacy rate in India during 1951 – 2001 as given in Table 3.5 : Table 3.5 : Literacy Rate in India, 1951-2001 (in %)

Construction (a) Multiple bar diagram may be chosen to represent the above data. (b) Mark time series data on X-axis and literacy rates on Y-axis as per the selected scale.

Year

Literacy Rate Total population

1951 1961 1971 1981 1991 2001

18.33 28.3 34.45 43.57 52.21 64.84

Male 27.16 40.4 45.96 56.38 64.13 75.85

Female 8.86 15.35 21.97 29.76 39.29 54.16

(c) Plot the per cent of total population, male and female in closed columns (Fig 3.6).

Fig. 3.6 : Literacy Rate, 1951-2001

Compound Bar Diagram When different components are grouped in one set of variable or different variables of one component are put together, their representation is made by a compound bar diagram. In this method, different variables are shown in a single bar with different rectangles. 39

Table 3.6 : Gross Generation of Electricity in India (in Billion KWh) Year

Thermal

Hydro

2001-02 2002-03 2003-04

424.4 451.0 472.1

73.5 63.8 75.2

Nuclear 19.5 19.2 17.8

Total 517.4 534.0 565.1

Construction (a) Arrange the data in ascending or descending order. (b) A single bar will depict the gross electricity generation in the given year and the generation of thermal, hydro and nuclear electricity be shown by dividing the total length of the bar as shown in Fig 3.7.

Graphical Representation of Data

Example 3.6 : Construct a compound bar diagram to depict the data as shown in Table 3.6 :

Pie Diagram Pie diagram is another graphical method of the representation of data. It is drawn to depict the total value of the given attribute using a circle. Dividing the circle into corresponding degrees of angle then represent the sub– sets of the data. Hence, it is also called as Divided Circle Diagram. The angle of each variable is calculated using the following formulae. Fig. 3.7 : Gross Electricity Generation in India

Value of given State/Region X 360 Total Value of All States/Regions If data is given in percentage form, the angles are calculated using the given formulae. Percentage of x X 360 100

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For example, a pie diagram may be drawn to show total population of India along with the proportion of the rural and urban population. In this case the circle of an appropriate radius is drawn to represent the total population and its sub-divisions into rural and urban population are shown by corresponding degrees of angle. Example 3.7: Represent the data as given in Table 3.7 (a) with a suitable diagram. Calculation of Angles

Table 3.7 (a) : India’s Export to Major Regions of the World in 2004-05 Unit/Region European Union North America Australia OPEC African Countries Asian Countries Others

% of Indian Export 21.1 19.2 3.7 15 3.3 27.6 10.1

(a) Arrange the data on percentages of Indian exports in an ascending order. (b) Calculate the degrees of Total 100 angles for showing the given values of India’s export to major regions/countries of the world, Table 3.7 (b). It could be done by multiplying percentage with a constant of 3.6 as derived by dividing the total number of degrees in a circle by 100, i. e. 360/100.

(c) Plot the data by dividing the circle into the required number of divisions to show the share of India’s export to different regions/countries (Fig. 3.8). Table 3.7 (b) : India’s Export to Major Regions of the World in 2004-05 Countries African Countries Australia others OPEC Countries North America European Union Asian Countries Total

% 3.3 3.7 10.1 15 19.2 21.1 27.6

Calculation 3.3 x 3.6 = 11.88 3.7 x 3.6 = 13.32 10.1 x 3.6 = 36.36 15 x 3.6 = 54 19.2 x 3.6 = 69.12 21.1 x 3.6 = 75.96 27.6 x 3.6 = 99.36

100

Degree 12º 13º 36º 54º 69º 76º 100º 360º

Construction (a) Select a suitable radius for the circle to be drawn. A radius of 3, 4 or 5 cm may be chosen for the given data set. (b) Draw a line from the centre of the circle to the arc as a radius. (c) Measure the angles from the arc of the circle for each category of vehicles in an ascending order clock-wise, starting with smaller angle. (d) Complete the diagram by adding the title, sub – title, and the legend. The legend mark be chosen for each variable/category and highlighted by distinct shades/ colours. Precautions

Fig. 3.8 : Direction of Indian Exports 2004-05

41 Graphical Representation of Data

(a) The circle should neither be too big to fit in the space nor too small to be illegible. (b) Starting with bigger angle will lead to accumulation of error leading to the plot of the smaller angle difficult.

Flow Maps/Chart Flow chart is a combination of graph and map. It is drawn to show the flow of commodities or people between the places of origin and destination. It is also called as Dynamic Map. Transport map, which shows number of passengers, vehicles, etc., is the best example of a flow chart. These charts are drawn using lines of proportional width. Many government agencies prepare flow maps to show density of the means of transportation on different routes. The flow maps/ charts are generally drawn to represent two the types of data as given below: 1. The number and frequency of the vehicles as per the direction of their movement 2. The number of the passengers and/or the quantity of goods transported. Requirements for the Preparation of a Flow Map

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(a) A route map depicting the desired transport routes along with the connecting stations. (b) The data pertaining Table 3.8 : No. of trains of selected routes of to the flow of goods, Delhi and adjoining areas services, number of vehicles, etc., along S. Railway No. of with the point of origin No. Routes Trains and destination of the 1. Old Delhi – New Delhi 50 movements. 2. New Delhi-Nizamuddin 40 (c) The selection of a 3. Nizamuddin-Badarpur 30 scale through which 4. Nizamuddin-Sarojini Nagar 12 the data related to 5. Sarojini Nagar – Pusa Road 8 the quantity of 6. Old Delhi – Sadar Bazar 32 passengers and 7. Udyog Nagar-Tikri Kalan 6 goods or the number 8. Pusa Road – Pehladpur 15 of vehicles is to be 9. Sahibabad-Mohan Nagar 18 represented. Example 3.10 : Construct a flow map to represent the number of trains running in Delhi and the adjoining areas as given in the Table 3.8.

10. 11. 12. 13. 14. 15. 16.

Old Delhi – Silampur Silampur – Nand Nagari Silampur -Mohan Nagar Old Delhi-Shalimar Bagh Sadar Bazar -Udyog Nagar Old Delhi – Pusa Road Pehladpur – Palam Vihar

33 12 21 16 18 22 12

Construction (a) Take an outline map of Delhi and adjoining areas in which railway line and the nodal stations are depicted (Fig.3.9). (b) Select a scale to represent the number of trains. Here, the maximum number is 50 and the minimum is 6. If we select a scale of 1cm = 50 trains, the maximum and minimum numbers will be represented by a strip of 10 mm and 1.2 mm thick lines respectively on the map. (c) Plot the thickness of each strip of route between the given rail route (Fig. 3.10).

(d) Draw a terraced scale as legend and choose distinct sign or symbol to show the nodal points (stations) within the strip.

Fig. 3.9 : Map of Delhi

Sa

da

Nandnagari

B ar

az

Tikri Kalan Udyog Nagar

Old Delhi Silampur

Ro

ad

Mohan Nagar

lhi De

Pu

sa

w Ne

Nizamuddin

Palam Vihar

Badarpur

50 30

20

10

5

No. Of Trains

Fig. 3.10 : Traffic (Railway) Flow Map of Delhi

Graphical Representation of Data

r

40

43

Shalimar Bagh

Example 3.10 : Construct a water flow map of Ganga Basin as shown in Fig. 3.11.

17

23

13

42

19

50

57

66

Fig. 3.11 : Ganga Basin

Construction (a) Take a scale as a strip of 1cm width = 50,000 cusecs of water. (b) Make the diagram as shown in Fig. 3.12.

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000,Cusecs of water 50

40

30

20

10

5

Fig. 3.12 : Construction of a Flow Map

Thematic Maps Graphs and diagrams serve a useful purpose in providing a comparison between the internal variations within the data of different characteristics represented. However, the use of graphs and diagrams, at times, fails to produce a regional perspective. Hence, variety of maps may also be drawn to understand the patterns

of the regional distributions or the characteristics of variations over space. These maps are also known as the distribution maps. Requirements for Making a Thematic Map (a) State/District level data about the selected theme. (b) Outline map of the study area alongwith administrative boundaries. (c) Physical map of the region. For example, physiographic map for population distribution and relief and drainage map for constructing transportation map. Rules for Making Thematic Maps (i) The drawing of the thematic maps must be carefully planned. The final map should properly reflect the following components: a. Name of the area b. Title of the subject-matter c. Source of the data and year d. Indication of symbols, signs, colours, shades, etc. e. Scale (ii) The selection of a suitable method to be used for thematic mapping.

Classification of Thematic Maps based on Method of Construction

Dot Maps The dot maps are drawn to show the distribution of phenomena such as population, cattle, types of crops, etc. The dots of same size as per the chosen scale are marked over the given administrative units to highlight the patterns of distributions. Requirement (a) An administrative map of the given area showing state/district/block boundaries.

45 Graphical Representation of Data

The thematic maps are generally, classified into quantitative and non-quantitative maps. The quantitative maps are drawn to show the variations within the data. For example, maps depicting areas receiving more than 200 cm, 100 to 200 cm, 50 to 100 cm and less than 50 cm of rainfall are referred as quantitative maps. These maps are also called as statistical maps. The non-quantitative maps, on the other hand, depict the non–measurable characteristics in the distribution of given information such as a map showing high and low rainfall-receiving areas. These maps are also called as qualitative maps. It would not be possible to discuss drawing these different types of thematic maps under the constraint of time. We will, therefore, confine to discuss the methods of the construction of the following types of quantitative maps : (a) Dot maps (b) Choropleth maps (c) Isopleth maps

(b) Statistical data on selected theme for the chosen administrative units, i.e., total population, cattle etc. (c) Selection of a scale to determine the value of a dot. (d) Physiographic map of the region especially relief and drainage maps. Precaution (a) The lines demarcating the boundaries of various administrative units should not be very thick and bold. (b) All dots should be of same size. Example 3.12 : Construct a dot map to represent population data as given in Table 3.9. Table 3.9 : Population of India, 2001 Sl. No.

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1. 2. 3. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30.

States/Union Territories Jammu & Kashmir Himachal Pradesh Punjab Uttaranchal Haryana Delhi Rajasthan Uttar Pradesh Bihar Sikkim Arunachal Pradesh Nagaland Manipur Mizoram Tripura Meghalaya Assam West Bengal Jharkhand Orissa Chhattisgarh Madhya Pradesh Gujarat Maharashtra Andhra Pradesh Karnataka Goa Kerala Tamil Nadu

Total Population 10,069,917 6,077,248 24,289,296 8,479,562 21,082,989 13,782,976 56,473,122 166,052,859 82,878,796 540,493 1,091,117 1,988,636 2,388,634 891,058 3,191,168 2,306,069 26,638,407 80,221,171 26,909,428 36,706,920 20,795,956 60,385,118 50,596,992 96,752,247 75,727,541 52,733,958 1,343,998 31,838,619 62,110,839

No. of dots 100 60 243 85 211 138 565 1,660 829 5 11 20 24 89 32 23 266 802 269 367 208 604 506 968 757 527 13 318 621

47 Graphical Representation of Data

Fig. 3.13 : Population of India, 2001

Construction (a) Select the size and value of a dot. (b) Determine the number of dots in each state using the given scale. For example, number of dots in Maharashtra will be 9,67,52,247/100,000 = 967.52. It may be rounded to 968, as the fraction is more than 0.5. (c) Place the dots in each state as per the determined number in all states. (d) Consult the physiographic/relief map of India to identify mountainous, desert, and/or snow covered areas and mark lesser number of dots in such areas. Choropleth Map The choropleth maps are also drawn to depict the data characteristics as they are related to the administrative units. These maps are used to represent the density of population, literacy/growth rates, sex-ratio, etc. Requirement for drawing Choropleth Map (a) A map of the area depicting different administrative units. (b) Appropriate statistical data according to administrative units. Steps to be followed

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(a) Arrange the data in ascending or descending order. (b) Group the data into 5 categories to represent very high, high, medium, low and very low concentrations. (c) The interval between the categories may be identified on the following formulae i.e. Range/5 and Range = maximum value – minimum value. (d) Patterns, shades or colour to be used to depict the chosen categories should be marked in an increasing or decreasing order. Example 3.13: Construct a Choropleth map to represent the literacy rates in India as given in Table 3.10. Construction (a) Arrange the data in ascending order as shown above. (b) Identify the range within the data. In the present case, the states recording the lowest and highest literacy rates are Bihar (47%) and the Kerala (90.9%) respectively. Hence, the range would be 91.0 – 47.0 = 44.0 (c) Divide the range by 5 to get categories from very low to very high. (44.0/ 5 = 8.80. We can convert this value to a round number, i. e., t 9.0 (d) Determine the number of the categories alongwith range of each category. Add 9.0 to the lowest value of 47.0 as so on. We will finally get following categories : 47 – 56 Very low (Bihar, Jharkhand, Arunachal Pradesh, Jammu and Kashmir) 56 – 65 Low (Uttar Pradesh, Rajasthan, Andhra Pradesh, Meghalaya, Orissa, Assam, Madhya Pradesh, Chhattisgarh)

49 Graphical Representation of Data

Fig. 3.14 : Literacy Rate, 2001

Table 3.10 : Literacy Rate in India, 2001 Original Data on Literacy in India S. No.

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1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35.

States / Union Territories

Literacy Rate

Jammu & Kashmir Himachal Pradesh Punjab Chandigarh Uttaranchal Haryana Delhi Rajasthan Uttar Pradesh Bihar Sikkim Arunachal Pradesh Nagaland Manipur Mizoram Tripura Meghalaya Assam West Bengal Jharkhand Orissa Chhattisgarh Madhya Pradesh Gujarat Daman & Diu Dadra & Nagar Haveli Maharashtra Andhra Pradesh Karnataka Goa Lakshadweep Kerala Tamil Nadu Pondicherry Andaman & Nicobar

55.5 76.5 69.7 81.9 71.6 67.9 81.7 60.4 56.3 47.0 68.8 54.3 66.6 70.5 88.8 73.2 62.6 63.3 68.6 53.6 63.1 64.7 63.7 69.1 78.2 57.6 76.9 60.5 66.6 82.0 86.7 90.9 73.5 81.2 81.3

65 – 74

Data on Literacy in India as arranged in Ascending order S. No. 10. 20. 12. 01. 9. 26. 08. 28. 17. 21. 18. 23. 22. 13. 29. 06. 19. 11. 24. 03. 14. 05. 16. 33. 02. 27. 25. 34. 35. 07. 04. 30. 31. 15. 32.

States / Union Territories

Literacy Rate

Bihar Jharkhand Arunachal Pradesh Jammu & Kashmir Uttar Pradesh Dadra & Nagar Haveli Rajasthan Andhra Pradesh Meghalaya Orissa Assam Madhya Pradesh Chhattisgarh Nagaland Karnataka Haryana West Bengal Sikkim Gujarat Punjab Manipur Uttaranchal Tripura Tamil Nadu Himachal Pradesh Maharashtra Daman & Diu Pondicherry Andaman & Nicobar Delhi Chandigarh Goa Lakshadweep Mizoram Kerala

47.0 53.6 54.3 55.5 56.3 57.6 60.4 60.5 62.6 63.1 63.3 63.7 64.7 66.6 66.6 67.9 68.6 68.8 69.1 69.7 70.5 71.6 73.2 73.5 76.5 76.9 78.2 81.2 81.3 81.7 81.9 82.0 86.7 88.8 90.9

Medium (Nagaland, Karnataka, Haryana, West Bengal, Sikkim, Gujarat, Punjab, Manipur, Uttaranchal, Tripura, Tamil Nadu) 74 – 83 High (Himachal Pradesh, Maharashtra, Delhi, Goa) 83 – 92 Very High (Mizoram, Kerala) (e) Assign shades/pattern to each category ranging from lower to higher hues. (f) Prepare the map as shown in Fig. 3.14. (g) Complete the map with respect to the attributes of map design.

Isopleth Map We have seen that the data related to the administrative units are represented using choropleth maps. However, the variations within the data, in many cases, may also be observed on the basis of natural boundaries. For example, variations in the degrees of slope, temperature, occurrence of rainfall, etc. possess characteristics of the continuity in the data. These geographical facts may be represented by drawing the lines of equal values on a map. All such maps are termed as Isopleth Map. The word Isopleth is derived from Iso meaning equal and pleth means lines. Thus, an imaginary line, which joins the places of equal values, is referred as Isopleth. The more frequently drawn isopleths include Isotherm (equal temperature), Isobar (equal pressure), Isohyets (equal rainfall), Isonephs (equal cloudiness), Isohels (equal sunshine), contours (equal heights), Isobaths (equal depths), Isohaline (equal salinity), etc. Requirement (a) Base line map depicting point location of different places. (b) Appropriate data of temperature, pressure, rainfall, etc. over a definite period of time. (c) Drawing instrument specially French Curve, etc. Rules to be observed (a) An equal interval of values be selected. (b) Interval of 5, 10, or 20 is supposed to be ideal. (c) The value of Isopleth should be written along the line on either side or in the middle by breaking the line.

51

Interpolation

Method of Interpolation For interpolation, follow the following steps: (a) Firstly, determine the minimum and maximum values given on the map. (b) Calculate the range of value i.e. Range = maximum value – minimum value. (c) Based on range, determine the interval in a whole number like 5, 10, 15, etc. The exact point of drawing an Isopleth is determined by using the following formulae. Point of Isopleth

Distance between two points in cm Difference between the two values of corresponding points

Interval

Graphical Representation of Data

Interpolation is used to insert the intermediate values between the observed values of at two stations/locations, such as temperature recorded at Chennai and Hyderabad or the spot heights of two points. Generally, drawing of isopleths joining the places of same value is also termed as interpolation.

The interval is the difference between the actual value on the map and interpolated value. For example, in an Isotherm map of two places show 28º C and 33º C and you want to draw 30º C isotherm, measure the distance between the two points. Suppose the distance is 1cm or 10 mm and the difference between 28 and 33 is 5, whereas 30 is 2 points away from 28 and 3 points behind 33, thus, exact point of 30 will be Thus, isotherm of 30ºC will be plotted 4mm away from 28ºC or 6mm ahead of 33ºC. (d) Draw the isopleths of minimum value first; other isopleths may be drawn accordingly.

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Fig. 3.15 : Drawing of Isopleths

Excercises 1. Choose the right answer from the four alternatives given below: (i) Which one of the following map shows the Population distribution: (a) Choropleth maps (b) Isopleth maps (c) Dot maps (d) Square root map (ii) Which one of the following is best suited to represent the decadal growth of population? (a) Line graph (b) Bar diagram (c) Circle diagram (d) Flow diagram

(iii) Polygraph is constructed to represent: (a) Only one variable (b) Two variables only (c) More than two variables (d) None of the above (iv) Which one of the following maps is known as “Dynamic Map”? (a) Dot map (b) Choropleth (c) Isopleth (d) Flow map 2. Answer the following questions in about 30 words: (i) What is a thematic map? (ii) Differentiate between multiple bar diagram and compound bar diagram. (iii) What are the requirements to construct a dot map? (iv) Describe the method of constructing a traffic flow map. (v) What is an Isopleth map ? How an interpolation is carried out? (vi) Describe and illustrate important steps to be followed in preparing a choropleth map. (vii) Discuss important steps to represent data with help of a pie-diagram.

Activity 1. Represent the following data with the help of suitable diagram.

India : Trends of Urbanisation 1901-2001 Year

0.35 8.27 19.12 31.97 41.42 26.41 38.23 46.14 36.47 31.13

53

2. Represent the following data with the help of suitable diagram.

India : Literacy and Enrolment Ratio in Primary and Upper Primary Schools Year

1950-51 1999-2000

Literacy Ratio

Enrolment Ratio Primary

Enrolment Ratio Upper Primary

Person

Male

Female

Boys

Girls

Total

Boys

Girls

Total

18.3 65.4

27.2 75.8

8.86 54.2

60.6 104

25 85

42.6 94.9

20.6 67.2

4.6 50

12.7 58.8

3. Represent the following data with help of pie-diagram.

Graphical Representation of Data

1911 1921 1931 1941 1951 1961 1971 1981 1991 2001

Decennial growth (%)

India : Land use 1951-2001 1950-51

1998-2001

42 14 17 10 9 8

46 22 14 8 5 5

Net Sown Area Forest Not available for cultivation Fallow Land Pasture and Tree Cultruable Waste Land

4. Study the table given below and draw the given diagrams/maps. Area and Production of Rice in major States States West Bengal Uttar Pradesh Andhra Pradesh Punjab Tamil Nadu Bihar

Area in 000 ha

% to total area

Production 000 tones

5,435 5,839 4,028 2,611 2,113 3,671

12.3 13.2 9.1 5.9 4.8 8.3

12,428 11,540 12,428 9,154 7,218 5,417

% to total production 14.6 13.6 13.5 10.8 8.5 6.4

(a) Construct a multiple bar diagram to show area under rice in each State. (b) Construct a pie-diagram to show the percentage of area under rice in each State. (c)

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Construct a dot map to show the production of rice in each State.

(d) Construct a Choropleth map to show the percentage of production of rice in States. 5. Show the following data of temperature and rainfall of Kolkata with a suitable diagram. Months Jan. Feb. Mar. Apr. May June Jul. Aug. Sep. Oct. Nov. Dec.

Temperature in º C 19.6 22.0 27.1 30.1 30.4 29.9 28.9 28.7 28.9 27.6 23.4 19.7

Rainfall in cm 1.2 2.8 3.4 5.1 13.4 29.0 33.1 33.4 25.3 12.7 2.7 0.4

You have learnt various methods of data processing and representation that you can use to analyse the geographical phenomena in the preceding chapters. You must have observed that these methods are time consuming and tedious. Have you ever thought of a method of data processing and their graphical presentation that can save time and improve efficiency? If you have used a computer for word processing then you must have noticed that the computer is more versatile as it facilitates the onscreen editing of the text, copy and move it from one place to another, or even delete the unwanted text. Similarly, the computer may also be used for data processing, preparation of diagrams/graphs and the drawing of maps, provided you have an access to the related application software. In other words, a computer can be used for a wide range of applications. It must, however, be clearly understood that a computer carries out the instructions it receives from the users. In other words, it cannot perform any function on its own. In the present chapter, we will discuss the use of computers in data processing and mapping.

What can a Computer do? A computer is an electronic device. It consists of various sub-systems like memory, micro-processor, input system and output system. All these sub-systems work together to make it an integrated system. It is an extremely powerful device, which is apt to have an important effect on the systems of data processing, mapping and analysis. A computer is a fast and versatile machine that can perform simple arithmetic operations, such as, addition, subtraction, multiplication, and division and can also solve complex mathematical formulae. It also performs simple logical operations, distinguishing zero from non-zero and plus from minus and discharge the results. In short, a computer is a data processor that can perform substantial computation, including numerous arithmetic or logical operations, without intervention by a human operator during the run.

Provided that you have the basic conceptual clarity, computer can be used very effectively to represent data through maps and diagrams. It makes your job extremely fast. The following advantages of a computer make it distinct from the manual methods: 1. It substantially increases the speed of the computation and data processing. 2. It can handle huge volume of the data, which is normally not possible manually. 3. It facilitates copy, edit, save and retrieve the data at will. 4. It further enables validation, checking and correction of data easily. 5. Aggregation and analysis of data becomes extremely simple. Computer makes it very easy to perform comparative analysis, whether by drawing maps or graphs. 6. The type of graph or map (i.e. bar/pie or types of shades), heading, indexing and other formats can be changed very easily. There are many other advantages that a computer offers, that you will observe yourselves while carrying out your practical work using a computer.

H ardw are CConfiguration onfiguration and SSoftw oftw are RRequirements equirements ardware oftware A computer as an aid to data processing and mapping comprises of hardware and software. The hardware configurations comprise of the storage, display, and input and output sub-systems, whereas software are the programs that are made up of electronic codes. The computer–aided data processing and mapping, hence, requires both hardware components and related application software.

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Hardware The hardware components of a computer include : (a) A Central Processing Unit (CPU) and Storage System (b) A Graphic Display Sub-system (c) Input Devices (d) Output Devices A Central Processing Unit and Storage System The core of modern computers consists of a central processing unit (CPU), which facilitates the execution of program instructions for processing data and controlling peripheral equipments. All data together with the operating system and the application programs occupy space in disk storage unit which functions as working memory. The total storage capacity depends upon the types of activity for which the computer is to be used. The hardware storage capacity for data processing and mapping should be in the range of 1 GB to 4 GB or more and the Random Access Memory (RAM) 32 MB or more. Besides the disk storage, the secondary storage such as floppy disks, CD, pen drives, and magnetic tapes are also used to store permanently large quantities of data that is not actively being processed. The operating system is a basic program, which administers the internal data processing in a computer. The operating systems like MS-DOS, Windows, and UNIX are in general use, with the Windows being the most preferred one.

A Graphic Display System or Monitor A graphic display system or monitor serves as the user’s prime visual communication medium in all computers. A high resolution display system with a greater range of possible display colours and Look–up Tables (LUT) for rapid alteration of colour patterns is generally preferred in graphic and mapping applications. Input Devices The instruction and the statistical data are entered into the computer using the keyboard functions. The keyboard is an important input device that resembles with a typewriter. It has various keys for different purposes. While working on a PC you will notice a flash point on the screen. This is known as cursor. When you press a key on the keyboard, a character is displayed at the point where the cursor is flashing and the cursor moves one position forward. Besides, scanners and digitisers of different size and capabilities are also used for spatial data entry. Output Devices The output devices include a variety of printers such as ink-jet, laser and colour laser printers; and the plotters that are available in different sizes ranging from A3 to A0 size. Computer Software Computer software is a written program that is stored in memory. It performs specific functions as per the instructions given by the user. A data processing and mapping software requires the following modules : • Data Entry and Editing Modules • Coordinate Transformation and Manipulation Modules • Data Display and Output Modules

These inbuilt modules in the data processing and mapping software facilitate the data entry system interface, database creation, error removal, scale and projection manipulations, their organisation, and maintenance of the data. Any of these and other related data entry, editing and management capabilities might be performed using displayed menus and icons on the screen. The present day commercial packages such as MS Excel/Spread sheet, Lotus 1 – 2 – 3, and d – base provide capabilities for data processing and generation of graphs. On the other hand, Arc View/Arc GIS, Geomedia, possess modules for mapping and analysis. Coordinate Transformation and Manipulation Modules The present day softwares provide a wide range of capabilities used to create layers of spatial data, coordinate transformation, editing and linking the spatial data sets with the related non - spatial attributes of data. Data Display and Output Modules The data display and output operations vary over a range of functions and are very much dependent on the skills developed in the field of computer graphics. Some of the common capabilities that the present day softwares provide are:

Processing Use of Computer in Data P rocessing and Mapping

The Data Entry and Editing Modules

57

• Zooming/Windowing to display of selected areas and scale change operation • Colour assignment/change operation • Three dimensional and perspective display • Selective display of various themes • Polygon shading, line styling and point markers display • Output device interface commands for interfacing with plotter devices/ printers • Graphic User Interface (GUI) based menu organisation for an easy interface

C omputer SSoftw oftw are for YYour our UUse se oftware In the preceding paragraphs, a number of data processing softwares have been referred. However, it would be difficult to discuss the capabilities and functions of each one of these softwares under the constraints of time and space. We will, therefore, describe the procedure that is followed in data processing and the preparation of graphs and diagrams using MS Excel or Spreadsheet program. The spreadsheet enables us to feed data, compute various statistics and represent the raw data or computed statistics through graphical methods. MS Excel or Spreadsheet

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As mentioned earlier, MS Excel, Lotus 1 – 2 – 3, and d – base are some of the important softwares used for data processing, and drawing graphs and diagrams. MS Excel being most widely used and commonly available software program in all parts of the country has been chosen among other software to carry out the data processing. Besides, it is also compatible with map-making software as one can easily feed data in MS Excel and attach it to the map-making software to create maps. MS Excel is also called a spreadsheet programme. A spreadsheet is a rectangular table (or grid) to store information. The spreadsheets are located in Workbooks or Excel files. Most of the MS Excel screen is devoted to the display of the worksheet, which consists of rows and columns. The intersection of a row and column is a rectangular area, which is called a cell. In other words, a worksheet is made up of cells. A cell can contain a numerical value, a formula (which after calculation provides numerical value) or text. Texts are generally used for labelling numbers entered in the cells. A value entry can either be a number (entered directly) or result of a formula. The value of a formula will change when the components (arguments) of the formula change. An Excel worksheet contains 16,384 rows, numbered 1 through 1,6384 and 256 columns, represented by default through letters A through Z, AA through AZ, BA through BZ, and continuing to IA through IZ. By default, an Excel workbook consists of three worksheets. If you require, you can insert more, up to 256 worksheets. This means that in the same file/workbook you can store a large number of data and charts. Fig.4.1 shows how an excel workbook looks like.

Fig. 4.1 : MS Excel Workbook

Data Entry and Storing Procedures in Excel

Data Processing and Computation Often raw data need to be processed for further use. You can easily add, subtract, multiply, and divide numbers using the keyboard signs of +, -, *, and /, respectively. These signs are known as operators and they connect elements in a formula or expression. For example, if you want to solve the expression 5 + 6 – 8 – 5, then you can easily work it out in steps below : Step 1 : Click on any cell (with the help of mouse). Step 2 : Type =, followed by the expression. Thus, the expression becomes = 5 + 6 – 8 – 5. Step 3 : Press enter key, and you will get the result in the same cell that you had chosen in Step 1. Note : The numerical operations can only be performed in excel by first typing = sign.

59 Processing Use of Computer in Data P rocessing and Mapping

The data entry and storing procedures are very simple in Excel. You can enter, copy and move any data from one cell to another and save them. You may also delete incorrect or unwanted data entry or a complete file, if it is not required for further use. The elementary functions of Excel that you would require for entering data and storing them are described in Table 4.1. You can learn more on your own by exploring other menus and options by yourself. Further, you will find it easier to feed data if you use the number pad given on the right side of your keyboard. For entering data column-wise, you need to press ‘enter key’ or ‘down arrow’ after typing a number. While row-wise pressing right arrow key after typing a number can enter data.

Table 4.1: Important Functions for Entering and Storing Data Function

Instructions

Menu

Secondary Keyboard Menu (from Shortcuts dropdown list)

1.

For opening a new file

File

New

Ctrl N

For opening an existing file

File

Open

Ctrl O

2.

Save a file

Give a file name and define where you want to store it (by default, it is c:\....\my documents\)

File

Save

Ctrl S

3.

Copy, move Select the set of data and paste a by pressing the left set of data mouse button and dragging it over the set of the data you want to select

Edit

Copy

Ctrl C

4.

Cut, move and paste a set of data

Select the set of data by pressing the left mouse button and dragging it over the set of the data you want to select

Edit

Cut

Ctrl X

60

5.

Paste a set of data

Take the cursor to the cell where you want to paste it

Edit

Paste

Ctrl V

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6.

For undoing the last action*

Edit

Undo

Ctrl Z

7.

For redoing the last action*

Edit

Repeat

Ctrl Y

Note: * You cannot undo or redo any action if you have saved the file after the last action.

These operators that connect elements in a formula are solved in an order. The expressions enclosed in ‘brackets’ are solved first and are followed by the ‘exponents’, ‘division’, ‘multiplication’, ‘addition’ and ‘subtraction’. For example, expression/formula within a cell given as =A8/(A9 + A4) will be solved using Excel as under: It will first add the values entered in cells A9 and A4, and then will divide the value of A8 by the sum. Further, if you want to supplement your understanding on the percentage share of urban population to the total population, in that case, you have to calculate the percentage of urban population in various states of India. To do so, you will require the data on urban population and total population for each

state of India. The worksheet allows you to easily calculate the percentage of urban population in each state provided you adopt the following steps : Step 1 : Step 2 :

Enter the name of the states in first column (i.e. column A). In Column B, corresponding to each state, enter the size of urban population. Step 3 : In Column C, corresponding to respective state enter the size of total population. Step 4 : In Column D and row 2, type = followed by B2/C2 (that is total urban population of Andhra Pradesh divided by the total population in the same State) and *100 (multiplied by 100). Thus, the expression becomes =B2/C2*100 Step 5 : Press enter key. This will give you solution of the expression, that is, the percentage of urban population in Andhra Pradesh. Step 6 : Now you need not to write the formula again for calculating percentage of urban population for other states. Simply, click on the cell D2. This will copy the formula of the first state/cell to all the downward cells you have dragged it over. (Note: the formula =B2/C2*100 that has been written in cell D2, and becomes B3/C3*100 in cell D3, and so on). ‘Fig. 4.2 graphically shows steps 1 to 5 as given above, while step 6 is shown in Fig.4.3.

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Fig. 4.3 : Copying through Dragging over in MS Excel

Processing Use of Computer in Data P rocessing and Mapping

Fig. 4.2 : Cell Operation in MS Excel

You have already been introduced to some basic statistical methods such as measures of central tendency, dispersion and correlation in Chapter 2. You must have understood the concept and rationale behind these techniques. The use of worksheet functions to compute these statistics will be discussed in the subsequent paragraphs. In MS Excel, there are numerous inbuilt statistical and mathematical functions. These functions are located in Insert menu. To use the function, click on the Insert menu, and choose fx (Function) from the dropdown list. Note that your cursor should be located in the cell where you want the formula to appear. Some examples of application of statistical functions are given below. Central Tendencies Central tendencies are represented by mean, median and mode. Arithmetic mean, also called as average, is a commonly used method for calculating the central tendency. In MS Excel, it is denoted by its popular name average. As an example, we shall calculate mean cropping intensity in India during various decades using the average function in Excel. The following steps are to be undertaken : Step 1 : Enter year-wise cropping intensity data in a worksheet, as shown in Fig.4.4. Step 2 :

Click on cell B12 using mouse.

Step 3 :

Click on Insert Menu and choose fx (Function) from dropdown list, this will open Insert Function dialogue box.

Step 4 :

Select Statistical from select a category menu on the dialogue box. This will bring forth the statistical functions available in Excel in the box below in the same dialogue box,

Step 5 :

In the box Select a Function, click on Average, and press OK button. This will open another dialogue box called Function Argument.

Step 6 :

Either enter the cell range of data of the first decade CI_50s (which shows year wise cropping intensity in 1950s) in the Number 1 box on Function Argument dialogue box of data, or drag cursor pressing the left button of mouse over the cell range of data.

Step 7 :

Press OK button on the Function Argument dialogue box. This calculates mean cropping intensity for the decade 1950s in cell B12, where you had put your cursor in the beginning.

Step 8 :

Now calculate the mean for other decade either following Steps 1 – 7 given above or dragging cursor right handward in the same row selecting the small square from rectangle of cell B12 or you can copy the cell B12 and paste it on D12, F12, H12 and J12. This will give you mean value of cropping intensity for the decades 1960s, 1970s, 1980s and 1990s, respectively.

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These steps are further explained in Fig. 4.4 through Fig.4.6.

Fig. 4.4 : Calculation of Mean Using Statistical Function in MS Excel

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Fig. 4.6 : Defining Range in Function Arguments dialogue box

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Fig. 4.5 : Selection of Statistical Function

The computation of mean for the given data reveals that there has been an impressive increase in mean decadal cropping intensity over different decades in general, and 1980s onwards in particular. In fact, during 1980s the “Green Revolution” underwent a spatial spread and a tremendous increase in area under tube-well irrigation took place, which facilitated cultivation in the arid regions as well as during the dry seasons. Using almost the same procedure used for calculating mean, as outlined above, you can calculate median, standard deviation, and correlation. Some hints for this are provided in Fig.4.7 and Fig. 4.8.

Fig. 4.7 : Function for Standard Deviation

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Fig. 4.8 : Function for Correlation

Construction of Graphs You know that the data in tabular form, at times make it difficult to draw inferences about whatever is being presented. On the other hand, the representation of the data in graphical form enhances our capabilities to make meaningful comparisons between the phenomena represented, and present a simplified view of the characteristics depicted. In other words, graphs and diagrams make us to decipher the contents of data easily. For example, it would be difficult to make sense of the Cropping Intensity in India if the data for all Fifty years are presented in tabular form. However, through a line graph or bar diagram, we can easily draw meaningful conclusions about the trend in Cropping Intensity in India. Data Types and Some Suitable Graphical Methods of their Presentation 1. Time series data are represented through line graphs or bar diagram. 2. Bar diagrams and histograms are generally used for showing shares or frequencies of various units. 3. Compound bar diagrams, and pie-charts are used for showing shares of various units. 4. Maps are used for location-wise representation of data. This helps in comprehending spatial patterns in the data.

The selection of a suitable graphical method is very important for the presentation of data. In Chapter 3, you have learnt about graphs and diagrams, and the kind of data suitable for. Here, you will learn how graphs and diagrams are constructed in Excel.

Suppose, you want to represent changes in the share of workers in different industrial categories between 1981 and 2001, the most suitable graphical methods would be bar diagram as it shows changes over different years clearly. The construction of bar diagram requires the following steps : Step 1 : Step 2 :

Enter the data in worksheet as shown in Fig.4.9. Select the cells dragging mouse (right button pressed) over the cells.

Fig. 4.9 : Entering data and selecting cells for Construction of Bar Diagram

Step 3 : Step 4 :

Click on Chart Wizard (Fig.4.9). This will open Step 1 of 4 of Chart Wizard (Fig.4.10). Double click on the simple bar diagram in the box ‘Chart Sub-type’ (Fig.4.10). This will lead you to Step 2 of 4 of Chart Wizard (Fig.4.11), in which worksheet number and selected data range, and a preview of bar diagram appear. As categories in data are arranged row-wise, therefore, it is row-wise chart construction. 65

Step 5 :

Fig. 4.11 : Step 2 of 4 of Chart Wizard

Click on the Next radio button, and this will lead you to Step 3 of 4 of Chart Wizard (Fig.4.12). Here you will find various options for entering ‘title’ ‘name of axes’, options for ‘grid lines’, ‘data labels’ and

Processing Use of Computer in Data P rocessing and Mapping

Fig. 4.10 : Step 1 to 4 of Chart Wizard

‘data table’. Chart Titles and axes name entry are shown in Fig.4.12, while options for ‘legend placement’ are shown in Fig. 4.13. Type the axes names as shown in Fig.4.13 and select the ‘placement of legend’ as shown in Fig.4.14.

Fig. 4.12 : Entering names of Axes

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Fig. 4.13 : Choosing Location of Legend

Step 6 :

Step 7 :

When you have finished entering axes titles and legend options, etc., click on Next radio button (Fig. 4.13). This will lead you to step 4 of 4 of Chart Wizard, which will let you choose the location of the constructed bar diagram for the data (Fig.4.14). Choose ‘As Object in’ and select the same sheet you have entered the data, i.e. Sheet 5 (optionally, you can also place your Bar Diagram in a new sheet choosing ‘as new sheet’). Press OK radio button in Fig. 4.14. This will complete the Chart Wizard and your Bar Diagram as shown in Fig.4.15 will appear in Worksheet 5.

Fig. 4.14 : Choosing Location of Chart

67

You can change the pattern of bars from colours to shades or vice versa by clicking on the bars. Similarly, you can also change the fonts or gridlines if required. The above diagram shows that the share of cultivators has declined significantly over the two decades and the share of other workers has appreciably risen and the shares of agricultural and household labourers have largely been the same. Some Important Norms for Data Representation 1. A figure should have its figure number. 2. It should have a suitable title in which time and space it relates to should also be mentioned. 3. Within title or as sub-title, the unit in which the quantities are shown should be mentioned. 4. The title, sub-title, title of axes, legend and the main presentation should be shown with suitable font size and type so that they occupy space in a balanced manner.

Processing Use of Computer in Data P rocessing and Mapping

Fig. 4.15 : The Complete Bar Diagram

Computer Assisted Mapping The maps may also be drawn using a combination of computer hardware and the mapping software. The computer assisted mapping essentially requires the creation of a spatial database alongwith its integration with attribute or non – spatial data. It further involves verification and structuring of the stored data. What is most important in this context is that the data must be geometrically registered to a generally accepted and properly defined coordinate system and coded so that they can be stored in the internal data base structure within the computer. Hence, care must be taken while using the computer for mapping purposes. Spatial Data The spatial data represent a geographical space. They are characterised by the points, lines and the polygons. The point data represent positional characteristics of the some of the geographical features such as schools, hospitals, wells, tubewells, towns and villages, etc. on the map. In other words, if we want to present occurrence of the objects on a map in dimensionless scale but with reference to location, we use points. Similarly, lines are used to depict linear features like roads, railway lines, canals, rivers, power and communication lines, etc. Polygons are made up of a number of inter-connected lines bounding a certain area and are used to show area features such as administrative units (countries, districts, states, blocks); land use types (cultivated area, forest lands, degraded/waste lands, pastures, etc.) and features like ponds, lakes, etc. Non–Spatial Data

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The data describing the information about spatial data are called as non-spatial or attribute data. For example, if you have a map showing positional location of your school you can attach the information such as the name of the school, subject stream it offers, number of students in each class, schedule of admissions, teaching and examinations, available facilities like library, labs, equipments, etc. In other words, you will be defining the attributes of the spatial data. Thus, nonspatial data are also known as attribute-data. Sources of Geographical Data The geographical data are available in analogue (map and aerial photographs) or digital form (scanned images). The procedure of creating spatial data in the computer has been discussed in Chapter 6.

M apping SSoftw oftw are and their Functions oftware There are a number of commercially available mapping softwares such as ArcGIS, ArcView, Geomedia, GRAM, Idrisi, Geometica, etc. There are also a few freely downloadable softwares that can be downloaded with the help of Internet. However, it would be difficult to discuss the capabilities of each one of these softwares under the constraints of time and space. We will, therefore, describe the procedure in general used in choropleth mapping using a mapping software. A mapping software provides functions for spatial and attribute data input through onscreen digitisation of scanned maps, corrections of errors, transformation of scale and projection, data integration, map design, presentation and analysis.

A digitised map consists of three files. The extensions of these files are shp, shx and dbf. The dbf file is dbase file that contains attribute data and is linked to shx and shp files. The shx and shp files, on the other hand, contain spatial (map) information. The dbf file can be edited in MS Excel. You can construct a choropleth map using any of the mapping software available to you, provided you follow the steps given in the user manual of the given software. If you experiment with the different options available in the software, you would be able to construct several types of maps using different methods.

Excercises 1. Choose the correct option for the alternatives given below : (i) What type of graph would you use to represent the following data? States Madhya Pradesh Goa Karnataka Bihar Orissa Andhra Pradesh Maharashtra (a) Line (c) Pie-diagram

Share of Production of Iron-Ore (in %) 23.44 21.82 20.95 16.98 16.30 0.45 0.04 (b) Multiple bar graph (d) None of the above

(iii) Which is the operator that is calculated first in a formula given in a cell of a worksheet? (a) + (b) – (c) / (d) × (iv) Function Wizard in Excel enables you to: (a) Construct graphs (b) Carry out mathematical/ statistical operations (c) Draw maps (d) None of the above 2. Answer the following questions in about 30 words: (i) What are the functions of different parts of a computer? (ii) What are the advantages of using computer over manual methods of data processing and representation? (iii) What is a worksheet? 3. Answer the following questions in about 125 words: (i) What is difference between spatial and non-spatial data? Explain with examples. (ii) What is the three forms of geographical data?

69 Processing Use of Computer in Data P rocessing and Mapping

(ii) Districts within a state would be represented in which type of spatial data? (a) Points (b) Lines (c) Polygons (d) None of the above

Activity 1. Carry out the following steps using the given data set: (a) Enter the given data in a file and store in ‘My Documents’ folder (Name the file as rainfall). (b) Calculate the standard deviation and mean for the given data set using Function Wizard in Excel spreadsheet. (c) Compute coefficient of variation using the results derived in step (b). (d) Analyse the results. 2. Represent the data given below using a suitable technique with the help of a computer and analyse the graph. Cropping Intensity in India

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Year_80s

CI_80s

Year_90s

CI_90s

1980-81 1981-82 1982-83 1983-84 1984-85 1985-86 1986-87 1987-88 1988-89 1989-90

123.3 124.5 123.2 125.7 125.2 126.7 126.4 127.3 128.5 128.1

1990-91 1991-92 1992-93 1993-94 1994-95 1995-96 1996-97 1997-98 1998-99 1999-00

129.9 128.7 130.1 131.1 131.5 131.8 132.8 134.1 135.4 134.9

You have studied aspects of Physical Geography of the world as well as of India in Class XI. In the present class, besides the Practical Work in Geography you will also study various aspects of Human Geography. While studying these aspects, you may have observed that issues addressed pertain to global or national level. In other words, the given information helps us to understand the issues at macro level. You may also have observed that the forms, events and processes in your surroundings are similar to what you have studied at macro level. Have you ever thought how would you study some of the aspects at local level? You know that the regional level information is used to analyse different physical and human parameters of a large area. Similarly, information has to be gathered at the local level by conducting primary surveys for generating information. The primary surveys are also called field surveys. They are an essential component of geographic enquiry. It is a basic procedure to understand the earth as a home of humankind and are carried out through observation, sketching, measurement, interviews, etc. In the present chapter, we will discuss the procedure involved in carrying out the field surveys.

Wh equired ? Whyy is Field Surv Survee y RRequired Like many other sciences, geography is also a field science. Thus, a geographical enquiry always needed to be supplemented through well –planned field surveys. These surveys enhance our understanding about patterns of spatial distributions, their associations and relationships at the local level. Further, the field surveys facilitate the collection of local level information that is not available through secondary sources. Thus, the field surveys are carried out to gather required information so as the problem under investigation is studied in depth as per the predefined objectives. Such studies also enable the investigator to comprehend the situation and processes in totality and at the place of their occurrence. This is possible through ‘Observation’, which is a useful method of gathering information and then to derive inferences.

Field Surv ocedure Survee y Pr Procedure The field survey is initiated with well-defined procedure. It is performed in the following functionally inter – related stages : 1. Defining the Problem The problem to be studied should be defined precisely. This can be achieved by way of statements indicating the nature of the problem. This should also be reflected in the title and sub-title of the topic of the survey. 2. Objectives A further specification of the survey is done by listing the objectives. Objectives provide outline of the survey and in accordance to these, suitable tools of acquisition of data and methods of analysis will be chosen. 3. Scope Like clearly defined objectives, scope of survey needs to be delimited in terms of geographical area to be covered, time framework of enquiry and if required themes of studies to be covered. This multi-dimensional delimitation of the study is essential in relation to fulfilment of the predefined objectives and limitations of analysis, inferences and their applicability. 4. Tools and Techniques

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(i) Recorded and Published Data

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Field survey is basically conducted to collect information about the chosen problem for which varied types of tools are required. These include secondary information including maps and other data, field observation, data generated by interviewing people through questionnaires.

These data provide base information about the problem. These are collected and published by different government agencies, organisations and other agencies. This information alongwith cadastral and topographical maps, provides basis to prepare the framework of survey. Listing of households, persons, landholdings in the survey area can be done using the official records or electoral rolls available with the village panchayat or the revenue officials. Similarly, essential physical features like relief, drainage, vegetation, land use and cultural features like settlements, transport and communication lines, irrigation infrastructure, etc. can be traced out from the topographical maps. The field boundaries of land parcels can be marked out from cadastral maps available with land revenue officials. The field survey is conducted either for the entire ‘population’ or for the ‘samples’. These basic informations and maps are required to select the units of observation. The large-scale maps of the survey area also help the investigator to orient and locate him/her on the ground. This initial orientation helps the investigator to insert additional features in the map appropriately. (ii) Field Observation The effectiveness of field survey is associated with the investigators capability to collect information about the landscape through observation. The very purpose of field survey is to observe the characteristics and associations of geographic phenomena.

To supplement the observation, certain techniques of acquisition of information are very useful like that of sketching and photography. As you find sketches and photographs provided in your textbooks enhance your comprehension of facts, situations and processes being explained. It is, therefore, essential to learn and apply sketching techniques to capture the prominent features of the landscape to strengthen the explanations. Similarly, landscape scenario can also be captured by photography of the landscape, objects and activities. At times, when suitable large-scale map is not available, a sketch or a notional map of the survey area can be prepared based on reconnaissance survey. This kind of exercise also helps in getting oneself introduced with the area as each feature needs to be observed carefully for locating them in the sketch. All the observations in the field are to be noted down for keeping a systematic record. You cannot memorise every thing you see, feel or understand. Thus, using appropriate scheme of categorising of facts one should record relevant characteristic of objects. While taking notes, a brief interaction with the people or with the members of the field party or referring to recorded information is always required for clarifications and unambiguous recording of observations. (iii) Measurement Some of field surveys demand on site measurement of objects and events. This is all the more necessary when one wants to present the analysis with precision. It involves use of appropriate equipments, which enables the investigator to measure the characteristics precisely. Thus, the field party should carry with them relevant equipment required to measure the selected features such as measuring tape, weighing machine to weigh soil, pH meter or paper strip to measure the acidity or alkalinity and thermometer. (iv) Interviewing

Field Surveys

In all field surveys, dealing with social issues information is gathered through personal interviews. Experiences and knowledge of each individual about his/ her environs as well as about his/her own livings are nothing but information. These experiences, if retrieved efficiently are important sources of information. However, extraction of information through personal interviews is greatly influenced by interviewer’s abilities in terms of understanding of the subject and the people to be interviewed, communicative skills and rapport with the people. (a) Tools : Interviewing of people can be done either through pre-structured questionnaires and schedules or through participatory appraisal methods like social and resource mapping and discussions. (b) Basic Information : While conducting interviews as means of data collection, certain information like that of location, socio-economic background of the respondent are to be noted. On the basis of these parameters, investigator categorises and compiles the information for further computations and analysis. (c) Coverage : During field studies, investigator has to decide whether the survey will be conducted in the form of census for the entire population or will be based on selected sample. If the study area is not very large but composed of diverse elements then entire population should be surveyed. In case of large size area, one can limit the study to selected samples representing all segments of the population.

73

(d)

(e)

(f)

Units of Study : Elements of study need to be defined precisely alongwith the decision about census or sample survey. These elements consist of primary unit of observation like households, parcels of land, business units, etc. Sample Design : A framework of sample survey including its size and method of selecting samples is to be decided in relation to objectives of survey, variations in population and cost and time constraints. Cautions : Field interviews or participatory appraisal methods are highly sensitive activities and should be conducted with utmost sincerity and cautions as one is dealing with human groups which always do not share the cultural ethos and practices that of the investigators. As a student of social science, you should be careful of the larger purpose of the study and should not stretch the argument beyond the scope of the study. To get the correct picture your conversation and behaviour should reflect that you are one of them. While conducting the interview ensure that no other person is intervening in your conversation either by his presence or reply in between.

5. Compilation and Computation You need to organise the information of varied types collected during the fieldwork for their meaningful interpretation and analysis to achieve the set objectives. Notes, field sketches, photographs, case studies, etc. are first organised according to sub-themes of the study. Similarly, questionnaire and schedule based information should be tabulated either on a master sheet or on the spreadsheet. You have already learnt the features and use of spreadsheet. You can even construct indicators and compute descriptive statistics.

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6. Cartographic Applications You have learnt different methods of mapping and drawing of diagrams and graphs and also use of computer in drawing them neatly and accurately. For getting visual impressions of variations in the phenomena, diagrams and graphs are very effective tools. Thus, the description and analysis should be duly supported by these presentations. 7. Presentations The field study report in concise form should contain all the details of the procedures followed, methods, tools and techniques employed. The major part of the report will be devoted to the interpretation and analysis of information gathered and computed alongwith supportive facts in the form of tables, charts, statistical inferences, maps and references. At the end of the report, you should also provide the summary of the investigation. On the basis of above outlines, you will select a problem or topic and carry out the fieldwork as a team of investigators in the supervision of your teacher.

Field Surv ase Studies Survee y : CCase You know that the field survey plays a significant role in understanding the forms, processes and events at local level. A field survey may be conducted to study any issue of general concern. However, the selection of a topic for the case study depends upon the nature and character of the area where the survey is to

be carried out. For example, in low rainfall and agriculturally less productive regions, droughts form a major topic of study. On the other hand, in the States like Assam, Bihar and West Bengal, which experience high rainfall conditions and occurrences of frequent floods during rainy season necessitates a survey for the assessment of the damages caused by the floods. Similarly, a case study on air pollution emerges as a major topic near a smog emitting industrial plant or a survey of the changing patterns of agricultural land use in Punjab and western Uttar Pradesh, which has drawn the benefits of the Green Revolution for several years becomes important. In the present chapter, we will discuss how specific case studies on droughts, and poverty are conducted. These have been selected from case studies given in your syllabus. These are : 1. Ground Water Change 2. Environmental Pollution 3. Soil Degradation 4. Poverty 5. Droughts and Floods 6. Energy Issues 7. Land use survey and Change Detection. A summary of the procedure that could be followed in carrying out the field survey on any of these topics is provided in Table 5.1. Instructions for the Students

Field Study of PPoov erty: Extent, DDeterminants eterminants and CConsequences onsequences The Problem Poverty denotes a state of people in terms of income, assets, consumption or nutrition at a given point of time. It is often understood and conveyed in the context of poverty line, which is a critical threshold level of income, consumption, access to productive resources, and services below which people are classed as poor. The issue of poverty is closely linked with inequality, which is the cause of poverty. Poverty is, thus, not only an absolute but also a relative state. It varies

75 Field Surveys

The students should prepare a blue print of the field survey in consultation with the class teacher to include details of the area to be visited alongwith a map of the area, if available, clear understanding of the objectives of the survey and the well-structured questionnaire. The teacher should also give a few necessary instructions to the students. These include : 1. Be courteous to the people of the area, you are visiting for the field survey. 2. Develop friendly attitude with the people you meet and establish rapport. 3. Ask questions in comprehendible language. 4. Avoid asking the questions that either may hurt the feelings of the people you are interviewing or those that may irritate them. 5. Do not make any promises with the inhabitants of the area and do not tell lies about your purpose. 6. Record each and every detail as given by the respondent of your querries and show them the recorded version if so asked for.

from region to region. However, there is something absolute about it and despite the variations in regions and diversified society, people require adequate levels of food, clothing and shelter. Poverty can be either a chronic or temporary phenomena. The chronic poverty, which is also known as structural poverty, is more crucial to be understood. Another significant aspect of poverty is that in spite of high rate of economic growth more and more people are identified below the poverty line. It is rampant in both rural and urban areas alike. Thus, the dimensions of poverty and its measures could be studied through a field survey. Fig. 5.1 and 5.2 provide a glimpse of poverty-ridden families and the villages. The first step to conduct such a survey is listing of its objectives.

Fig. 5.1 : A Poverty-ridden family

Objectives

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The study of extent, determinants and consequences of poverty can be Fig. 5.2 : A Poverty-ridden Village carried out with the following objectives in mind: 1. To identify appropriate criteria to measure poverty line. 2. To assess the levels of well-being of people in terms of income, assets, expenditure, nutrition, access to resources and services. 3. To explain the state of poverty in relation to historical and structural conditions of the village and its people. 4. To examine the implications of poverty. Coverage The spatial, temporal and thematic aspects of survey be understood clearly. Spatial In order to achieve the aforesaid objectives a field study may be conducted in a selected part of the rural or urban settlements. Spatially, it may cover an area of 200 hectares or more and inhabited by about 400 persons or 100 households. Temporal If the problem pertains to chronic poverty, the study should be based on average conditions or reflecting responses with references to normal rainfall year for the

village as well as for the surrounding area. In case of temporary poverty, current year situations are to be investigated. Thematic Thematically, the study should cover household and individual level aspects like socio-demographic characteristics, permanent and consumer assets, income and expenditure, access to health, educational, transport and power services and infrastructure facilities to capture the targeted issues of status, determinants and implications of poverty. Tools and Techniques Secondary Information Before you proceed for field study, you should go through the literature on poverty and the region in general and the selected village in particular. The conceptual aspects of poverty like its meaning, measurement, criteria, causes, etc. can be understood through published work related to economic development, social changes and economic surveys. Basic population statistics can be obtained from district census handbooks or the village level primary census abstract, agricultural and livestock statistics can be acquired from village revenue official or the Patwari Lekhpal, Karamchari, Karnain, etc. Household lists and other village level information can be collected from Gram Panchayat office. Similarly, other relevant data are available with respective departments located at tehsil or block headquarters. All these informations are essential to build up the framework of the village resources and economy as well as to develop research design including sample design if survey is not to be based on entire population. Maps

Observations As a fundamental tool of field survey, much of the details of poverty scenario can be visualised through keen observation. Observations of the routine activities of the poverty ridden people; quality and quantity of the food items; sources of fuel wood and drinking water; state of clothing and shelter human sufferings associated with malnutrition, hunger, sickness, etc.; locational, social and political deprivations due to poverty and other pertinent attributes can be understood. These observations with aids like photography, sketching, audio-visual recordings, etc. or just in the form of notes are valuable source of non-quantifiable information to validate different point of views and to draw conclusions. Measurement In some situation, actual measurement need to be taken up. This is required in case of non-availability of data pertaining to quantity of food items consumed

77 Field Surveys

Topographic details including relief, drainage, water bodies, settlements, means of communications and other topographical features of a village and its surrounding region are to be traced and studied from 1:50,000 or 1:25,000 scale topographical maps. Similarly, the 1:4,000 scale cadastral maps and revenue records of the villages may be obtained from the revenue officials. These maps provide spatial dimension of inequality in land distribution if plotted by ownership of households.

daily or the state of health in terms of height and weight, quality of drinking water or the nutritional value of different food items, availability of living space, etc. Simpler means of measurement are very fruitful in quantifying certain items precisely. Personal Interview Most of poverty measures are based on aggregate household conditions. Thus, field data collection through interviewing will be at household level. However, information about the household will have to be extracted either from the head of the household or the more responsive and knowledgeable member of the household. Apart from canvassing questionnaires household data will also be collected interviewing village leaders, service providers, institutional heads, etc. to compute relevant indices. Survey Design Survey can be conducted, as census covering all the households of the village if the number of household are manageable with the number of students in the class otherwise a stratified sampling will be appropriate to extract information. Stratification of households can be done on the basis of land holdings classes, social classes, division of settlement into grids or concentric circles. For stratification listing of households alongwith these criteria/attributes and notional map showing the plan of settlement are to be completed as follows : Table 5.1 : List of Households with Basic Attributes of Stratification of Sampling S. Head of Household No. with Father’s Name

Social Class/ Land Category Holding (ha)

78 P ractical W ork in Geography, P art-II Work Part-II

1. Mohanlal S/o Sohanlal Dhaker : OBC 2. Homaji S/o Kaluji 3.

.........

Bheel : ST .........

Location of House (Grid/ Circle Reference)

7.2

A2

0.2

D4

.........

.........

Remarks

Grids or circles in the notional map/plan may be drawn for spatial stratification as shown in Fig. 5.3. Schedule/Questionnaire Interview, observation and at times, measurement based household information is to be enquired and recorded systematically in the pre-designed questionnaire (Please see Annexure 1 A to H). Compilation and Computation Data Entry and Tabulation After completing the survey in the field collected information need to be compiled for further computation and analysis. Now, this task can be accomplished more conveniently in spreadsheet formats, which you have already practised as part of your computer related practical work. For efficient management of these data follow the following sequence :

Index Pucca Building : Residential

"

Non-Residential

Kutcha Building : Residential Non-Residential " Pucca Road Kutcha Road Pathway Railway Line River Canal Tank/Pond Well, Tap, Handpump Temple, Mosque, Gurudwara etc. School, Dispensary, Panchayat Ghar, Post Office etc.

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1. Assign unique identity code to each surveyed household. 2. Similarly, each person in the demographic table will also be assigned unique identity code for compilation in separate spreadsheet. 3. It will be more convenient if each type of household level information is compiled on separate sheet. 4. Unique name to be assigned for each attribute in each column. 5. Information on each sheet will be filled according to household code for further processing. Verification and Consistency Checks After data entry, random verification of entries is necessary to ascertain the correctness of data. This is further checked by cross total and with the help of maximum and minimum values as well as in the light of related variables. Computation of Indices Computation of indices using available value parameters and calculating the ratios is a significant task before analysing the situation of poverty. In this regard,

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Fig. 5.3 : Notional Map of the Settlement with Grids for Sampling

following set of indices may be computed at household level for further analysis : 1. Indices indicating the state of well-being measured on the basis of total assets, total income, total expenditure, food consumption, nutrition level, etc. 2. Indices explaining the reasons of chronic poverty like social class membership and perpetuating legacies, size of household, type of family, type of occupations, educational levels, size of land holdings and state of irrigation, type of crops cultivated, subsidiary sources of employment, ownership of productive assets, state of gender equality, etc. 3. Indices related to consequences of poverty can be computed on the basis of state of gender discrimination, literacy and educational level among the youths and young ones, employment diversification, productive and consumer assets, crop yields, pattern of expenditure and nutritional intakes. It is significant to note that many of the causative factors are also resultant facts due to their circular relationship with poverty. Visual Presentation

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Summarised tables, diagrams and graphs as you learnt as part of cartographic work can be employed to represent the salient characteristics of poverty in the village. For this purpose, tables may be prepared according to land holding categories or the social categories of households including the caste based classifications. Similarly, composite indices of productive assets or total expenditure can be used to segregate households for showing their state of wellbeing. Variations in well-being can also be shown in the form of drawing a poverty line and class-wise distribution of households above and below that line to visualise the poverty-affected sections of the society and their social background. A very significant graphical tool to indicate the inequality is Lorenz curve and it can be drawn to show unequal distribution of assets, income and expenditure among the households of the village. Thematic Mapping Spatial distribution of agricultural as well as non-agricultural land within the revenue limits of the village and in the settlement can be shown by chorochromatic maps to assess the extent of control on natural resources of certain social groups as a source of inequality, and one of the important causes of poverty. Poor accessibility in relation to site of houses and location of services can also be visualised with the help of maps. Statistical Analysis Simple descriptive statistical methods as well as measures of associations, explanatory relationships and composite indices based on household level indicators can be employed meaningfully to draw inferences. In this regard, simple arithmetic mean can indicate the average situation whereas the coefficient of variation will indicate the extent of relative inconsistency in socio-economic well-being among different groups of households. Similarly, you can measure the intensity of relationship between two indices using the coefficient of correlation and explain the probable causes of perpetuation of poverty or its impact on other socio-economic aspects.

Report Writing Finally, using all the analysed material, you will present your report in group or individually as instructed by your teacher in the systematic way as you followed in the investigation of the problem. All the details, we discussed till now will be part of your presentation in the same sequence alongwith major conclusions and inferences you have drawn. You will also enrich your presentation with appropriate illustrations including maps, diagrams, graphs, photographs, sketches, etc. The statement in the text will be duly supported by the facts shown in tabular forms as well as references of earlier works.

Field Study of Droughts : A Study of Belgaum District, Karnataka Some of the regions in India have plenty of water, and shortages are rare. But in many parts of the country, water is scarce and people can never be sure when it will rain next. Droughts happen when for months or even years, the earth’s surface loses more water than it collects. In some places of deserts, it almost never rains at all. Droughts can affect many peoples’ lives. Droughts and floods are two adverse factors, which Indian farmers have to face. A specific definition of any one of them is quite difficult. However, qualitatively, agricultural drought can be defined as a prolonged and acute moisture deficiency. Drought, as commonly understood, is a condition of climatic dryness that is severe enough to reduce soil moisture and water below the minimum limit necessary for sustaining plant, animal and human life (Fig 5.4 and 5.5). It is usually accompanied by hot dry winds and may be followed by damaging floods.

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Fig. 5.4 : Drought Affected Area

Fig. 5.5 : Soil Moisture Loss

Drought has been recognised as one of the main causes of human misery. While generally associated with semiarid or desert conditions, drought can occur in areas that normally enjoy adequate rainfall and moisture levels. In the broadest sense, any lack of water for the normal needs of agriculture, livestock, industry, or human population may be termed a drought. The cause may be lack of supply, pollution of the water, inadequate storage, conveyance facilities, or abnormal demand.

The effects of drought depend on its severity and duration and the size of the affected area. The impact depends on the level of socio-economic development. Societies that are more developed and economically diversified can better adjust to a drought and can recover more quickly. The poor regions, especially those reliant on any crop or pastoral economies, are more severely affected. The worst effects of drought are the dramatic reduction of surface water and loss of food. Crop failures cause a chain reaction of human suffering (hunger and malnutrition) and economic difficulties. In developing countries, these conditions can culminate in a large number of starvation deaths and farmers’ suicides. Objectives A field survey for the assessment and magnitude of the droughts can be carried out with the following objectives in mind : (a) To identify and record areas experiencing recurring drought conditions. (b) To get the first hand experience of droughts as a natural disaster. (c) To suggest drought preparedness measures for the people of the area. Coverage The aspects related to the spatial, temporal and thematic coverage be understood. Spatial In order to achieve the aforesaid objectives, a field study may be conducted of a drought prone area, if it has experienced drought in or around your district. Temporal

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If the problem pertains to recurring droughts, the study should be based on average conditions reflecting responses with references to normal rainfall year for affected area and its surroundings. Besides, the data on agricultural productions for the drought years may be compared with the non–drought year production figures. Thematic Thematically the assessments for the agricultural production and crop land use, rainfall variability and vegetation status should be made to understand the magnitude, determinants and implications of the droughts. Tools and Techniques Secondary Information The maps and the data pertaining to the rainfall, crop production and population should be collected for drought affected areas for the drought years from the following government/ quasi-government offices : (i) Indian Daily Weather Reports, Indian Meteorological Department (IMD), Division of Agricultural Meteorology, Pune (ii) Crop Weather Calendar, IMD, Agrimet Division, Pune (iii) Government of Karnataka, Belgaum District Gazetteers, Bangalore 1987

(iv) Census Handbooks, Census of India, New Delhi (v) District Handbook/Village Directories, Government of Karnataka (vi) Statistical Abstracts, Bureau of Economics and Statistics, Government of Karnataka, Bangalore. Maps 1 : 50,000 and large-scale topographical maps of the drought affected areas enable the identification and mapping of the perennial and non-perennial water bodies, settlements, land use, and other physical and cultural features. Besides, the cadastral maps help in collecting the data about land use. Observation Observation means looking around and talking to people and noting down the observed information about the shortage of water, crop failures, lack of fodder, starvation deaths, farmer’s suicides, if any. (a) Targeted Objects and Processes : A detailed study of the changes in the crop land use pattern of the selected village as well as major rivers, streams, nalla, tanks and wells and irrigation facilities, if any, should be made in the light of the drought situation. (b) Photographs and Sketches : Photographs and sketches of the parched lands, people and livestock can give a qualitative touch to the study if carried out during the field survey. Measurement Objects (to be measured)

Interviewing The questionnaire method involves asking previously framed questions to the person to be interviewed. The surveyor has to ask the question and take down the answer if it is a structured questionnaire. The questions should be related to the drought and economic conditions of the farmers in terms of amount of rainfall received, rainy days, sowing, watering, nature of crops, livestock and fodder, domestic water supply, health care, rural credit and employment and anti-poverty programmes of the government. The degree of feeling of the respondent can be noted on a five–point scale (very good, good, satisfactory, bad and very bad). Tabulation The data collected from the primary and secondary sources has to be organised in a systematic manner for easy processing and interpretation. Different methods are used to quantify the data into groups or heading such as the tally mark method.

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The village, as a unit, is selected for this type of survey. A cadastral map is obtained from the village patwari. This map shows the Khasra numbers and boundaries of the fields. Some copies of the outline map are prepared and information filled in. These include the wells, tanks, and streams in terms of depth of water, limits of perennial water in larger streams; sowing in the total number of fields, loss of seeds, harvesting; availability of drinking water facilities; official relief measures, etc.

Presentation of Report The information gathered during field survey is finally recorded in the form of a detailed report about the cause and magnitude of the drought and its impact on the economy and life of the people.

Excercises 1. Choose the right answer from the four alternatives given below : (i) Which one of the following helps most in planning for a field survey ? (a) Personal Interviews (b) Secondary Information (c) Measurements (d) Experimentation (ii) Which one of the following is taken up at the conclusion of a field survey ? (a) Data entry and Tabulation (b) Report Writing (c) Computation of Indices (d) None of the above (iii) What is most important at the initial stages of field survey ? (a) Outlining the Objectives (b) Collection of Secondary Information (c) Defining the spatial and thematic coverages (d) Sample Design (iv) What level of information is acquired during a field survey ? (a) Macro level information (b) Maso level information (c) Micro level information (d) All of the above levels of information 2. Answer the following questions in about 30 words :

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(i) Why is a field survey required ? (ii) List the tools and techniques used during a field survey.

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(iii) What type of coverages need to defined before undertaking a field survey? (iv) Describe survey design in brief. (v) Why is the well-structured questionnaire important for a field survey ? 3. Design a field survey on any one of the following problems : (a) (b) (c) (d) (e)

Environmental Pollution Soil Degradation Floods Energy Issues Land Use Change Detection

You know that the computers enhance our capabilities in data processing and in drawing graphs, diagrams and maps (Refer Chapter 4 of the present book). The disciplines that deals with the principles and methods of data processing and mapping using a combination of computer hardware and the application software are referred as the Database Management System (DBMS) and the Computer– Assisted Cartography respectively. However, the role of such computer applications is restricted to merely processing of the data and their graphical presentation. In other words, the data so processed or the maps and diagrams so prepared could not be used to evolve a decision support system. As a matter of fact, there are several questions that we normally encounter in our day-to-day life and look for satisfactory solutions. These questions may be : What is where ? Why is it there ? What will happen if it is shifted to a new location ? Who will be benefited by such a reallocation? Who are expected to loose the benefits if reallocation takes place? In order to, understand these and many other questions we need to capture the necessary data collected from different sources and integrate them using a computer that is supported by geo–processing tools. Herein lays the concept of a Spatial Information System. In the present chapter, we will discuss basic principles of the Spatial Information Technology and its extension to the Spatial Information System, which is more commonly known as Geographical Information System.

What is Spatial Information Technology? The word spatial is derived from space. It refers to the features and the phenomena distributed over a geographically definable space, thus, having physically measurable dimensions. We know that most data that are used today have spatial components (location), such as an address of a municipal facility, or the boundaries of an agricultural holdings, etc. Hence, the Spatial Information Technology relates to the use of the technological inputs in collecting, storing, retrieving, displaying, manipulating, managing and analysing the spatial information. It is an amalgamation of Remote Sensing, GPS, GIS, Digital Cartography, and Database Management Systems.

What is GIS (Geographical Information System)? The advance computing systems available since mid 1970’s enable the processing of georeferenced information for the purpose of organising spatial and attribute data and their integration; locating specific information in individual files and executing the computations, performing analysis and evolving a decision support system. A system capable of all such functions is called Geographic Information System (GIS). It is defined as A system for capturing, storing, checking, integrating, manipulating, analysing and displaying data, which are spatially referenced to the Earth. This is normally considered to involve a spatially referenced computer database and appropriate applications software. It is an amalgamation of Computer Assisted Cartography and Database Management System and draws conceptual and methodological strength from both spatial and allied sciences such as Computer Science, Statistics, Cartography, Remote Sensing, Database Technology, Geography, Geology, Hydrology, Agriculture, Resource Management, Environmental Science, and Public Administration. Forms of Geographical Information As discussed in Chapter 4, two types of the data represent the geographical information. These are spatial and non – spatial data (Box 6.1). The spatial data are characterised by their positional, linear and areal forms of appearances (Fig. 6.1). Box 6.1 : Spatial and non-spatial data Stock Register of a Cycle shop Part No.

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Quantity

Description

Literate Population in States 1981 State

% Male

% Female

101435

54

Wheel Spoke Kerala

75.3

65.7

108943

68

Ball Bearing

Maharashtra

58.8

34.8

105956

25

Wheel Rim

Gujarat

54.4

32.3

123545

108

Tyre

Punjab

47.2

33.7

Geographic Database : A database contains attributes and their value or class. The non-spatial data on the left display cycle parts, which can be located anywhere. The data record on the right is spatial because one of the attributes, the name of different states, which have a definite locations in a map. This data can be used in GIS.

Fig. 6.1 : The Point, a Line and an Area Feature

These data forms must be geometrically registered to a generally accepted and properly defined coordinate system and coded so that they can be stored in the internal data base structure of GIS. On the other hand, the data those describe the spatial data are called as Non–Spatial or attribute data. The spatial data are the most important pre-requisite in a spatial or geographical information system. In a GIS core, it could be built in several ways. These are : • Acquire data in digital form from a data supplier • Digitise existing analogue data • Carry out one’s own surveys of geographic entities. The choice of a source of geographical data for a GIS application is, however, largely governed by : • The application area in itself • The available budget, and • The type of data structure, i.e. vector/raster. For many users, the most common source of spatial data is topographical or thematic maps in hard copy (paper) or soft copy form (digital). All such maps are characterised by : • A definite scale which provides relationship between the map and the surface it represents, • Use of symbols and colours which defines attributes of entities mapped, and • An agreed coordinate system, which defines the location of entities on the Earth’s surface.

The maps, irrespective of a graphic medium of communication of geographic information and possessing geometric fidelity, are inherited with the following limitations : (i) Map information is processed and presented in a particular way. (ii) A map shows a single or more than one predetermined themes. (iii) The alteration of the information depicted on the maps require a new map to be drawn. Contrarily, a GIS possesses inherent advantages of separate data storage and presentation. It also provides options for viewing and presenting the data in several ways. The following advantages of a GIS are worth mentioning : 1. Users can interrogate displayed spatial features and retrieve associated attribute information for analysis. 2. Maps can be drawn by querying or analysing attribute data. 3. Spatial operations (Polygon overlay or Buffering) can be applied on integrated database to generate new sets of information. 4. Different items of attribute data can be associated with one another through shared location code.

Technology Spatial Information T echnology

Adv antages of GIS oovv er MManual anual MMethods ethods dvantages

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Components of GIS The important components of a Geographical Information System include the followings : (a) Hardware (b) Software (c) Data (d) People The different components of GIS are shown in Fig. 6.2. Hardware As discussed in Chapter 4 the GIS has three major components : • Hardware comprising of the processing storage, display, and input and output sub-systems. • Software modules for data entry, editing, maintenance, analysis, transformation, manipulation, data display and outputs. • Database management system to take care of the data organisation. Software An application software with the following functional modules is important prerequisite of a GIS : • Software related to data entry, editing and maintenance • Software related to analysis/transformation/manipulation • Software related to data display and output.

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Data Spatial data and related tabular data are the backbone of GIS. The existing data may be acquired from a supplier or a new data may be created/collected inhouse by the user. The digital map forms the basic data input for GIS. Tabular data related to the map objects can also be attached to the digital data. A GIS will integrate spatial data with other data resources and can even use a DBMS.

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People GIS users have a very wide range from hardware and software engineers to resources and environmental scientists, policy makers, and the monitoring and implementing agencies. These cross-section of people use GIS to evolve a decision support system and solve real time problems.

Fig. 6.2 : Basic Components of GIS

Spatial DData ata FFormats ormats The spatial data are represented in raster and vector data formats : Raster Data Format Raster data represent a graphic feature as a pattern of grids of squares, whereas vector data represent the object as a set of lines drawn between specific points. Consider a line drawn diagonally on a piece of paper. A raster file would represent this image by sub-dividing the paper into a matrix of small rectangles, similar to a sheet of graph paper called cells. Each cell is assigned a position in the data file and given a value based on the attribute at that position. Its Fig. 6.3 : Generic Structure for a Grid row and column coordinates may identify any individual pixel (Fig. 6.3). This data representation allows the user to easily reconstruct or visualise the original image. The relationship between cell size and the number of cells is expressed as the resolution of the raster. The effect of grid size on data in raster format is explained in Fig. 6.4.

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Fig. 6.4 : Effect of Grid Size on Data in Raster Format

The Raster file formats are most often used for the following activities : • For digital representations of aerial photographs, satellite images, scanned paper maps, and other applications with very detailed images. • When costs need to be kept down. • When the map does not require analysis of individual map features. • When “backdrop” maps are required. Vector Data Format A vector representation of the same diagonal line would record the position of the line by simply recording the coordinates of its starting and ending points. Each point would be expressed as two or three numbers (depending on whether the representation was 2D or 3D, often referred to as X,Y or X,Y,Z coordinates) (Fig. 6.5). The first number, X, is the distance between the point and the left side of the paper; Y, the distance between the point and the bottom of the paper; Z, the point’s elevation above or below the paper. Joining the measured points forms the vector.

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Fig. 6.5 : The Vector Data Model is based around Coordinate Pairs

A vector data model uses points stored by their real (earth) coordinates. Here lines and areas are built from sequences of points in order. Lines have a direction to the ordering of the points. Polygons can be built from points or lines. Vectors can store information about topology. Manual digitising is the best way of vector data input. The Vector files are most often used for : • Highly precise applications • When file sizes are important • When individual map features require analysis • When descriptive information must be stored The advantages and the disadvantages of the raster and vector data formats are explained in Box 6.2.

Box 6.2 : Comparison of Raster and Vector Data Formats Raster Model

Vector Model

Advantages • Simple data structure • Easy and efficient overlaying • Compatible with RS imagery • High spatial variability is efficiently represented • Simple for own programming • Same grid cells for several attributes

Advantages • Compact data structure • Efficient for network analysis • Efficient projection transformation • Accurate map output

Disadvantages • Inefficient use of computer storage • Errors in perimeter and shape • Difficult network analysis • Inefficient projection transformations • Loss of information when using large cells Less accurate (although interactive) maps

Disadvantages • Complex data structure • Difficult overlay operations • High spatial variability is inefficiently represented • Not compatible with RS imagery

Raster entities

Real world entities

Vector entities Y

X

Points-Hotel

91

Y

X Y

X

Areas - Forest Y

X

Network-Roads Y

Surface-Elevation

X

Fig. 6.6 : Representation of Spatial Entities in Raster and Vector Data Formats

Technology Spatial Information T echnology

Lines-Electric Supply Lines

S equen ce of GIS AActivities ctivities equence The following sequence of the activities are involved in GIS related work : 1. Spatial data input 2. Entering of the attribute data 3. Data verification and editing 4. Spatial and attribute data linkages 5. Spatial analysis Spatial Data Input As already mentioned, the spatial database into a GIS can be created from a variety sources. These could be summarised into the following two categories : (a) Acquiring Digital Datasets From a Data Supplies

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The present day data supplies make the digital data readily available, which range from small-scale maps to the large-scale plans. For many local governments and private, such data form an essential source and keep such groups of users free from overheads of digitising or collecting their own data. Although, using such existing data sets is attractive and time saving, serious attention must be paid to data compatibility when data from different sources/supplies are combined in one project. The differences in terms of projection, scale, base level and description in attributes may cause problems. At a practical level, users must consider the following characteristics of the data to ensure that they are compatible with the application: • The scale of the data • The geo-referencing system used • The data collection techniques and sampling strategy used • The quality of data collected • The data classification and interpolation methods used • The size and shape of the individual mapping units • The length of the record. It must also be noted that where data are used from a number of sources, and particularly where the area of study crosses administrative boundaries, the difficulties in data integration are caused by different geographical referencing systems, data classification and sampling. Hence, the user needs to be aware of these problems, which are particularly prone when compiling inter province, and inter-district data sets. Once, the compatibility between the data acquired from different suppliers is established, the next stage involves the transfer of data from a medium of transfer to the GIS. The use of DAT tapes, CD ROMS and floppy disks is becoming increasingly common for the purpose. At this stage, the conversion from encoding and structuring system of the source to that of GIS to be used is important. (b) Creating digital data sets by manual input The manual input of data to a GIS involves four main stages : • Entering the spatial data. • Entering the attribute data. • Spatial and attribute data verification and editing. • Where necessary, linking the spatial to the attribute data.

The manual data input methods depend on whether the database has a vector topology or grid cell (raster) structure. The most common ways of inputting data in to a GIS are through: • Digitisers • Scanners With the entity model, geographical data are in the form of points, lines and/ or polygons (areas)/pixels which are defined using a series of coordinates. These are obtained by referring to the geographical referencing systems of the map or aerial photograph, or by overlaying a graticule or grid onto it. The use of digitisers and the scanners greatly reduce the time and labour involved in writing down coordinates. We shall, briefly, discuss how the spatial data are created in GIS core using a scanner. Scanners

Entering the Attribute Data Attribute data define the properties of a spatial entity that need to be handled in the GIS, but which are not spatial. For example, a road may be captured as a set of contiguous pixels or as a line entity and represented in the spatial part of the GIS by a certain colour, symbol or data location. Information describing the type of road may be included in the range of cartographic symbols. The attribute values associated with the road, such as road width, type of surface, estimated number of traffic and specific traffic regulation may also be stored separately

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The scanners are the devices for converting analogue data into digital grid-based images. They are used in spatial data capture to convert a line map to highresolution raster images which may be used directly or further processed to get vector topology. There are two basic types of scanners : • Scanners that record data on a step-for -step basis, and • Those that can scan whole document in one operation. The first type of scanners incorporates a source of illumination on a movable arm (usually light emitting diodes or a stabilised fluorescent lamp) and a digital camera with high-resolution lamp. The camera is usually equipped with special sensors called Charged Coupled Devices (CCDs) arranged in an array. These are semi-conductor devices that translate the photons of light falling on their surface into counts of electrons, which are then recorded as a digital value. The movement of either the scanner or the map builds up a digital twodimensional image of the map. The map to be scanned can be mounted either on a flat bed, or on a rotating drum. With flatbed scanners, the light source is moved systematically up and down over the surface of the document. For large maps, scanners are used which are mounted on a stand and the illumination source and camera array are fixed in a position. The map is moved past by a feeding mechanism. Modern document scanners resemble laser printers in reverse because the scanning surface is manufactured with a given resolution of light sensitive spots that can be directly addressed by the software. There are no moving parts except a movable light source. The resolution is determined by the geometry of the sensor surface and the amount of memory rather than by a mechanical arm. The scanned image is always far from perfect even with the best possible scanners, as it contains all the smudges and defects of the original map. The excess data, therefore, in a digital image must be removed to make it usable.

either as spatial information in the GIS in case of relational databases, or input along with spatial description with the object-oriented data bases. The attribute data acquired from sources like published record, official censuses, primary surveys or spread sheets can be used as input into GIS database either manually or by importing the data using a standard transfer format. Data Verification and Editing The spatial data captured into a GIS require verification for the error identification and corrections so as to ensure the data accuracy. The errors caused during digitisation may include data omissions, and under/over shoots. The best way to check for errors in the spatial data is to produce a computer plot or print of the data, preferably on translucent sheet, at the same scale as the original. The two maps may then be placed over each other on a light table and compared visually, working systematically from left to right and top to bottom of the map. Missing data and locational errors should be clearly marked on the printout. The errors that may arise during the capturing of spatial and attribute data may be grouped as under : Spatial data are incomplete or double The incompleteness in the spatial data arises through omissions in the input of points, lines, or polygons/area of manually entered data. In scanned data the omissions are usually in the form of gaps between lines where the raster vector conversion process has failed to join up all parts of a line. Spatial data at the wrong scale

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The digitising at the wrong scale produces input spatial data at a wrong scale. In scanned data, the problems usually arise during the geo-referencing process when incorrect values are used. Spatial data are distorted The spatial data may also be distorted if the base maps used for digitising are not scale correct. The aerial photographs, in particular, are characterised by incorrect scale because of the lens distortions, relief and till displacements. In addition, paper maps and field documents used for scanning or digitising may contain random distortions as a result of having been exposed to rain, sunshine and frequent folding. Hence, transformation from one coordinate system to another may be needed if the coordinate system of the database is different from that used in the input document or image. These errors need corrections through various editing and updating functions as supported directly by most GIS. The process is time-consuming and interactive that can take longer time than the data input itself. The data editing is usually undertaken by viewing the portion of map containing the errors on the computer screen and correcting them through the software using the keyboard, screen cursor controlled by a mouse or a small digitiser tablet. Minor locational errors in a vector database may be corrected by moving the spatial entity through the screen cursor. In some GIS, computer commands may be used directly to move, rotate, erase, insert, stretch or truncate the graphical entities are required. Where excess coordinates define a line these may be removed using ‘weeding’ algorithms. Attribute values and spatial errors in raster data

must be corrected by changing the value of the faulty cells. Once, the spatial errors have been corrected, the topology of vector line and polygon networks can be generated. Data Conversion While manipulating and analysing data, the same format should be used for all data. When different layers are to be used simultaneously, they should all be in vector or all in raster format. Usually, the conversion is from vector to raster, because the biggest part of the analysis is done in the raster domain. Vector data are transformed to raster data by overlaying a grid with a user-defined cell size. Sometimes, the data in the raster format are converted into vector format. This is the case especially if one wants to achieve data reduction because the data storage needed for raster data are much larger than for vector data. Geographic Data : Linkages and Matching The linkages of spatial and the attribute data are important in GIS. It must, therefore, carefully be undertaken. Linking of attribute data with a non-related spatial data shall lead to chaos in ultimate data analysis. Similarly, matching of one data layer with another is also significant. Linkages A GIS typically links different data sets. Suppose, we want to know the mortality rate due to malnutrition among children under 10 years of age in any state. If we have one file that contains the number of children in this age group, and another that contains the mortality rate from malnutrition, we must first combine or link the two data files. Once this is done, we can divide one figure by the other to obtain the desired answer. Exact Matching

Hierarchical Matching Some types of information, however, are collected in more detail and less frequently than other types of information. For example, land use data covering a large area are collected quite frequently. On the other hand, land transformation data are collected in small areas but at less frequent intervals. If the smaller areas adjust within the larger ones, then the way to make the data match of the same area is to use hierarchical matching — add the data for the small areas together until the grouped areas match the bigger ones and then match them exactly. Fuzzy Matching On many occasions, the boundaries of the smaller areas do not match with those of the larger ones. The problem occurs more often when the environmental data are involved. For example, crop boundaries that are usually defined by field edges/boundaries rarely match with the boundaries of the soil types. If we want

Technology Spatial Information T echnology

Exact matching means when we have information in one computer file about many geographic features (e.g., towns) and additional information in another file about the same set of features. The operation to bring them together may easily be achieved using a key common to both files, i. e. name of the towns. Thus, the record in each file with the same town name is extracted, and the two are joined and stored in another file.

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to determine the most productive soil for a particular crop, we need to overlay the two sets and compute crop productivity for each soil type. This is like laying one map over another and noting the combinations of soil and productivity. A GIS can carry out all these operations. However, the sets of spatial information are linked only when they relate to the same geographical area. Spatial Analysis The strength of the GIS lies in its analytical capabilities. What distinguish the GIS from other information systems are its spatial analysis functions. The analysis functions use the spatial and non-spatial attributes in the database to answer questions about the real world. Geographic analysis facilitates the study of realworld processes by developing and applying models. Such models provide the underlying trends in geographic data and thus, make new possibilities available. The objective of geographic analysis is to transform data into useful information to satisfy the requirements of the decision-makers. For example, GIS may effectively be used to predict future trends over space and time related to variety of phenomena. However, before undertaking any GIS based analysis, one needs to identify the problem and define purpose of the analysis. It requires step – by – step procedures to arrive at the conclusions. The following spatial analysis operation may be undertaken using GIS : (i) Overlay (ii) Buffer analysis (iii) Network analysis (iv) Digital Terrain Model However, under the constraints of time and space only the overlay and buffer analysis operations will be dealt herewith. Overlay Operations

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The hallmark of GIS is overlay operations. An integration of multiple layers of maps using overlay operations is an important analysis function. In other words, GIS makes it possible to overlay two or more thematic layers of maps of the same area to obtain a new map layer (Fig. 6.7). The overlay operations of a GIS are Overlay Operation : x + y = z where x = Road map y = Rail map z = Communication Map + = The spatial overlay operation ‘union’ Graphical representation Road map

+ Rail map

= Communication map

Fig. 6.7 : Simple Overlay Operation

Fig. 6.8 : Urban Land Use in Aligarh City, Uttar Pradesh during 1974 and 2001

97 Technology Spatial Information T echnology

Fig. 6.9 : Urban Land Transformations in Aligarh City during 1974-2001

similar to the sieve mapping, i. e. the overlaying of tracing of maps on a light table to make comparisons and obtain an output map. Map overlay has many applications. It can be used to study the changes in land use/land cover over two different periods in time and analyse the land transformations. For example, Fig. 6.8 depicts urban land use during 1974 and 2001. When the two maps overlaid, the changes in urban land use have been obtained (Fig. 6.9) and the urban sprawl is mapped during the given time period (Fig. 6.10). Similarly, overlay analysis is also useful in suitability analysis of the given land use for proposed land uses.

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Fig. 6.10 : Urban Sprawl of Aligarh City, Uttar Pradesh during 1974-2001

Buffer Operation Buffer operation is another important spatial analysis function in GIS. A buffer of a certain specified distance can be created along any point, line or area feature (Fig. 6.11). It is useful in locating the areas/population benefitted or denied of the facilities and services such as hospitals, medical stores, post office, asphalt roads, regional parks, etc. Similarly, it can also be used to study the impact of point sources of air, noise or water pollution on human health and the size of the population so affected. This kind of analysis is called proximity analysis. The buffer operation will generate polygon feature types irrespective of geographic features and delineates spatial proximity. For example, numbers of household living within one-kilometre buffer from a chemical industrial unit are affected by industrial waste discharged from the unit. Arc View/ArcGIS, Geomedia and all other GIS software provide modules for buffer analysis along point, line and area features. For example, using appropriate commands of either of the available software one can create buffers of 2, 4, 6, 8, and 10 kilometres around the cities having a major hospital located therein. As a case study, point location of Saharanpur, Muzaffarnagar, Meerut, Ghaziabad,

Fig. 6.11 : Buffers of Constant Width Drawn around a Point, Line and a Polygon

Fig. 6.12 : Location Map of the Cities of Western Uttar Pradesh

Fig. 6.13 : Buffers of Specified Distances around Hospitals

99 Technology Spatial Information T echnology

Gautam Budh Nagar and Aligarh has been mapped (Fig. 6.12) and the buffer have been created from the cities where major hospitals are found. One can observe that the areas closer to the cities are better served, people living away from the cities have to travel long distances to utilise the medical services and their areas that are least benefitted (Fig. 6.13).

Excercises 1. Choose the right answer from the four alternatives given below : (i) The spatial data are characterised by the following forms of appearance : (a) Positional (b) Linear (c) Areal (d) All the above forms (ii) Which one of the following operations requires analysis module software? (a) Data storage (b) Data display (c) Data output (d) Buffering (iii) Which one of the following is disadvantage of Raster data format ? (a) Simple data structure (b) Easy and efficient overlaying (c) Compatible with remote sensing imagery (d) Difficult network analysis (iv) Which one of the following is an advantage of Vector data format ? (a) Complex data structure (b) Difficult overlay operations (c) Lack of compatibility with remote sensing data (d) Compact data structure (v) Urban change detection is effectively undertaken in GIS core using: (a) Overlay operations (b) Proximity analysis (c) Network analysis (d) Buffering 2. Answer the following questions in about 30 words : (i) Differentiate between raster and vector data models.

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100

(ii) What is an overlay analysis? (iii) What are the advantages of GIS over manual methods? (iv) What are important components of GIS? (v) What are different ways in which spatial data is built in GIS core? (vi) What is Spatial Information Technology? 3. Answer the following questions in about 125 words : (i) Discuss raster and vector data formats. Give example. (ii) Write an explanatory account of the sequence of activities involved in GIS related work.

Contents FOREWORD UNIT I 1.

Human Geography Nature and Scope

UNIT II 2.

iii

1-7 1

8-30

The World Population Distribution, Density and Growth

8

3.

Population Composition

17

4.

Human Development

22

UNIT III

31-90

5.

Primary Activities

31

6.

Secondary Activities

45

7.

Tertiary and Quaternary Activities

55

8.

Transport and Communication

65

9.

International Trade

81

UNIT IV 10.

Human Settlements

91-102 90

APPENDIX I

103

APPENDIX II

107

GLOSSARY

110

Unit-I Chapter-1

Human Geography Nature and Scope

You have already studied ‘Geography as a Discipline’ in Chapter I of the book, Fundamentals of Physical Geography (NCERT, 2006). Do you recall the contents? This chapter has broadly covered and introduced you to the nature of geography. You are also acquainted with the important branches that sprout from the body of geography. If you re-read the chapter you will be able to recall the link of human geography with the mother discipline i.e. geography. As you know geography as a field of study is integrative, empirical, and practical. Thus, the reach of geography is extensive and each and every event or phenomenon which varies over space and time can be studied geographically. How do you see the earth’s surface? Do you realise that the earth comprises two major components: nature (physical environment) and life forms including human beings? Make a list of physical and human components of your surroundings. Physical geography studies physical environment and human geography studies “the relationship between the physical/natural and the human worlds, the spatial distributions of human phenomena and how they come about, the social and economic differences between different parts of the world”.1 You are already aware of the fact that the core concern of geography as a discipline is to understand the earth as home of human beings and to study all those elements which have sustained them. Thus, emphasis is on study of nature and human beings. You will realise that geography got subjected to dualism and the wide-ranging debates started whether geography as a discipline should be a law making/theorising (nomothetic) or descriptive (idiographic). Whether its subject matter should be organised and approach of the study should be regional or systematic? Whether geographical phenomena be interpreted theoretically or through historicinstitutional approach? These have been issues for intellectual exercise but finally you will appreciate that the dichotomy between physical and human is not a very valid one because nature and human are inseparable elements and should be seen holistically. It is interesting to note that both physical and human 1

Agnew J. Livingstone, David N. and Rogers, A.; (1996) Blackwell Publishing Limited, Malden, U.S.A. p. 1 and 2.

phenomena are described in metaphors using symbols from the human anatomy. We often talk of the ‘face’ of the earth, ‘eye’ of the storm, ‘mouth’ of the river, ‘snout’ (nose) of the glacier, ‘neck’ of the isthmus and ‘profile’ of the soil. Similarly regions, villages, towns have been described as ‘organisms’. German geographers describe the ‘state/country’ as a ‘living organism’. Networks of road, railways and water ways have often been described as “arteries of circulation”. Can you collect such terms and expressions from your own language? The basic questions now arises, can we separate nature and human when they are so intricately intertwined?

Human Geography Defined • “Human geography is the synthetic study of relationship between human societies and earth’s surface”. Ratzel Synthesis has been emphasised in the above definition. • “Human geography is the study of “the changing relationship between the unresting man and the unstable earth.” Ellen C. Semple Dynamism in the relationship is the keyword in Semple’s definition. • “Conception resulting from a more synthetic knowledge of thephysical laws governing our earth and of the relations between the living beings which inhabit it”. Paul Vidal de la Blache Human geography offers a new conception of the interrelationships between earth and human beings.

NATURE OF HUMAN GEOGRAPHY Human geography studies the inter-relationship between the physical environment and sociocultural environment created by human beings through mutual interaction with each other. You 2

Fundamentals of Human Geography

have already studied the elements of physical environment in class XI in the book entitled Fundamentals of Physical Geography (NCERT 2006). You know that these elements are landforms, soils, climate, water, natural vegetation and diverse flora and fauna. Can you make a list of elements which human beings have created through their activities on the stage provided by the physical environment? Houses, villages, cities, road-rail networks, industries, farms, ports, items of our daily use and all other elements of material culture have been created by human beings using the resources provided by the physical environment. While physical environment has been greatly modified by human beings, it has also, in turn, impacted human lives. Naturalisation of Humans and Humanisation of Nature Human beings interact with their physical environment with the help of technology. It is not important what human beings produce and create but it is extremely important ‘with the help of what tools and techniques do they produce and create’. Technology indicates the level of cultural development of society. Human beings were able to develop technology after they developed better understanding of natural laws. For example, the understanding of concepts of friction and heat helped us discover fire. Similarly, understanding of the secrets of DNA and genetics enabled us to conquer many diseases. We use the laws of aerodynamics to develop faster planes. You can see that knowledge about Nature is extremely important to develop technology and technology loosens the shackles of environment on human beings. In the early stages of their interaction with their natural environment humans were greatly influenced by it. They adapted to the dictates of Nature. This is so because the level of technology was very low and the stage of human social development was also primitive. This type of interaction between primitive human society and strong forces of nature was termed as environmental determinism. At that stage of very low technological development we can imagine the presence of a naturalised human, who listened to Nature, was afraid of its fury and worshipped it.

The Naturalisation of Humans Benda lives in the wilds of the Abujh Maad area of central India. His village consists of three huts deep in the wilds. Not even birds or stray dogs that usually crowd villages can be seen in these areas. Wearing a small loin cloth and armed with his axe he slowly surveys the penda (forest) where his tribe practices a primitive form of agriculture called shifting cultivation. Benda and his friends burn small patches of forest to clear them for cultivation. The ash is used for making the soil fertile. Benda is happy that the Mahua trees around him are in bloom. How lucky I am to be a part of this beautiful universe, he thinks as he looks up to see the Mahua, Palash and Sal trees that have sheltered him since childhood. Crossing the penda in a gliding motion, Benda makes his way to a stream. As he bends down to scoop up a palmful of water, he remembers to thank Loi-Lugi, the spirit of the forest for allowing him to quench his thirst. Moving on with his friends, Benda chews on succulent leaves and roots. The boys have been trying to collect Gajjhara and Kuchla, from the forest. These are special plants that Benda and his people use. He hopes the spirits of the forest will be kind and lead him to these herbs. These are needed to barter in the madhai or tribal fair coming up the next full moon. He closes his eyes and tries hard to recall what the elders had taught him about these herbs and the places they are found in. He wishes he had listened more carefully. Suddenly there is a rustling of leaves. Benda and his friends know it is the outsiders who have come searching for them in the wilds. In a single fluid motion Benda and his friends disappear behind the thick canopy of trees and become one with the spirit of the forest.

The story in the box represents the direct relationship of a household belonging to an economically primitive society with nature. Read about other primitive societies which live in complete harmony with their natural environment. You will realise that in all such cases nature is a powerful force, worshipped, revered and conserved. There is direct dependence of

human beings on nature for resources which sustain them. The physical environment for such societies becomes the “Mother Nature”. The people begin to understand their environment and the forces of nature with the passage of time. With social and cultural development, humans develop better and more efficient technology. They move from a state of necessity to a state of freedom. They create possibilities with the resources obtained from the environment. The human activities create cultural landscape. The imprints of human activities are created everywhere; health resorts on highlands, huge urban sprawls, fields, orchards and pastures in plains and rolling hills, ports on the coasts, oceanic routes on the oceanic surface and satellites in the space. The earlier scholars termed this as possibilism. Nature provides opportunities and human being make use of these and slowly nature gets humanised and starts bearing the imprints of human endeavour.

Humanisation of Nature Winters in the town of Trondheim mean fierce winds and heavy snow. The skies are dark for months. Kari drives to work in the dark at 8 am. She has special tyres for the winter and keeps the headlights of her powerful car switched on. Her office is artificially heated at a comfortable 23 degrees Celsius. The campus of the university she works in is built under a huge glass dome. This dome keeps the snow out in winter and lets in the sunshine in the summer. The temperature is controlled carefully and there is adequate lighting. Even though fresh vegetables and plants don’t grow in such harsh weather, Kari keeps an orchid on her desk and enjoys eating tropical fruits like banana and kiwi. These are flown in from warmer areas regularly. With a click of the mouse, Kari can network with colleagues in New Delhi. She frequently takes a morning flight to London and returns in the evening in time to watch her favourite television serial. Though Kari is fifty-eight years old, she is fitter and looks younger than many thirtyyear- olds in other parts of the world.

Human Geography: Nature and Scope

3

Can you imagine what has made such a life style possible? It is technology that has allowed the people of Trondheim and others to overcome the constraints imposed by nature. Do you know about some other such instances? Such examples are not difficult to find. A geographer, Griffith Taylor introduced another concept which reflects a middle path (Madhyam Marg) between the two ideas of environmental determinism and possibilism. He termed it as Neodeterminism or stop and go determinism. Those of you who live in cities and those who have visited a city, might have seen that traffic is regulated by lights on the cross-roads. Red light means ‘stop’, amber light provides a gap between red and green lights ‘to get set’ and green light means ‘go’. The concept shows that neither is there a situation of absolute necessity (environmental determinism) nor is there a condition of absolute freedom (possibilism). It means that human beings can conquer nature by obeying it. They have to respond to the red signals and can proceed in their pursuits of development when nature permits the modifications. It means that possibilities can be created within the limits which do not damage the environment and there is no free run without accidents. The free run which the developed economies attempted to take has already resulted in the green house effect, ozone layer depletion, global warming, receding glaciers and degrading lands. The neo-determinism conceptually attempts to bring a balance nullifying the ‘either’ ‘or’ dichotomy. Human Geography through the Corridors of Time The process of adaptation, adjustment with and modification of the environment started with the appearance of human beings over the surface of the earth in different ecological niches. Thus, if we imagine the beginning of human geography with the interaction of environment and human beings, it has its roots deep in history. Thus, the concerns of human geography have a long temporal continuum though the approaches to articulate them have changed over time. This dynamism in 4

Fundamentals of Human Geography

approaches and thrusts shows the vibrant nature of the discipline. Earlier there was little interaction between different societies and the knowledge about each other was limited. Travellers and explorers used to disseminate information about the areas of their visits. Navigational skills were not developed and voyages were fraught with dangers. The late fifteenth century witnessed attempts of explorations in Europe and slowly the myths and mysteries about countries and people started to open up. The colonial period provided impetus to further explorations in order to access the resources of the regions and to obtain inventorised information. The intention here is not to present an in-depth historical account but to make you aware of the processes of steady development of human geography. The summarised Table 1.1 will introduce you to the broad stages and the thrust of human geography as a sub-field of geography. • Welfare or humanistic school of thought in human geography was mainly concerned with the different aspects of social well-being of the people. These included aspects such as housing, health and education. Geographers have already introduced a paper as Geography of Social well-being in the Post Graduate curriculum’. • Radical school of thought employed Marxian theory to explain the basic cause of poverty, deprivation and social inequality. Contemporary social problems were related to the development of capitalism. • Behavioural school of thought laid great emphasis on lived experience and also on the perception of space by social categories based on ethnicity, race and religion, etc.

Fields and Sub-fields of Human Geography Human geography, as you have seen, attempts to explain the relationship between all elements of human life and the space they occur over. Thus, human geography assumes a highly inter-disciplinary nature. It develops close

Table 1.1: Broad Stages and Thrust of Human Geography

Period

Approaches

Broad Features

Colonial period

Exploration and description

Imperial and trade interests prompted the discovery and exploration of new areas. An encyclopaedic description of the area formed an important aspect of the geographer’s account.

Colonial period

Regional analysis

Elaborate description of all aspects of a region were undertaken. The idea was that all the regions were part of a whole, ie (the earth); so, understanding the parts in totality would lead to an understanding of the whole.

1930s through the inter-War period

Areal differentiation

The focus was on identifying the uniqueness of any region and understanding how and why it was different from others.

Late 1950s to the late 1960s

Spatial organisation

Marked by the use of computers and sophisticated statistical tools. Laws of physics were often applied to map and analyse human phenomena. This phase was called the quantitative revolution. The main objective was to identify mappable patterns for different human activities.

1970s

Emergence of humanistic, radical and behavioural schools

Discontentment with the quantitative revolution and its dehumanised manner of doing geography led to the emergence of three new schools of thought of human geography in the 1970s. Human geography was made more relevant to the socio-political reality by the emergence of these schools of thought. Consult the box below to know a little bit more about these schools of thought.

1990s

Post-modernism in geography

The grand generalisations and the applicability of universal theories to explain the human conditions were questioned. The importance of understanding each local context in its own right was emphasised.

interface with other sister disciplines in social sciences in order to understand and explain human elements on the surface of the earth. With the expansion of knowledge, new subfields emerge and it has also happened to human geography. Let us examine these fields and sub-fields of Human Geography (Table 1.2). You would have noticed that the list is large and comprehensive. It reflects the

expanding realm of human geography. The boundaries between sub-fields often overlap. What follows in this book in the form of chapters will provide you a fairly widespread coverage of different aspects of human geography. The exercises, the activities and the case studies will provide you with some empirical instances so as to have a batter understanding of its subject matter.

Human Geography: Nature and Scope

5

Table 1.2: Human Geography and Sister Disciplines of Social Sciences

Fields of Human Geography

Sub-fields

Social

—

Geography

Interface with Sister Disciplines of Social Sciences Social Sciences – Sociology

Behavioural Geography

Psychology

Geography of Social

Welfare Economics

Well-being Geography of Leisure

Sociology

Cultural Geography

Anthropology

Gender Geography

Sociology, Anthropology, Women’s Studies

Historical Geography

History

Medical Geography

Epidemology

Urban

—

Urban Studies and Planning

—

Political Science

Geography Political Geography

Electoral Geography Military Geography

Population

Psephology Military Science

—

Demography

—

Urban/Rural Planning

Geography Settlement Geography Economic

—

Geography

Economics

Geography of Resources

Resource Economics

Geography of Agriculture

Agricultural Sciences

Geography of Industries

Industrial Economics

Geography of Marketing

Business Studies, Economics, Commerce

Geography of Tourism

Tourism and Travel Management

Geography of International

International Trade

Trade

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i) Which one of the following statements does not describe geography? (a) an integrative discipline (b)

6

study of the inter-relationship between humans and environment

Fundamentals of Human Geography

(ii)

(c)

subjected to dualism

(d)

not relevant in the present time due to the development of technology.

Which one of the following is not a source of geographical information? (a)

(iii)

(iv)

(b)

old maps

(c)

samples of rock materials from the moon

(d)

ancient epics

Which one of the following is the most important factor in the interaction between people and environment? (a)

human intelligence

(c)

technology

(b)

people’s perception

(d)

human brotherhood

Which one of the following is not an approach in human geography? (a)

2.

traveller’s accounts

Areal differentiation

(c)

Quantitative revolution

(b) Spatial organisation (d) Exploration and description Answer the following questions in about 30 words. (i) Define human geography. (ii)

Name some sub-fields of human geography.

How is human geography related to other social sciences? (iii) 3. Answer the following questions in not more than 150 words. (i) Explain naturalisation of humans. (ii)

Write a note on the scope of human geography.

Human Geography: Nature and Scope

7

Unit-IV Chapter-10

Human Settlements

We all live in clusters of houses. You may call it a village, a town or a city, all are examples of human settlements. The study of human settlements is basic to human geography because the form of settlement in any particular region reflects human relationship with the environment. A human settlement is defined as a place inhabited more or less permanently. The houses may be designed or redesigned, buildings may be altered, functions may change but settlement continues in time and space. There may be some settlements which are temporary and are occupied for short periods, may be a season.

CLASSIFICATION OF SETTLEMENTS RURAL URBAN DICHOTOMY It is widely accepted that settlements can be differentiated in terms of rural and urban, but there is no consensus on what exactly defines a village or a town. Although population size is an important criterion, it is not a universal criterion since many villages in densely populated countries of India and China have population exceeding that of some towns of Western Europe and United States. At one time, people living in villages pursued agriculture or other primary activities, but presently in developed countries, large sections of urban populations prefer to live in villages even though they work in the city. The basic difference between towns and villages is that in towns the main occupation of the people is related to secondary and tertiary sectors, while in the villages most of the people are engaged in primary occupations such as agriculture, fishing, lumbering, mining, animal husbandry, etc.

Sub Urbanisation It is a new trend of people moving away from congested urban areas to cleaner areas outside the city in search of a better quality of living. Important suburbs develop around major cities and everyday thousands of people commute from their homes in the sub urbs to their work places in the city.

Differentiations between rural and urban on the basis of functions are more meaningful even though there is no uniformity in the hierarchy of the functions provided by rural and urban settlements. Petrol pumps are considered as a lower order function in the United States while it is an urban function in India. Even within a country, rating of functions may vary according to the regional economy. Facilities available in the villages of developed countries may be considered rare in villages of developing and less developed countries. The census of India, 1991 defines urban settlements as “All places which have municipality, corporation, cantonment board or notified town area committee and have a minimum population of 5000 persons, at least 75 per cent of male workers are engaged in non-agricultural pursuits and a density of population of at least 400 persons per square kilometers are urban.

TYPES AND PATTERNS OF SETTLEMENTS Settlements may also be classified by their shape, patterns types. The major types classified by shape are: (i) Compact or Nucleated settlements: These settlements are those in which large number of houses are built very close to each other. Such settlements develop along river valleys and in fertile plains. Communities are closely knit and share common occupations.

(ii)

Dispersed Settlements: In these settlements, houses are spaced far apart and often interspersed with fields. A cultural feature such as a place of worship or a market, binds the settlement together.

Fig. 10.2: Dispersed Settlements

Rural Settlements Rural settlements are most closely and directly related to land. They are dominated by primary activities such as agriculture, animal husbandary, fishing etc. The settlements size is relatively small.

Fig. 10.3 : Siting near water

Water Supply

Fig.10.1 : Compact Settlements

92

Fundamentals of Human Geography

Usually rural settlements are located near water bodies such as rivers, lakes, and springs where water can be easily obtained. Sometimes the need for water drives people to settle in otherwise disadvantaged sites such as islands surrounded by swamps or low lying river banks. Most water based ‘wet point’ settlements have many advantages such as water for

drinking, cooking and washing. Rivers and lakes can be used to irrigate farm land. Water bodies also have fish which can be caught for diet and navigable rivers and lakes can be used for transportation. Land People choose to settle near fertile lands suitable for agriculture. In Europe villages grew up near rolling country avoiding swampy, low lying land while people in south east Asia chose to live near low lying river valleys and coastal plains suited for wet rice cultivation. Early settlers chose plain areas with fertile soils. Upland Upland which is not prone to flooding was chosen to prevent damage to houses and loss of life. Thus, in low lying river basins people chose to settle on terraces and levees which are “dry points”. In tropical countries people build their houses on stilts near marshy lands to protect themselves from flood, insects and animal pests. Building Material The availability of building materials- wood, stone near settlements is another advantage. Early villages were built in forest clearings where wood was plentiful.

Fig. 10.4 : House on stilts

In loess areas of China, cave dwellings were important and African Savanna’s building materials were mud bricks and the Eskimos, in polar regions, use ice blocks to construct igloos.

Defence During the times of political instability, war, hostility of neighbouring groups villages were built on defensive hills and islands. In Nigeria, upstanding inselbergs formed good defensive sites. In India most of the forts are located on higher grounds or hills. Planned Settlements Sites that are not spontaneously chosen by villagers themselves, planned settlements are constructed by governments by providing shelter, water and other infrastructures on acquired lands. The scheme of villagisation in Ethiopia and the canal colonies in Indira Gandhi canal command area in India are some good examples. Rural Settlement Patterns Patterns of rural settlements reflect the way the houses are sited in relation to each other. The site of the village, the surrounding topography and terrain influence the shape and size of a village. Rural settlements may be classified on the basis of a number of criteria: (i) On the basis of setting: The main types are plain villages, plateau villages, coastal villages, forest villages and desert villages. (ii) On the basis of functions: There may be farming villages, fishermen’s villages, lumberjack villages, pastoral villages etc. (iii) On the basis of forms or shapes of the settlements: These may be a number of geometrical forms and shapes such as Linear, rectangular, circular star like, T-shaped village, double village, cross-shaped village etc. (a) Linear pattern: In such settlements houses are located along a road, railway line, river, canal edge of a valley or along a levee. (b) Rectangular pattern: Such patterns of rural settlements are found in plain areas or wide inter montane valleys. The roads are rectangular and cut each other at right angles. Human Settlements

93

Linear Pattern

Cross-shape Pattern

Star-like Pattern

T-Shape Pattern

Circular Pattern

Double Pattern

Railway

Road

River

Canal

Well

Bridge

Temple

Village

Pond

Tree

Fig. 10.5: Rural Settlement Patterns

(c)

(d)

(e)

Circular pattern: Circular villages develop around lakes, tanks and sometimes the village is planned in such a way that the central part remains open and is used for keeping the animals to protect them from wild animals. Star like pattern: Where several roads converge, star shaped settlements develop by the houses built along the roads. T-shaped, Y-shaped, Cross-shaped or crucifor m settlements: T -shaped

Fig.10.6 : Linear pattern settlement

94

Fundamentals of Human Geography

settlements develop at tri-junctions of ) while -shaped the roads ( settlements emerge as the places where two roads converge on the third one and houses are built along these roads. Cruciform settlements develop on the cross-roads and houses extend in all the four direction.

Fig.10.7 : Y shape settlement

(f)

Double village: These settlements extend on both sides of a river where there is a bridge or a ferry.

Identify these patterns on any topographical sheet which you have studied in Practical Work in Geography, Part I (NCERT, 2006) in Class XI

Problems of Rural Settlements Rural settlements in the developing countries are large in number and poorly equipped with infrastructure. They represent a great challenge and opportunity for planners. Supply of water to rural settlements in developing countries is not adequate. People in villages, particularly in mountainous and arid areas have to walk long distances to fetch drinking water. Water borne diseases such as cholera and jaundice tend to be a common problem. The countries of South Asia face conditions of drought and flood very often. Crop cultivation sequences, in the absence of irrigation, also suffer. The general absence of toilet and garbage disposal facilities cause health related problems. The design and use of building materials of houses vary from one ecological region to another. The houses made up of mud, wood and thatch, remain susceptible to damage during heavy rains and floods, and require proper maintenance every year. Most house designs are typically deficient in proper ventilation. Besides, the design of a house includes the animal shed along with its fodderstore within it. This is purposely done to keep the domestic animals and their food properly protected from wild animals. Unmetalled roads and lack of modern communication network creates a unique problem. During rainy season, the settlements remain cut off and pose serious difficulties in providing emergency services. It is also difficult to provide adequate health and educational infrastructure for their large rural population. The problem is particularly serious where proper villagisation has not taken place and houses are scattered over a large area.

Urban Settlements Rapid urban growth is a recent phenomenon. Until recent times, few settlements reached the population size of more than a few thousand inhabitants. The first urban settlement to reach a population of one million was the city of London by around. A.D. 1810 By 1982 approximately 175 cities in the world had crossed the one million population mark. Presently 48 per cent of the world’s population lives in urban settlements compared to only 3 per cent in the year 1800 (Table 10.1). Table 10.1: Percentage of World’s Population Living in Urban Areas

Year

Percentage

1800

3

1850

6

1900

14

1950

30

1982

37

2001

48

Classification of Urban Settlements The definition of urban areas varies from one country to another. Some of the common basis of classification are size of population, occupational structure and administrative setup. Population Size It is an important criteria used by most countries to define urban areas. The lower limit of the population size for a settlement to be designated as urban is 1,500 in Colombia, 2,000 in Argentina and Portugal, 2,500 in U.S.A. and Thailand, 5,000 in India and 30,000 in Japan. Besides the size of population, density of 400 persons per sq km and share of non-agricultural workers are taken into consideration in India. Countries with low density of population may choose a lower number as the cut-off figure compared to densely populated countries. In Denmark, Sweden and Finland, all places with a population size of 250 persons are called urban. The minimum population for a city is Human Settlements

95

300 in Iceland, whereas in Canada and Venezuela, it is 1,000 persons.

urban centres which are located close to an important trade route have experienced rapid development.

Occupational Structure In some countries, such as India, the major economic activities in addition to the size of the population in designating a settlement as urban are also taken as a criterion. Similarly, in Italy, a settlement is called urban, if more than 50 per cent of its economically productive population is engaged in non-agricultural pursuits. India has set this criterion at 75 per cent. Administration The administrative setup is a criterion for classifying a settlement as urban in some countries. For example, in India, a settlement of any size is classified as urban, if it has a municipality, Cantonment Board or Notified Area Council. Similarly, in Latin American countries, such as Brazil and Bolivia, any administrative centre is considered urban irrespective of its population size.

Functions of Urban Centres The earliest towns were centres of administration, trade, industry, defence and religious importance. The significance of defence and religion as differentiating functions has declined in general, but other functions have entered the list. Today, several new functions, such as, recreational, residential, transport, mining, manufacturing and most recently activities related to information technology are carried on in specialised towns. Some of these functions do not necessarily require the urban centre to have any fundamental relationship with their neighbouring rural areas.

What would be the effects of Information and Communication Technology (ICT) as a function on the development of existing and new settlements?

Location Location of urban centres is examined with reference to their function. For example, the sitting requirements of a holiday resort are quite different from that of an industrial town, a military centre or a seaport. Strategic towns require sites offering natural defence; mining towns require the presence of economically valuable minerals; industrial towns generally need local energy supplies or raw materials; tourist centres require attractive scenery, or a marine beach, a spring with medicinal water or historical relics, ports require a harbour etc. Locations of the earliest urban settlements were based on the availability of water, building materials and fertile land. Today, while these considerations still remain valid, modern technology plays a significant role in locating urban settlements far away from the source of these materials. Piped water can be supplied to a distant settlement, building material can be transported from long distances. Apart from site, the situation plays an important role in the expansion of towns. The 96

Fundamentals of Human Geography

Prepare a list of cities where earlier functions have been replaced by newer ones.

In spite of towns performing multiple functions we refer to their dominant function. For example, we think of Sheffield as an industrial city, London as a port city, Chandigarh as an administrative city and so on. Large cities have a rather greater diversity of functions. Besides, all cities are dynamic and over a period of time may develop new functions. Most of the early nineteenth-century fishing ports in England have now developed tourism. Many of the old market towns are now known for manufacturing activities. Towns and cities are classified into the following categories. Administrative Towns National capitals, which house the administrative offices of central governments, such as New Delhi, Canberra, Beijing, Addis Ababa, Washington D.C., and London etc. are called administrative

towns. Provincial (sub-national) towns can also have administrative functions, for example, Victoria (British Columbia), Albany (New York), Chennai (Tamil Nadu). Trading and Commercial Towns Agricultural market towns, such as, Winnipeg and Kansas city; banking and financial centres like Frankfurt and Amsterdam; large inland centres like Manchester and St Louis; and transport nodes such as, Lahore, Baghdad and Agra have been important trading centres. Cultural Towns Places of pilgrimage, such as Jerusalem, Mecca, Jagannath Puri and Varanasi etc. are considered cultural towns. These urban centres are of great religious importance. Additional functions which the cities perform are health and recreation (Miami and Panaji), industrial (Pittsburgh and Jamshedpur), mining and quarrying (Broken Hill and Dhanbad) and transport (Singapore and Mughal Sarai).

Towns and cities of developed and developing countries reflect marked differences in planning and development. While most cities in developed countries are planned, most urban settlements of developing countries have evolved historically with irregular shapes. For example, Chandigarh and Canberra are planned cities, while smaller town in India have evolved historically from walled cities to large urban sprawls. Addis Ababa (The New Flower) The name of Ethiopian capital Addis Ababa, as the name indicates (Addis-New, Ababa-Flower) is a ‘new’ city which was established in 1878. The whole city is located on a hill-valley topography. The road pattern bears the influence

Urbanisation means the increase in the proportion population of a country who live in urban areas. The most important cause of urbanisation is rural-urban migration. During the late 1990s some 20 to 30 million people were leaving the countryside every year and moving into towns and cities. Developed countries experienced rapid urbanisation during the nineteenth century.

Fig. 10.8: Morphology of Addis Ababa

Developing counties experienced rapid urbanisation during the second half of the twentieth century.

CLASSIFICATION OF TOWNS ON THE BASIS OF FORMS An urban settlement may be linear, square, star or crescent shaped. In fact, the form of the settlement, architecture and style of buildings and other structures are an outcome of its historical and cultural traditions. Fig. 10.9: Skyline of Addis Ababa

Human Settlements

97

of the local topography. The roads radiate from the govt headquarters Piazza, Arat and Amist Kilo roundabouts. Mercato has markets which grew with time and is supposed to be the largest market between Cairo and Johannesburg. A multi-faculty university, a medical college, a number of good schools make Addis Ababa an educational centre. It is also the terminal station for the Djibouti-Addis Ababa rail route. Bole airport is a relatively new airport. The city has witnessed rapid growth because of its multifunctional nature and being a large nodal centre located in the centre of Ethiopia.

each with separate city functions. During the last few decades, the city has expanded to accommodate several satellite towns, which have their own centres. The city has wide-open spaces and many parks and gardens.

Canberra

The concept of ‘town’ can best be understood with reference to ‘village’. Population size is not the only criterion. Functional contrasts between towns and villages may not always be clearcut, but specific functions such as, manufacturing, retail and wholesale trade, and professional services exist in towns.

Canberra was planned as the capital of Australia in 1912 by American landscape architect, Walter Burley Griffin. He had envisaged a garden city for about 25,000 people taking into account the natural features of the landscape. There were to be five main centres,

Types of Urban Settlements Depending on the size and the services available and functions rendered, urban centres are designated as town, city, million city, conurbation, megalopolis. Town

City A city may be regarded as a leading town, which has outstripped its local or regional rivals. In the words of Lewis Mumford, “ the city is in fact the physical form of the highest and most complex type of associative life”. Cities are much larger than towns and have a greater number of economic functions. They tend to have transport terminals, major financial institutions and regional administrative offices. When the population crosses the one million mark it is designated as a million city. Conurbation The term conurbation was coined by Patrick Geddes in 1915 and applied to a large area of urban development that resulted from the merging of originally separate towns or cities. Greater London, Manchester, Chicago and Tokyo are examples. Can you find out an example from India? Megalopolis

Fig. 10.10 : Morphology of a planned city – Canberra

98

Fundamentals of Human Geography

This Greek word meaning “great city”, was popularised by Jean Gottman (1957) and signifies ‘super- metropolitan’ region extending,

as union of conurbations. The urban landscape stretching from Boston in the north to south of Washington in U.S.A. is the best known example of a megalopolis. Million City The number of million cities in the world has been increasing as never before. London reached the million mark in 1800, followed by Paris in 1850, New York in 1860, and by 1950 there were around 80 such cities. The rate of increase in the number of million cities has been three-fold in every three decades – around 160 in 1975 to around 438 in 2005. Table 10.2: Continent–wise Distribution of Million Cities

Continent

Early 1950

Mid 1970s

Europe

23

30

58

Asia

32

69

206

North and Central America

16

36

79

South America

8

17

43

Africa

3

8

46

Australia

2

2

6

84

162

438

World Total

Mid 2000

Source: www.citypopulation.de/World.html

Distribution of Mega Cities A mega city or megalopolis is a general term for cities together with their suburbs with a population of more than 10 million people. New York was the first to attain the status of a mega city by 1950 with a total population of about 12.5 million. The number of mega cities is now 25. The number of mega cities has increased in the developing countries during the last 50 years vis-à-vis the developed countries. Problems of Human Settlements in Developing Countries The settlements in developing countries, suffer from various problems, such as unsustainable concentration of population, congested housing and streets, lack of drinking water facilities.

Table 10.3: Mega Cities of the World (as on 28. 01. 2006)

Sl. No.

Name of the City

Country

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25.

Tokyo Mexico city Seoul New York Sao Paulo Mumbai Delhi Shanghai Los Angeles Osaka Jakarta Kolkata Cairo Manila Karachi Moscow Buenos Aires Dhaka Rio de Janeiro Beijing London Tehran Istanbul Lagos Shenzhen

Japan Mexico South Korea U.S.A. Brazil India India China U.S.A. Japan Indonesia India Egypt Philippines Pakistan Russia Argentina Bangladesh Brazil China G. Britain Iran Turkey Nigeria China

Population (in millions) 34.2 22.8 22.3 21.9 20.2 19.9 19.7 18.2 18.0 16.8 16.6 15.7 15.6 15.0 14.3 13.8 13.5 13.3 12.2 12.1 12.0 11.9 11.5 11.1 10.7

Source: www.citypopulation.de/World.html

They also lack infrastructure such as, electricity, sewage disposal, health and education facilities.

Rural/Urban Problems Can you identify the problems faced by your city/town/ village in terms of any one of the following? Availability of potable water. Electricity supply. Sewerage system. Transportation and communication facilities. Health and educational infrastructure. Water and air pollution. Can you think of solutions to these problems?

Human Settlements

99

Problems of Urban Settlements

Economic Problems

People flock to cities to avail of employment opportunities and civic amenities. Since most cities in developing countries are unplanned, it creates severe congestion. Shortage of housing, vertical expansion and growth of slums are characteristic features of modern cities of developing countries. In many cities an increasing proportion of the population lives in substandard housing, e.g. slums and squatter settlements. In most million plus cities in India, one in four inhabitants lives in illegal settlements, which are growing twice as fast as the rest of the cities. Even in the Asia Pacific countries, around 60 per cent of the urban population lives in squatter settlements.

The decreasing employment opportunities in the rural as well as smaller urban areas of the developing countries consistently push the population to the urban areas. The enormous migrant population generates a pool of unskilled and semi-skilled labour force, which is already saturated in urban areas. Socio-cultural Problems Cities in the developing countries suffer from several social ills. Insufficient financial resources fail to create adequate social infrastructure catering to the basic needs of the huge population. The available educational and health facilities remain beyond the reach of the urban poor. Health indices also, present a gloomy picture in cities of developing countries. Lack of employment and education tends to aggravate the crime rates. Male selective migration to the urban areas distorts the sex ratio in these cities. Environmental Problems

Fig. 10.11: Slums

What is a Healthy City? World Health Organisation (WHO) suggests that, among other things, a ‘healthy city’ must have: A ’Clean’ and ‘Safe’ environment. Meets the ‘Basic Needs’ of ‘All’ its inhabitants. Involves the ‘Community’ in local government. Provides easily accessible ‘Health’ service.

100

Fundamentals of Human Geography

The large urban population in developing countries not only uses but also disposes off a huge quantity of water and all types of waste materials. Many cities of the developing countries even find it extremely difficult to provide the minimum required quantity of potable water and water for domestic and industrial uses. An improper sewerage system creates unhealthy conditions. Massive use of traditional fuel in the domestic as well as the industrial sector severely pollutes the air. The domestic and industrial wastes are either let into the general sewerages or dumped without treatment at unspecified locations. Huge concrete structures erected to accommodate the population and economic play a very conducive role to create heat islands.

Urban Strategy y The United Nations Development Programme (UNDP) has outlined these priorities as part of its ‘Urban Strategy’.

Increasing ‘Shelter’ for the urban poor. Provision of basic urban services such as ‘Education’, ‘Primary Health care’, ‘Clean Water and Sanitation’. Improving women’s access to ‘Basic Services’ and government facilities. Upgrading ‘Energy’ use and alternative ‘Transport’ systems. Reducing ‘Air Pollution’.

Cities, towns and rural settlements are linked through the movements of goods, resources and people. Urban-rural linkages are of crucial importance for the sustainability of human

settlements. As the growth of rural population has outpaced the generation of employment and economic opportunities, rural-to-urban migration has steadily increased, particularly in the developing countries, which has put an enormous pressure on urban infrastructure and services that are already under serious stress. It is urgent to eradicate rural poverty and to improve the quality of living conditions, as well as to create employment and educational opportunities in rural settlements. Full advantage must be taken of the complementary contributions and linkages of rural and urban areas by balancing their different economic, social and environmental requirements.

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i)

(ii)

(iii)

(iv)

(v)

Which one of the following forms of settlement develops along either side of roads, rivers or canals? (a) circular

(c)

cross-shaped

(b) linear

(d)

square

Which one of the following types of economic activities dominates in all rural settlement? (a) primary

(c)

secondary

(b) tertiary

(d)

quaternary

In which of the following regions has the oldest well-documented urban settlement found? (a) Huang He Valley

(c)

Nile Valley

(b) Indus Valley

(d)

Mesopotamia

How many of the following cities in India have attained the million status at the beginning of 2006? (a) 40

(c)

41

(b) 42

(d)

43

Sufficiency of which type of resources can help to create adequate social infrastructure catering to the needs of the large population in the developing countries? (a) financial

(c) natural

(b) human

(d) social

Human Settlements

101

2.

Answer the following questions in about 30 words. (i) (ii)

3.

How would you define a settlement? Distinguish between site and situation.

(iii)

What are the bases of classifying settlements?

(iv)

How would you justify the study of human settlements in human geography?

(v)

Identify the types of settlement shown in the photograph and write a brief note on it.

Answer the following questions in not more than 150 words. (i) (ii)

What are rural and urban settlements? Mention their characteristics. Discuss the problems associated with urban settlements in developing countries.

Project/Activity (i)

Do you live in a city? If not, do you live nearby? Is your life somehow linked to a city? (a) What is its name? (b) When was it first settled? (c) Why was the site chosen? (d) What is its population? (e) What are the functions it performs? (f) On a sketch of the city, try to identify the areas where these functions are performed. Each student should make a list of five things associated with the selected city; things that cannot be found elsewhere. This is a mini definition of the city as each student sees it. The lists should be shared with the class. How much agreement is there between the lists? (ii)

102

Can you think of some ways by which you can single handedly help reduce pollution levels of your settlement Hints : (a) Proper garbage disposal (b) Using public transport (c) Better management of domestic water consumption (d) Planting trees in the neighbourhood

Fundamentals of Human Geography

The people of a country are its real wealth. It is they who make use of the country’s resources and decide its policies. Ultimately a country is known by its people. It is important to know how many women and men a country has, how many children are born each year, how many people die and how? Whether they live in cities or villages, can they read or write and what work do they do? These are what you will study about in this unit. The world at the beginning of 21st century recorded the presence of over 6 billion population. We shall discuss the patterns of their distribution and density here.

Unit-II Chapter-2

Why do people prefer to live in certain regions and not in others?

The World Population Distribution, Density and Growth

The population of the world is unevenly distributed. The remark of George B. Cressey about the population of Asia that “Asia has many places where people are few and few place where people are very many” is true about the pattern of population distribution of the world also.

PATTERNS OF POPULATION DISTRIBUTION IN THE WORLD

11.15

eria Nig

12.92

Fig. 2.1: Most Populous Countries

Jap an 12.69

CIS 14.69

lad esh

Ba ng

tan 15.65

il 17.01 az

kis Pa

Br

es on

US

A

ia 21.21

28.14

127.76

102.7

ia Ind

Ind

Ralph Waldo Emerson

ina

(Wo)men who for truth and honour’s sake, stand fast and suffer long (Wo)men who toil while others sleep – who dare while others flee – they build a nation’s pillars deep and lift it to the sky.

130 120 110 100 90 80 70 60 50 40 30 20 10 0

Ch

Not gold but only (Wo)men can make a people great and strong.

Population (in crore)

Patterns of population distribution and density help us to understand the demographic characteristics of any area. The term population distribution refers to the way people are spaced over the earth’s surface. Broadly, 90 per cent of the world population lives in about 10 per cent of its land area. The 10 most populous countries of the world contribute about 60 per cent of the world’s population. Of these 10 countries, 6 are located in Asia. Identify these six countries of Asia.

DENSITY OF POPULATION Each unit of land has limited capacity to support people living on it. Hence, it is necessary to understand the ratio between the numbers of people to the size of land. This ratio is the density of population. It is usually measured in persons per sq km Population Area For example, area of Region X is 100 sq km and the population is 1,50,000 persons. The density of population is calculated as: Density of Population =

1,50,000 100 = 1,500 person/sq km What does this tell you about Region X? Look at the map given below: Do you observe that some areas are really crowded? These are the densely populated parts of the world with more than 200 persons Density =

on every sq km. These are the North -Eastern part of U.S.A., North-Western part of Europe, South, South-East and East Asia. Other areas like those near the North and South Poles, the hot and the cold deserts and high rainfall zones near the Equator have very low density of population. These are the sparsely populated regions of the world with less than 01 person per sq km. In between these two types are the areas of medium density. There are 11 to 50 persons per sq km in these areas. Western China, Southern India in Asia, Norway, Sweden in Europe are some examples. Look at the Fig. 2.2 and identify some other areas.

FACTORS INFLUENCING THE DISTRIBUTION OF POPULATION I.

Geographical Factors (i) Availability of water: It is the most important factor for life. So, people prefer

Fig. 2.2: World Density of Population, 2001

The World Population: Distribution, Density and Growth

9

to live in areas where fresh water is easily available. Water is used for drinking, bathing and cooking – and also for cattle, crops, industries and navigation. It is because of this that river valleys are among the most densely populated areas of the world. (ii) Landforms: People prefer living on flat plains and gentle slopes. This is because such areas are favourable for the production of crops and to build roads and industries. The mountainous and hilly areas hinder the development of transport network and hence initially do not favour agricultural and industrial development. So, these areas tend to be less populated. The Ganga plains are among the most densely populated areas of the world while the mountains zones in the Himalayas are scarcely populated. (iii) Climate: An extreme climate such as very hot or cold deserts are uncomfortable for human habitation. Areas with a comfortable climate, where there is not much seasonal variation attract more people. Areas with very heavy rainfall or extreme and harsh climates have low population. Mediterranean regions were inhabited from early periods in history due to their pleasant climate. (iv) Soils: Fertile soils are important for agricultural and allied activities. Therefore, areas which have fertile loamy soils have more people living on them as these can support intensive agriculture. Can you name some areas in India which are thinly populated due to poor soils?

II.

Economic Factors

(i) Minerals: Areas with mineral deposits attract industries. Mining and industrial activities generate employment. So, skilled and semi–skilled workers move to these areas and make them densely populated. Katanga Zambia copper belt in Africa is one such good example. (ii) Urbanisation: Cities offer better employment opportunities, educational and medical facilities, better means of transport and communication. Good civic 10

Fundamentals of Human Geography

amenities and the attraction of city life draw people to the cities. It leads to rural to urban migration and cities grow in size. Mega cities of the world continue to attract large number of migrants every year.

Yet city life can be very taxing…. think of some of the unpleasant aspects of city life.

(iii) Industrialisation: Industrial belts provide job opportunities and attract large numbers of people. These include not just factory workers but also transport operators, shopkeepers, bank employees, doctors, teachers and other service providers. The Kobe-Osaka region of Japan is thickly populated because of the presence of a number of industries.

III. Social and Cultural Factors Some places attract more people because they have religious or cultural significance. In the same way – people tend to move away from places where there is social and political unrest. Many a times governments offer incentives to people to live in sparsely populated areas or move away from overcrowded places. Can you think of some examples from your region?

POPULATION GROWTH The population growth or population change refers to the change in number of inhabitants of a territory during a specific period of time. This change may be positive as well as negative. It can be expressed either in terms of absolute numbers or in terms of percentage. Population change in an area is an important indicator of economic development, social upliftment and historical and cultural background of the region.

Some Basic Concepts of Population Geography Growth of Population : Change of population in particular area between two points of time is known as growth of

population. For example, if we deduct the population of India 1991 (84.63 crore) from population of 2001 (102.70 crore) then we shall get the growth of population (18.07 crores) in actual numbers.

thousand of population in a particular region. CDR is calculated as:

Growth Rate of Population : This is the change of population expressed in percentage.

Here, CDR=Crude Death Rate; D= Number of deaths; P=Estimated mid-year population of that year. By and large mortality rates are affected by the region’s demographic structure, social advancement and levels of its economic development.

Natural Growth of Population: This is the population increased by difference between births and deaths in a particular region between two points of time. Natural Growth = Births – Deaths Actual Growth of Population : This is Births – Deaths + In Migration – Out Migration Positive Growth of Population: This happens when the birth rate is more than the death rate between two points of time or when people from other countries migrate permanently to a region. Negative Growth of Population: If the population decreases between two points of time it is known as negative growth of population. It occurs when the birth rate falls below the death rate or people migrate to other countries.

Components of Population Change There are three components of population change – births, deaths and migration. The crude birth rate (CBR) is expressed as number of live births in a year per thousand of women. It is calculated as: Bi CBR = ¥ 1000 P Here, CBR = Crude Birth Rate; Bi = live births during the year; P=Mid year population of the area. Death rate plays an active role in population change. Population growth occurs not only by increasing births rate but also due to decreasing death rate. Crude Death Rate (CDR) is a simple method of measuring mortality of any area. CDR is expressed in terms of number of deaths in a particular year per

CDR =

D ¥ 1000 P

Migration Apart from birth and death there is another way by which the population size changes. When people move from one place to another, the place they move from is called the Place of Origin and the place they move to is called the Place of Destination. The place of origin shows a decrease in population while the population increases in the place of destination. Migration may be interpreted as a spontaneous effort to achieve a better balance between population and resources. Migration may be permanent, temporary or seasonal. It may take place from rural to rural areas, rural to urban areas, urban to urban areas and urban to rural areas. Do you realise that the same person is both an immigrant and an emigrant? Immigration: Migrants who move into a new place are called Immigrants. Emigration: Migrants who move out of a place are called Emigrants. Can you think of reasons why people migrate?

People migrate for a better economic and social life. There are two sets of factors that influence migration. The Push factors make the place of origin seem less attractive for reasons like unemployment, poor living conditions, political turmoil, unpleasant climate, natural disasters, epidemics and socio-economic backwardness. The Pull factors make the place of destination seem more attractive than the place

The World Population: Distribution, Density and Growth

11

Observe the news items and think of some reasons why certain countries become attractive destinations for migrants. Migration to cities are traditionally age and sex selective i.e. more men of working age groups move to cities. Can you think of some reason why 22 per cent of migrants to Mumbai are kids?

of origin for reasons like better job opportunities and living conditions, peace and stability, security of life and property and pleasant climate.

TRENDS IN POPULATION GROWTH The population on the earth is more than six billion. It has grown to this size over centuries. In the early periods population of the world

grew very slowly. It is only during the last few hundred years that population has increased at an alarming rate. Fig. 2.3 tells the story of population growth. After the evolution and introduction of agriculture about 8,000 to 12,000 years ago, the size of population was small – roughly 8 million. In the first century A.D. it was below World population in billions

Technological revolutions 1650 to present Information and computers Biotechnology

Number of years for world population to increase by 1 billion 6 billion 1999 (12 years) 5 billion 1987 (12 years) 4 billion 1975 (15 years) 3 billion 1960 (30 years) 2 billion

Sanitation and Medical

1930

Transportation Industrial Development and spread of agriculture

(100 years)

Age of European exploration, colonisation and settlement

(0.25 billion) (0.5 billion)

12000 years before present

Birth of Christ

1600

1 billion 1700

1800

1900

2000 Present

Time Fig. 2.3: Resource, Technology and Population Growth

12

Fundamentals of Human Geography

1830

Table 2.1: Doubling Time of World Population

Period 10,000 B.C. 1650 A.D. 1850 A.D. 1930 A.D. 1975 A.D. 2012 A.D.

Population

Time in which Population Doubles

5 million 500 million 1,000 million 2,000 million 4,000 million 8,000 million projected figure

300 million. The expanding world trade during the sixteenth and seventeenth century, set the stage for rapid population growth. Around 1750, at the dawn of the Industrial Revolution, the world population was 550 million. World population exploded in the eighteenth century after the Industrial Revolution. Technological advancement achieved so far helped in the reduction of birth rate and provided a stage for accelerated population growth.

How Science and Technology helped Population Growth? The steam engine replaced human and animal energy and also provided mechanised energy of water and wind. This increased agricultural and industrial production. Inoculation against epidemics and other communicable diseases, improvement in medical facilities and sanitation contributed to a rapid decline in death rates throughout the world.

1,500 years 200 years 80 years 45 years 37 years

it took only 12 years for it to rise from 5 billion to 6 billion. See the Table 2.1 carefully which shows that doubling time of world population is reducing fast. There is a great variation among regions in doubling their population. Table 2.2 shows that developed countries are taking more time to double their population as compared to developing countries. Most of the population growth is taking place in the developing world, where population is exploding. Why is this so? Table 2.2: Population Growth Rates (%) 1995-2000

High Liberia Somalia Yemen Saudi Arabia Oman

Low 8.2 4.2 3.7 3.4 3.3

Latvia Estonia Russia, Ukraine Albania, Bulgaria Croatia Slovania, Czech Republic Germany, Portugal Spain, Italy Denmark

–1.5 –1.2 –0.6

–0.1 0

SPATIAL PATTERN OF POPULATION CHANGE Human population increased more than ten times in the past 500 hundred years. In the twentieth century itself the population has increased four times. Nearly 80 million people are added each year.

DOUBLING TIME OF WORLD POPULATION It took more than a million years for the human population to attain the one billion mark. But

Population growth in different parts of the world can be compared. The growth of population is low in developed countries as compared to developing countries. There is negative correlation between economic development and population growth. Although the annual rate of population change (1.4 per cent) seems to be low (Table 2.3), it is actually not so. This is because: • When a small annual rate is applied to a very large population, it will lead to a large population change.

The World Population: Distribution, Density and Growth

13

Figure 2.4: Population Doubling Time

•

Even if the growth rate continues to decline, the total population grows each year. The infant mortality rate may have increased as has the death rate during childbirth.

Table 2.3: Growth of Population 2004-05 over 1990-95

Growth Rate Region

1990-95

2004-05 (Estimated)

World Africa Europe North & Central America South America Asia Oceania

1.6 2.4 0.2 1.4 1.7 1.6 1.5

1.4 2.6 0.0 1.1 1.4 1.4 1.3

(Australia, New Zealand and Fiji)

IMPACT OF POPULATION CHANGE A small increase in population is desirable in a growing economy. However, population growth beyond a certain level leads to problems. Of

14

Fundamentals of Human Geography

these the depletion of resources is the most serious. Population decline is also a matter of concern. It indicates that resources that had supported a population earlier are now insufficient to maintain the population. The deadly HIV/AIDS epidemics in Africa and some parts of the Commonwealth of Independent States (CIS) and Asia have pushed up death rates and reduced average life expectancy. This has slowed down population growth.

The Doubling Story... It will take 36 years The annual population growth rate in India is 1.9 per cent. At this rate India’s population of over 1 billion will double in 36 years. Some developed countries will take 318 years to double their population whereas some countries still do not show symptoms of doubling their population.

DEMOGRAPHIC TRANSITION Demographic transition theory can be used to describe and predict the future population of any area. The theory tells us that population of any region changes from high births and high deaths to low births and low deaths as society progresses from rural agrarian and illiterate to urban industrial and literate society. These changes occur in stages which are collectively known as the demographic cycle. Rural, Demographic Urban, Agrarian Transition Industrial

The Fig. 2.5 explains the three-staged model of Demographic Transition Theory: High Fluctuating Stage I

Stage II

Stage III

Expanding BR

engaged in agriculture where large families are an asset. Life expectancy is low, people are mostly illiterate and have low levels of technology. Two hundred years ago all the countries of the world were in this stage. Fertility remains high in the beginning of second stage but it declines with time. This is accompanied by reduced mortality rate. Improvements in sanitation and health conditions lead to decline in mortality. Because of this gap the net addition to population is high. In the last stage, both fertility and mortality decline considerably. The population is either stable or grows slowly. The population becomes urbanised, literate and has high technical knowhow and deliberately controls the family size. This shows that human beings are extremely flexible and are able to adjust their fertility. In the present day, different countries are at different stages of demographic transition.

CBR/CDR

35 Natural Increase in Population

15

Bangladesh Present Rainforest tribes World examples

POPULATION CONTROL MEASURES Low Fluctuating

DR

Peru

Sri Lanka Kenya

Canada Japan USA

Time

Fig. 2.5: Demographic Transition Theory

The first stage has high fertility and high mortality because people reproduce more to compensate for the deaths due to epidemics and variable food supply. The population growth is slow and most of the people are

Family planning is the spacing or preventing the birth of children. Access to family planning services is a significant factor in limiting population growth and improving women’s health. Propaganda, free availability of contraceptives and tax disincentives for large families are some of the measures which can help population control. Thomas Malthus in his theory (1793) stated that the number of people would increase faster than the food supply. Any further increase would result in a population crash caused by famine, disease and war. The preventive checks are better than the physical checks. For the sustainability of our resources, the world will have to control the rapid population increase

The World Population: Distribution, Density and Growth

15

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i) Which one of the following continents has the highest growth of population? (a) Africa (c) Asia (b) South America (d) North America (ii) Which one of the following is not an area of sparse population? (a) The Atacama (c) Equatorial region (b) South-east Asia (d) Polar regions (iii) Which one of the following is not a push factor ? (a) Water shortage (c) Unemployment (b) Medical/educational facilities (d) Epidemics (iv) Which one of the following is not a fact ? (a) Human population increased more than ten times during the past 500 years. (b) Nearly 80 million people are added to the world population each year. (c) It took 100 years for the population to rise from 5 billion to 6 billion. (d) Population growth is high in the first stage of demographic transition?

2.

Answer the following questions in about 30 words. (i) Name three geographical factors that influence the distribution of population. (ii) There are a number of areas with high population density in the world. Why does this happen? (iii) What are the three components of population change?

3.

Distinguish between: (i) Birth rate and death rate. (ii) Push factors and pull factors of migration.

4.

Answer the following questions in about 150 words. (i) Discuss the factors influencing the distribution and density of population in the world. (ii) Discuss the three stages of demographic transition.

Map Skill On the outline map of the world, show and name the following. (i) Countries of Europe and Asia with negative growth rate of population. (ii) African countries with growth rate of population more than three per cent. (You may refer to Appendix 1).

Project/Activity (i) (ii)

16

Has someone in your family migrated? Write about her/his place of destination. What made her/him migrate? Write a brief report on the distribution and density of population in your state.

Fundamentals of Human Geography

Unit-II Chapter-3

People of any country are diverse in many respects. Each person is unique in her/his own way. People can be distinguished by their age, sex and their place of residence. Some of the other distinguishing attributes of the population are occupation, education and life expectancy.

SEX COMPOSITION The number of women and men in a country is an important demographic characteristic. The ratio between the number of women and men in the population is called the Sex Ratio. In some countries it is calculated by using the formula:

Population Composition

Male Population × 1000 Female Population

or the number of males per thousand females. In India, the sex ratio is worked out using the formula:

Female Population × 1000 Male Population or the number of females per thousand males.

The sex ratio is an important information about the status of women in a country. In regions where gender discrimination is rampant, the sex ratio is bound to be unfavourable to women. Such areas are those where the practice of female foeticide, female infanticide and domestic violence against women are prevalent. One of the reasons could be lower socio-economic status of women in these areas. You must remember that more women in the population does not mean they have a better status. It could be that the men might have migrated to other areas for employment.

Natural Advantage v/s Social Disadvantage Females have a biological advantage over males as they tend to be more resilient than males yet this advantage is cancelled out by the social disadvantages and discriminations that they face.

Fig. 3.1, 3.2 and 3.3 show different types of population pyramids. Expanding Populations The age-sex pyramid of Nigeria as you can see is a triangular shaped pyramid with a wide base and is typical of less developed countries. These have larger populations in lower age groups due to high birth rates. If you construct the pyramids for Bangladesh and Mexico, it would look the same. NIGERIA, 2003

Age Groups Years

On an average, the world population reflects a sex ratio of 990 females per 1000 males. The highest sex ratio in the world has been recorded in Latvia which is 1187 females per 1000 males. In contrast, the lowest sex ratio occurs in U.A.E. which is 468 females per 1000 males. The world pattern of sex ratio does not exhibit variations in the developed regions of the world. The sex ratio is favourable for females in 139 countries of the world and unfavourable for them in the remaining 72 countries listed by the United Nations. In general, Asia has a low sex ratio. Countries like China, India, Saudi Arabia, Pakistan, Afghanistan have a lower sex ratio. On the other extreme is greater part of Europe (including Russia) where males are in minority. A deficit of males in the populations of many European countries is attributed to better status of women, and an excessively male-dominated out-migration to different parts of the world in the past.

80+ 75-79 70-74 65-69 60-64 55-59 50-54 45-49 40-44 35-39 30-34 25-29 20-24 15-19 10-14 5-9 0-4

MALE

10

Age structure represents the number of people of different age groups. This is an important indicator of population composition, since a large size of population in the age group of 1559 indicates a large working population. A greater proportion of population above 60 years represents an ageing population which requires more expenditure on health care facilities. Similarly high proportion of young population would mean that the region has a high birth rate and the population is youthful. Age-Sex Pyramid The age-sex structure of a population refers to the number of females and males in different age groups. A population pyramid is used to show the age-sex structure of the population. The shape of the population pyramid reflects the characteristics of the population. The left side shows the percentage of males while the right side shows the percentage of women in each age group. 18

Fundamentals of Human Geography

8

6

4

2

0

2

6

4

8

10

Per cent Data source: Demographic Year Book, 2003, United Nations Statistics Division. Data refer to national projection

Fig. 3.1: Expanding Population

Constant Population Australia’s age-sex pyramid is bell shaped and tapered towards the top. This shows birth and death rates are almost equal leading to a near constant population. AUSTRALIA, 2003

Age Groups Years

Age Structure

FEMALE

85+ 80-84 75-79 70-74 65-69 60-64 55-59 50-54 45-49 40-44 35-39 30-34 25-29 20-24 15-19 10-14 5-9 0-4

MALE

10

8

6

FEMALE

4

2

0

2

4

6

8

10

Per cent Data source: Demographic Year Book, 2003, United Nations Statistics Division.

Fig. 3.2: Constant Population

Declining Populations The Japan pyramid has a narrow base and a tapered top showing low birth and death rates. The population growth in developed countries is usually zero or negative.

Age Groups Years

JAPAN, 2003 85+ 80-84 75-79 70-74 65-69 60-64 55-59 50-54 45-49 40-44 35-39 30-34 25-29 20-24 15-19 10-14 5-9 0-4

MALE

10

8

6

FEMALE

4

2

0

2

4

6

8

10

Per cent

Data source: Demographic Year Book, 2003, United Nations Statistics Division. Excluding diplomatic personnel outside the country and foreign military and civilian personnel and their dependants stationed in the area

Fig. 3.3: Declining Population

Draw a population pyramid of the children in your school and describe its characteristics.

Ageing Population Population ageing is the process by which the share of the older population becomes proportionally larger. This is a new phenomenon of the twentieth century. In most of the developed countries of the world, population in higher age groups has increased due to increased life expectancy. With a reduction in birth rates, the proportion of children in the population has declined.

RURAL URBAN COMPOSITION The division of population into rural and urban is based on the residence. This division is necessary because rural and urban life styles differ from each other in terms of their livelihood and social conditions. The age-sex-occupational structure, density of population and level of development vary between rural and urban areas.

The criteria for differentiating rural and urban population varies from country to country. In general terms rural areas are those where people are engaged in primary activities and urban areas are those when majority of the working population is engaged in non-primary activities. Fig. 3.4 shows rural urban sex composition of selected countries. The rural and urban differences in sex ratio in Canada and West European countries like Finland are just the opposite of those in African and Asian countries like Zimbabwe and Nepal respectively. In Western countries, males outnumber females in rural areas and females outnumber the males in urban areas. In countries like Nepal, Pakistan and India the case is reverse. The excess of females in urban areas of U.S.A., Canada and Europe is the result of influx of females from rural areas to avail of the vast job opportunities. Farming in these developed countries is also highly mechanised and remains largely a male occupation. By contrast the sex ratio in Asian urban areas remains male dominated due to the predominance of male migration. It is also worth noting that in countries like India, female participation in farming activity in rural area is fairly high. Shortage of housing, high cost of living, paucity of job opportunities and lack of security in cities, discourage women to migrate from rural to urban areas.

Literacy Proportion of literate population of a country in an indicator of its socio-economic development as it reveals the standard of living, social status of females, availability of educational facilities and policies of government. Level of economic development is both a cause and consequence of literacy. In India – literacy rate denotes the percentage of population above 7 years of age, who is able to read, write and have the ability to do arithmetic calculations with understanding.

Occupational Structure The working population (i.e. women and men of the age group – 15 to 59) take part in various occupations ranging from agriculture, forestry, Population Composition

19

1200

1083 986

Females per 1000 Males

1000

1040 941

1063

1051 935

1129 1007

Rural Urban

1012 939

908

800

600

400

200

0

Finland

Canada

New Zealand

Brazil

Zimbabwe

Nepal

Fig. 3.4: Rural Urban Sex Composition, 2003 (Selected Countries)

fishing, manufacturing construction, commercial transport, services, communication and other unclassified services. Agriculture, forestry, fishing and mining are classified as primary activities manufacturing as secondary, transport, communication and other services as tertiary and the jobs related to research and developing ideas as quaternary activities. The proportion of working population engaged in these four

sectors is a good indicator of the levels of economic development of a nation. This is because only a developed economy with industries and infrastructure can accommodate more workers in the secondary, tertiary and quaternary sector. If the economy is still in the primitive stages, then the proportion of people engaged in primary activities world be high as it involves extraction of natural resources.

EXERCISES 1. Choose the right answer from the four alternatives given below. (i)

Which one of the following has caused the sex ratio of the United Arab Emirates to be low? (a)

20

Selective migration of male working population

(b)

High birth rate of males

(c)

Low birth rate of females

(d)

High out migration of females

Fundamentals of Human Geography

(ii)

(iii)

Which one of the following figures represents the working age group of the population? (a)

15 to 65 years

(c)

15 to 66 years

(b)

15 to 64 years

(d)

15 to 59 years

Which one of the following countries has the highest sex ratio in the world? (a)

Latvia

(c)

Japan

(b)

United Arab Emirates

(d)

France

2. Answer the following questions in about 30 words. (i) (ii) (iii)

What do you understand by population composition? What is the significance of age-structure? How is sex-ratio measured?

3. Answer the following questions in not more than 150 words. (i) (ii)

Describe the rural-urban composition of the population. Discuss the factors responsible for imbalances in the sex-age found in different parts of the world and occupational structure.

Project/Activity Construct an age-sex pyramid for your district/state.

Population Composition

21

Unit-II Chapter-4

The words ‘growth’ and ‘development’ are not new to you. Look around you, almost everything that you can see (and many that you cannot) grows and develops. These may be plants, cities, ideas, nations, relationships or even you yourself! What does this mean?

Do growth and development mean the same thing? Do they accompany each other?

This chapter discusses the concept of human development as it pertains to nations and communities.

Human Development

GROWTH AND DEVELOPMENT Both growth and development refer to changes over a period of time. The difference is that growth is quantitative and value neutral. It may have a positive or a negative sign. This means that the change may be either positive (showing an increase) or negative (indicating a decrease). Development means a qualitative change which is always value positive. This means that development cannot take place unless there is an increment or addition to the existing conditions. Development occurs when positive growth takes place. Yet, positive growth does not always lead to development. Development occurs when there is a positive change in quality. For example, if the population of a city grows from one lakh to two lakhs over a period of time, we say the city has grown. However, if a facilities like housing, provision of basic services and other characteristics remain the same, then this growth has not been accompanied by development. Can you think of a few more examples to differentiate between growth and development?

Write a short essay or draw a set of pictures illustrating growth without development and growth with development.

For many decades, a country’s level of development was measured only in terms of its

Band Aceh, June, 2004

Band Aceh, December, 2004

Do you know that cities can also grow negatively? Look at the photographs of this tsunami affected city. Are natural disasters the only reasons for negative growth in a city’s size?

economic growth. This meant that the bigger the economy of the country, the more developed it was considered, even though this growth did not really mean much change in the lives of most people. The idea that the quality of life people enjoy in a country, the opportunities they have and freedoms they enjoy, are important aspects of development, is not new. These ideas were clearly spelt out for the first time in the late eighties and early nineties. The works of two South Asian economists, Mahbub-ul-Haq and Amartya Sen are important in this regard.

The concept of human development was introduced by Dr Mahbub-ul-Haq. Dr Haq has described human development as development that enlarges people’s choices and improves their lives. People are central to all development under this concept. These choices are not fixed but keep on changing. The basic goal of development is to create conditions where people can live meaningful lives. A meaningful life is not just a long one. It must be a life with some purpose. This means that people must be healthy, be able to develop their talents, participate in society and be free to achieve their goals.

Dr Mahbub-ul-Haq and Prof Amartya Sen were close friends and have worked together under the leadership of Dr Haq to bring out the initial Human Development Reports. Both these South Asian economists have been able to provide an alternative view of development. A man of vision and compassion, Pakistani economist Dr Mahbub-ul-Haq created the Human Development Index in 1990. According to him, development is all about enlarging people’s choices in order to lead long, healthy lives with dignity. The United Nations Development Programme has used his concept of human development to publish the Human Development Report annually since 1990. Dr Haq’s flexibility of mind and ability to think out of the box can be illustrated from one of his speeches where he quoted Shaw saying, “‘You see things that are, and ask why? I dream of things that never were, and ask why not?’ Nobel Laureate Prof Amartya Sen saw an increase in freedom (or decrease in unfreedom) as the main objective of development. Interestingly, increasing freedoms is also one of the most effective ways of bringing about development. His work explores the role of social and political institutions and processes in increasing freedom. The works of these economists are path breaking and have succeeded in bringing people to the centre of any discussion on development. Human Development

23

What is a Meaningful Life?

Which of these lives is a meaningful life?

Who do you think leads more meaningful life? What makes one of these more meaningful than the other? 24

Fundamentals of Human Geography

Leading a long and healthy life, being able to gain knowledge and having enough means to be able to live a decent life are the most important aspects of human development. Therefore, access to resources, health and education are the key areas in human development. Suitable indicators have been developed to measure each of these aspects. Can you think of some? Very often, people do not have the capability and freedom to make even basic choices. This may be due to their inability to acquire knowledge, their material poverty, social discrimination, inefficiency of institutions and other reasons. This prevents them from leading healthy lives, being able to get educated or to have the means to live a decent life. Building people’s capabilities in the areas of health, education and access to resources is therefore, important in enlarging their choices. If people do not have capabilities in these areas, their choices also get limited. For example, an uneducated child cannot make the choice to be a doctor because her choice has got limited by her lack of education. Similarly, very often poor people cannot choose to take medical treatment for disease because their choice is limited by their lack of resources.

Enact a five-minute play with your classmates showing how choices are limited due to lack of capability in the areas of either income, education or health.

THE FOUR PILLARS OF HUMAN DEVELOPMENT Just as any building is supported by pillars, the idea of human development is supported by the concepts of equity, sustainability, productivity and empowerment. Equity refers to making equal access to opportunities available to everybody. The opportunities available to people must be equal irrespective of their gender, race, income and in the Indian case, caste. Yet this is very often not the case and happens in almost every society.

For example, in any country, it is interesting to see which group the most of the school dropouts belong to. This should then lead to an understanding of the reasons for such behaviour. In India, a large number of women and persons belonging to socially and economically backward groups drop out of school. This shows how the choices of these groups get limited by not having access to knowledge. Sustainability means continuity in the availability of opportunities. To have sustainable human development, each generation must have the same opportunities. All environmental, financial and human resources must be used keeping in mind the future. Misuse of any of these resources will lead to fewer opportunities for future generations. A good example is about the importance of sending girls to school. If a community does not stress the importance of sending its girl children to school, many opportunities will be lost to these young women when they grow up. Their career choices will be severely curtailed and this would affect other aspects of their lives. So each generation must ensure the availability of choices and opportunities to its future generations. Productivity here means human labour productivity or productivity in terms of human work. Such productivity must be constantly enriched by building capabilities in people. Ultimately, it is people who are the real wealth of nations. Therefore, efforts to increase their knowledge, or provide better health facilities ultimately leads to better work efficiency. Empowerment means to have the power to make choices. Such power comes from increasing freedom and capability. Good governance and people-oriented policies are required to empower people. The empowerment of socially and economically disadvantaged groups is of special importance.

Talk to the vegetable vendor in your neighbourhood and find out if she has gone to school. Did she drop out of school? Why? What does this tell you about her choices and the freedom she has? Note how her opportunities were limited because of her gender, caste and income. Human Development

25

APPROACHES TO HUMAN DEVELOPMENT There are many ways of looking at the problem of human development. Some of the important approaches are: (a) The income approach; (b) The welfare approach; (c) Minimum needs approach; and (d) Capabilities approach (Table 4.1).

MEASURING HUMAN DEVELOPMENT The human development index (HDI) ranks the countries based on their performance in the key areas of health, education and access to resources. These rankings are based on a score between 0 to 1 that a country earns from its record in the key areas of human development. The indicator chosen to assess health is the life expectancy at birth. A higher life expectancy means that people have a greater chance of living longer and healthier lives. The adult literacy rate and the gross enrolment ratio represent access to knowledge. The number of adults who are able to read and

write and the number of children enrolled in schools show how easy or difficult it is to access knowledge in a particular country. Access to resources is measured in terms of purchasing power (in U.S. dollars). Each of these dimensions is given a weightage of 1/3. The human development index is a sum total of the weights assigned to all these dimensions. The closer a score is to one, the greater is the level of human development. Therefore, a score of 0.983 would be considered very high while 0.268 would mean a very low level of human development. The human development index measures attainments in human development. It reflects what has been achieved in the key areas of human development. Yet it is not the most reliable measure. This is because it does not say anything about the distribution. The human poverty index is related to the human development index. This index measures the shortfall in human development.

Table 4.1: Approaches to Human Development

26

(a)

Income Approach

This is one of the oldest approaches to human development. Human development is seen as being linked to income. The idea is that the level of income reflects the level of freedom an individual enjoys. Higher the level of income, the higher is the level of human development.

(b)

Welfare Approach

This approach looks at human beings as beneficiaries or targets of all development activities. The approach argues for higher government expenditure on education, health, social secondary and amenities. People are not participants in development but only passive recipients. The government is responsible for increasing levels of human development by maximising expenditure on welfare.

(c)

Basic Needs Approach

This approach was initially proposed by the International Labour Organisation (ILO). Six basic needs i.e.: health, education, food, water supply, sanitation, and housing were identified. The question of human choices is ignored and the emphasis is on the provision of basic needs of defined sections.

(d)

Capability Approach

This approach is associated with Prof. Amartya Sen. Building human capabilities in the areas of health, education and access to resources is the key to increasing human development.

Fundamentals of Human Geography

Bhutan is the only country in the world to officially proclaim the Gross National Happiness (GNH) as the measure of the country’s progress. Material progress and technological developments are approached more cautiously taking into consideration the possible harm they might bring to the environment or the other aspects of cultural and spiritual life of the Bhutanese. This simply means material progress cannot come at the cost of happiness. GNH encourages us to think of the spiritual, non-material and qualitative aspects of development.

INTERNATIONAL COMPARISONS Since 1990, the United Nations Development Programme (UNDP) has been publishing the Human Development Report every year. This report provides a rank-wise list of all member countries according to the level of human development. The Human Development index and the Human Poverty index are two important indices to measure human development used by the UNDP.

It is a non-income measure. The probability of not surviving till the age of 40, the adult illiteracy rate, the number of people who do not have access to clean water, and the number of small children who are underweight are all taken into account to show the shortfall in human development in any region. Often the human poverty index is more revealing than the human development index. Looking at both these measures of human development together gives an accurate picture of the human development situation in a country. The ways to measure human development are constantly being refined and newer ways of capturing different elements of human development are being researched. Researchers have found links between the level of corruption or political freedom in a particular region. There is also a discussion regarding a political freedom index and, a listing of the most corrupt countries. Can you think of other links to the level of human development?

International comparisons of human development are interesting. Size of the territory and per capita income are not directly related to human development. Often smaller countries have done better than larger ones in human development. Similarly, relatively poorer nations have been ranked higher than richer neighbours in terms of human development. For example, Sri Lanka, Trinidad and Tobago have a higher rank than India in the human development index despite having smaller economies. Similarly, within India, Kerala performs much better than Punjab and Gujarat in human development despite having lower per capita income. Countries can be classified into three groups on the basis of the human development scores earned by them (Table 4.2). Table 4.2: Human Development: Categories, Criteria and Countries

Level of Human Development High Medium Low

Score in Development Index

Number of Countries

above 0.8

57

between 0.5 up to 0.799

88

below 0.5

32

Source: Human Development Report, 2005

Countries with High Index Value Countries with high human development index are those which have a score of over 0.8. Human Development

27

According to the Human Development Report of 2005, this group includes 57 countries. Table 4.3 shows the countries in this group. Table 4.3: Top Ten Countries with High Value Index

Sl. No. 1. 2. 3. 4. 5.

Country Norway Iceland Australia Luxembourg Canada

Sl. No. 6. 7. 8. 9. 10.

Country Sweden Switzerland Ireland Belgium United States

Source: Human Development Report, 2005

Try to locate these countries on a map. Can you see what these countries have in common? To find out more visit the official government websites of these countries.

Providing education and healthcare is an important government priority. Countries with higher human development are those where a lot of investment in the social sector has taken place. Altogether, a higher investment in people and good governance has set this group of countries apart from the others. Try to find out the percentage of the country’s income spent on these sectors. Can you think of some other characteristics that these countries have in common?

You will notice that many of these countries have been the former imperial powers. The degree of social diversity in these countries is not very high. Many of the countries with a high human development score are located in Europe and represent the industrialised western world. Yet there are striking numbers of non-European countries also who have made it to this list. Countries with Medium Index Value Countries with medium levels of human development form the largest group. There are a total of 88 countries in this group. Most of these are countries which have emerged in the period after the Second World War. Some countries from this group were former colonies while many others have emerged after the break up of the erstwhile Soviet Union in 1990. Many of these countries have been rapidly improving their human development score by adopting more people-oriented policies and reducing social discrimination. Most of these countries have a much higher social diversity than the countries with higher human development scores. Many in this group have faced political instability and social uprisings at some point of time in their recent history.

What could be the reasons for India to be behind 125 countries in HDI?

28

Fundamentals of Human Geography

Countries with Low Index Value As many as 32 countries record low levels of human development. A large proportion of these are small countries which have been going through political turmoil and social instability in the form of civil war, famine or a high incidence of diseases. There is an urgent need to address the human development requirements of this group through well thought out policies. International comparisons of human development can show some very interesting results. Often people tend to blame low levels of human development on the culture of the people. For example, X country has lower human development because its people follow Y religion, or belong to Z community. Such statements are misleading.

To understand why a particular region keeps reporting low or high levels of human development it is important to look at the pattern of government expenditure on the social sector. The political environment of the country and the amount of freedom people have is also important. Countries with high levels of human development invest more in the social sectors and are generally free from political turmoil and instability. Distribution of the country’s resources is also far more equitable. On the other hand, places with low levels of human development tend to spend more on defence rather than social sectors. This shows that these countries tend to be located in areas of political instability and have not been able to initiate accelerated economic development.

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i)

(ii)

(iii)

2.

(a) an increase in size

(c)

a positive change in quality

(b) a constant in size

(d)

a simple change in the quality

Which one of the following scholars introduced the concept of Human Development? (a) Prof. Amartya Sen

(c)

Dr Mahabub-ul-Haq

(b) Ellen C. Semple

(d)

Ratzel

Which one of the following is not a country with high human development? (a) Norway

(c)

Argentina

(b) Japan

(d)

Egypt

Answer the following questions in about 30 words. (i) (ii) (iii)

3.

Which one of the following best describes development?

What are the three basic areas of human development? Name the four main components of human development? How are countries classified on the basis of human development index?

Answer the following questions in not more than 150 words. (i) (ii)

What do you understand by the term human development? What do equity and sustainability refer to within the concept of human development? Human Development

29

Project/Activity Make a list of the ten most corrupt countries and ten least corrupt countries. Compare their scores on the human development index. What inferences can you draw? Consult the latest Human Development Report for this.

30

Fundamentals of Human Geography

Unit-III Chapter-5

Primary Activities

Human activities which generate income are known as economic activities. Economic activities are broadly grouped into primary, secondary, tertiary and quaternary activities. Primary activities are directly dependent on environment as these refer to utilisation of earth’s resources such as land, water, vegetation, building materials and minerals. It, thus includes, hunting and gathering, pastoral activities, fishing, forestry, agriculture, and mining and quarrying. Why inhabitants of coastal and plain regions are engaged in fishing and agriculture respectively? What are the physical and social factors which affect the type of primary activities in different regions?

People engaged in primary activities are called redcollar workers due to the outdoor nature of their work.

HUNTING AND GATHERING The earliest human beings depended on their immediate environment for their sustenance. They subsisted on: (a) animals which they hunted; and (b) the edible plants which they gathered from forests in the vicinity. Primitive societies depended on wild animals. People located in very cold and extremely hot climates survived on hunting. The people in the coastal areas still catch fish though fishing has experienced modernisation due to technological progress. Many species, now have become extinct or endangered due to illegal hunting (poaching). The early hunters used primitive tools made of stones, twigs or arrows so the number of animals killed was limited. Why has hunting been banned in India? Gathering and hunting are the oldest economic activity known. These are carried out at different levels with different orientations. Gathering is practised in regions with harsh climatic conditions. It often involves primitive societies, who extract, both plants and

animals to satisfy their needs for food, shelter and clothing. This type of activity requires a small amount of capital investment and operates at very low level of technology. The yield per person is very low and little or no surplus is produced.

Gathering is practised in: (i) high latitude zones which include northern Canada, northern Eurasia and southern Chile; (ii) Low latitude zones such as the Amazon Basin, tropical Africa, Northern fringe of Australia and the interior parts of Southeast Asia (Fig. 5.2). In modern times some gathering is marketoriented and has become commercial. Gatherers collect valuable plants such as leaves, barks of trees and medicinal plants and after simple processing sell the products in the market. They use various parts of the plants, for example, the bark is used for quinine, tanin extract and cork— leaves supply materials for beverages, drugs, cosmetics, fibres, thatch and fabrics; nuts for food and oils and tree trunk yield rubber, balata, gums and resins.

The name of the part of the chewing gum after the flavour is gone? It is called Chicle — it is made from the milky juice of zapota tree.

Fig. 5.1: Women Gathering Oranges in Mizoram

Gathering has little chance of becoming important at the global level. Products of such an

Fig. 5.2: Areas of Subsistence Gathering

32

Fundamentals of Human Geography

activity cannot compete in the world market. Moreover, synthetic products often of better quality and at lower prices, have replaced many items supplied by the gatherers in tropical forests.

PASTORALISM At some stage in history, with the realisation that hunting is an unsustainable activity, human beings might have thought of domestication of animals. People living in different climatic conditions selected and domesticated animals found in those regions. Depending on the geographical factors, and technological development, animal rearing today is practised either at the subsistence or at the commercial level. Nomadic Herding Nomadic herding or pastoral nomadism is a primitive subsistence activity, in which the herders rely on animals for food, clothing, shelter, tools and transport. They move from one place to another along with their livestock, depending on the amount and quality of pastures and water. Each nomadic community occupies a well-identified territory as a matter of tradition.

Pastoral nomadism is associated with three important regions. The core region extends from the Atlantic shores of North Africa eastwards across the Arabian peninsula into Mongolia and Central China. The second region extends over the tundra region of Eurasia. In the southern hemisphere there are small areas in South-west Africa and on the island of Madagascar (Fig. 5.4) Movement in search of pastures is undertaken either over vast horizontal distances or vertically from one elevation to another in the mountainous regions. The process of migration from plain areas to pastures on mountains during summers and again from mountain pastures to plain areas during winters is known as transhumance. In mountain regions, such as Himalayas, Gujjars, Bakarwals, Gaddis and Bhotiyas migrate from plains to the mountains in summers and to the plains from the high altitude pastures in winters. Similarly, in the tundra regions, the nomadic herders move from south to north in summers and from north to south in winters. The number of pastoral nomads has been decreasing and the areas operated by them shrinking. This is due to (a) imposition of political boundaries; (b) new settlement plans by different countries. Commercial Livestock Rearing

Fig. 5.3: Nomads taking their sheep up to the Mountains at the onset of summer

A wide variety of animals is kept in different regions. In tropical Africa, cattle are the most important livestock, while in Sahara and Asiatic deserts, sheep, goats and camel are reared. In the mountainous areas of Tibet and Andes, yak and llamas and in the Arctic and sub Arctic areas, reindeer are the most important animals.

Unlike nomadic herding, commercial livestock rearing is more organised and capital intensive. Commercial livestock ranching is essentially associated with western cultures and is practised on permanent ranches. These ranches cover large areas and are divided into a number of parcels, which are fenced to regulate the grazing. When the grass of one parcel is grazed, animals are moved to another parcel. The number of animals in a pasture is kept according to the carrying capacity of the pasture. This is a specialised activity in which only one type of animal is reared. Important animals include sheep, cattle, goats and horses. Products such as meat, wool, hides and skin are processed and packed scientifically and exported to different world markets. Rearing of animals in ranching is organised on a scientific basis. The main Primary Activities

33

Fig. 5.4: Areas of Nomadic Herding

AGRICULTURE Agriculture is practised under multiple combinations of physical and socio-economic conditions, which gives rise to different types of agricultural systems. Based on methods of farming, different types of crops are grown and livestock raised. The following are the main agricultural systems. Subsistence Agriculture

Fig. 5.5: Commercial Livestock Rearing

Reindeer rearing in the northern regions of Alaska where most of the Eskimos own about two-third of the stock.

emphasis is on breeding, genetic improvement, disease control and health care of the animals. New Zealand, Australia, Argentina, Uruguay and United States of America are important countries where commercial livestock rearing is practised (Fig. 5.6). 34

Fundamentals of Human Geography

Subsistence agriculture is one in which the farming areas consume all, or nearly so, of the products locally grown. It can be grouped in two categories — Primitive Subsistence Agriculture and Intensive Subsistence Agriculture. Primitive Subsistence Agriculture Primitive subsistence agriculture or shifting cultivation is widely practised by many tribes in the tropics, especially in Africa, south and central America and south east Asia (Fig. 5.7).

Fig. 5.6: Areas of Commercial Livestock Rearing

Fig. 5.7: Areas of Primitive Subsistence Agriculture

Primary Activities

35

The vegetation is usually cleared by fire, and the ashes add to the fertility of the soil. Shifting cultivation is thus, also called slash and burn agriculture. The cultivated patches are very small and cultivation is done with very primitive tools such as sticks and hoes. After sometime (3 to 5 years) the soil looses its fertility and the farmer shifts to another parts and clears other patch of the forest for cultivation. The farmer may return to the earlier patch after sometime. One of the major problems of shifting cultivation is that the cycle of jhum becomes less and less due to loss of fertility in different parcels. It is prevalent in tropical region in different names, e.g. Jhuming in North eastern states of India, Milpa in central America and Mexico and Ladang in Indonesia and Malaysia. Find out other areas and the names with which shifting cultivation is done. Intensive Subsistence Agriculture This type of agriculture is largely found in densely populated regions of monsoon Asia.

Basically, there are two types of intensive subsistence agriculture. (i) Intensive subsistence agriculture dominated by wet paddy cultivation: This type of agriculture is characterised by dominance of the rice crop. Land holdings are very small due to the high density of population. Farmers work with the help of family labour leading to intensive use of land. Use of machinery is limited and most of the agricultural operations are done by manual labour. Farm yard manure is used to maintain the fertility of the soil. In this type of agriculture, the yield per unit area is high but per labour productivity is low. (ii) Intensive subsidence agriculture dominated by crops other than paddy: Due to the difference in relief, climate, soil and some of the other geographical factors, it is not practical to grow paddy in many parts of monsoon Asia. Wheat, soyabean, barley and sorghum are grown in northern China, Manchuria, North Korea and North Japan. In India wheat is grown in western

Fig. 5.8: Areas of Intensive Subsistence Farming

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Fundamentals of Human Geography

coconut and sugarcane plantations in the Philippines. The Dutch once had monopoly over sugarcane plantation in Indonesia. Some coffee fazendas (large plantations) in Brazil are still managed by Europeans. Today, ownership of the majority of plantations has passed into the hands of the government or the nationals of the countries concerned.

Fig. 5.9: Rice Transplantation

parts of the Indo-Gangetic plains and millets are grown in dry parts of western and southern India. Most of the characteristics of this type of agriculture are similar to those dominated by wet paddy except that irrigation is often used. The Europeans colonised many parts in the world and they introduced some other forms of agriculture such as plantations which were mainly profit-oriented large scale production systems. Plantation Agriculture Plantation agriculture as mentioned above was introduced by the Europeans in colonies situated in the tropics. Some of the important plantation crops are tea, coffee, cocoa, rubber, cotton, oil palm, sugarcane, bananas and pineapples. The characteristic features of this type of farming are large estates or plantations, large capital investment, managerial and technical support, scientific methods of cultivation, single crop specialisation, cheap labour, and a good system of transportation which links the estates to the factories and markets for the export of the products. The French established cocoa and coffee plantations in west Africa. The British set up large tea gardens in India and Sri Lanka, rubber plantations in Malaysia and sugarcane and banana plantations in West Indies. Spanish and Americans invested heavily in

Fig. 5.10: Tea Plantation

The slopes of hills are used for tea plantations because of favourable geographical conditions.

Extensive Commercial Grain Cultivation Commercial grain cultivation is practised in the interior parts of semi-arid lands of the midlatitudes. Wheat is the principal crop, though other crops like corn, barley, oats and rye are also grown. The size of the farm is very large, therefore entire operations of cultivation from ploughing to harvesting are mechanised (Fig. 5.11). There is low yield per acre but high yield per person. Why does this happen? Fig. 5.11: Mechanised Grain Farming

Combine crews are capable of harvesting grain over many hectares in a single day. Primary Activities

37

Fig. 5.12: Areas of Extensive Commercial Grain Farming

This type of agriculture is best developed in Eurasian steppes, the Canadian and American Prairies, the Pampas of Argentina, the Velds of South Africa, the Australian Downs and the Canterbury Plains of New Zealand. (Locate these areas on the world map). Mixed Farming This form of agriculture is found in the highly developed parts of the world, e.g. North-western Europe, Eastern North America, parts of Eurasia and the temperate latitudes of Southern continents (Fig. 5.14). Mixed farms are moderate in size and usually the crops associated with it are wheat, barley, oats, rye, maize, fodder and root crops. Fodder crops are an important component of mixed farming. Crop rotation and intercropping play an important role in maintaining soil fertility. Equal emphasis is laid on crop cultivation and animal husbandry. Animals like cattle, sheep, pigs and poultry provide the main income along with crops. Mixed farming is characterised by high capital expenditure on farm machinery and 38

Fundamentals of Human Geography

building, extensive use of chemical fertilisers and green manures and also by the skill and expertise of the farmers. Dairy Farming Dairy is the most advanced and efficient type of rearing of milch animals. It is highly capital intensive. Animal sheds, storage facilities for fodder, feeding and milching machines add to the cost of dairy farming. Special emphasis is laid on cattle breeding, health care and veterinary services.

Fig. 5.13: A Dairy Farm in Austria

Fig. 5.14: Areas of Mixed Farming

It is highly labour intensive as it involves rigorous care in feeding and milching. There is no off season during the year as in the case of crop raising. It is practised mainly near urban and industrial centres which provide neighbourhood market for fresh milk and dairy products. The development of transportation, refrigeration, pasteurisation and other preservation processes have increased the duration of storage of various dairy products.

There are three main regions of commercial dairy farming. The largest is North Western Europe the second is Canada and the third belt includes South Eastern Australia, New Zealand and Tasmania (Fig. 5.16).

Fig. 5.15 (a): A vineyard in Switzerland

Fig. 5.15 (b): Collection of grapes in a collective farm of Kazakhstan

Mediterranean Agriculture Mediterranean agriculture is highly specialised commercial agriculture. It is practised in the countries on either side of the Mediterranean

Primary Activities

39

Fig. 5.16: Areas of Dairy Farming

sea in Europe and in north Africa from Tunisia to Atlantic coast, southern California, central Chile, south western parts of South Africa and south and south western parts of Australia. This region is an important supplier of citrus fruits. Viticulture or grape cultivation is a speciality of the Mediterranean region. Best quality wines in the world with distinctive flavours are produced from high quality grapes in various countries of this region. The inferior grapes are dried into raisins and currants. This region also produces olives and figs. The advantage of Mediterranean agriculture is that more valuable crops such as fruits and vegetables are grown in winters when there is great demand in European and North American markets. Market Gardening and Horticulture Market gardening and horticulture specialise in the cultivation of high value crops such as vegetables, fruits and flowers, solely for the urban markets. Farms are small and are located where there are good transportation 40

Fundamentals of Human Geography

links with the urban centre where high income group of consumers is located. It is both labour and capital intensive and lays emphasis on the use of irrigation, HYV seeds, fertilisers, insecticides, greenhouses and artificial heating in colder regions. This type of agriculture is well developed in densely populated industrial districts of north west Europe, north eastern United States of America and the Mediterranean regions. The Netherlands specialises in growing flowers and horticultural crops especially tulips, which are flown to all major cities of Europe. The regions where farmers specialise in vegetables only, the farming is know as truck farming. The distance of truck farms from the market is governed by the distance that a truck can cover overnight, hence the name truck farming. In addition to market gardening, a modern development in the industrial regions of Western Europe and North America is factory farming. Livestock, particularly poultry and cattle rearing, is done in stalls and pens, fed on manufactured feedstuff and carefully

Figure 5.17 (a): Vegetables being grown in the vicinity of the city

Figure 5.17 (b): Vegetables being loaded into a truck and cycle carts for transporting to city markets

supervised against diseases. This requires heavy capital investment in terms of building, machinery for various operations, veterinary services and heating and lighting. One of the important features of poultry farming and cattle rearing is breed selection and scientific breeding. Types of farming can also be categorised according to the farming organisation. Farming organisation is affected by the way in which farmers own their farms and various policies of the government which help to run these farms.

is based on social ownership of the means of production and collective labour. Collective farming or the model of Kolkhoz was introduced in erstwhile Soviet Union to improve upon the inefficiency of the previous methods of agriculture and to boost agricultural production for self-sufficiency. The farmers pool in all their resources like land, livestock and labour. However, they are allowed to retain very small plots to grow crops in order to meet their daily requirements. Yearly targets are set by the government and the produce is also sold to the state at fixed prices. Produce in excess of the fixed amount is distributed among the members or sold in the market. The farmers have to pay taxes on the farm produces, hired machinery etc. Members are paid according to the nature of the work allotted to them by the farm management. Exceptional work is rewarded in cash or kind. This type of farming was introduced in former Soviet Union under the socialist regime which was adopted by the socialist countries. After its collapse, these have already been modified.

Co-operative Farming A group of farmers form a co-operative society by pooling in their resources voluntarily for more efficient and profitable farming. Individual farms remain intact and farming is a matter of cooperative initiative. Co-operative societies help farmers, to procure all important inputs of farming, sell the products at the most favourable terms and help in processing of quality products at cheaper rates. Co-operative movement originated over a century ago and has been successful in many western European countries like Denmark, Netherlands, Belgium, Sweden, Italy etc. In Denmark, the movement has been so successful that practically every farmer is a member of a co-operative. Collective Farming The basic principal behind this types of farming

MINING The discovery of minerals in the history of human development, is reflected in many stages in terms of copper age, bronze age and iron age. The use of minerals in ancient times was largely confined to the making of tools, utensils and weapons. The actual development of mining began with the industrial revolution and its importance is continuously increasing. Primary Activities

41

as safety precautions and equipment is relatively low in this method. The output is both large and rapid. SHAFT MINING

OPEN-CAST OR (STRIP MINING)

Fig. 5.19: Methods of Mining

Fig. 5.18: Oil drilling operation in the Gulf of Mexico

Factors Affecting Mining Activity The profitability of mining operations thus, depends on two main factors: (i) Physical factors include the size, grade and the mode of occurrence of the deposits. (ii) Economic factors such as the demand for the mineral, technology available and used, capital to develop infrastructure and the labour and transport costs. Methods of Mining Depending on the mode of occurrence and the nature of the ore, mining is of two types: surface and underground mining. The surface mining also known as open-cast mining is the easiest and the cheapest way of mining minerals that occur close to the surface. Overhead costs such

42

Fundamentals of Human Geography

When the ore lies deep below the surface, underground mining method (shaft method) has to be used. In this method, vertical shafts have to be sunk, from where underground galleries radiate to reach the minerals. Minerals are extracted and transported to the surface through these passages. It requires specially designed lifts, drills, haulage vehicles, ventilation system for safety and efficient movement of people and material. This method is risky. Poisonous gases, fires, floods and caving in lead to fatal accidents. Have you ever read about mine fires and flooding of coal mines in India? The developed economies are retreating from mining, processing and refining stages of production due to high labour costs, while the developing countries with large labour force and striving for higher standard of living are becoming more important. Several countries of Africa and few of south America and Asia have over fifty per cent of the earnings from minerals alone.

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i)

(ii)

(iii)

(iv)

(v)

(vi)

(vii)

Which one of the following is not a plantation crop? (a) Coffee

(c)

Wheat

(b) Sugarcane

(d)

Rubber

In which one of the following countries co-operative farming was the most successful experiment? (a) Russia

(c)

India

(b) Denmark

(d)

The Netherlands

(a) Truck farming

(c)

Mixed farming

(b) Factory farming

(d)

Floriculture

Growing of flowers is called:

Which one of the following types of cultivation was developed by European colonists? (a) Kolkoz

(c)

Mixed farming

(b) Viticulture

(d)

Plantation

In which one of the following regions is extensive commercial grain cultivation not practised? (a) American Canadian prairies (c)

Pampas of Argentina

(b) European Steppes

Amazon Basin

(d)

In which of the following types of agriculture is the farming of citrus fruit very important? (a) Market gardening

(c)

Mediterranean agriculture

(b) Plantation agriculture

(d)

Co-operative farming

Which one type of agriculture amongst the following is also called ‘slash and burn agriculture’? (a) Extensive subsistence agriculture (b) Primitive subsistence agriculture (c)

Extensive commercial grain cultivation

(d) Mixed farming (viii)

2.

Which one of the following does not follow monoculture? (a) Dairy farming

(c)

Plantation agriculture

(b) Mixed farming

(d)

Commercial grain farming

Answer the following questions in about 30 words. (i) (ii) (iii)

Future of shifting cultivation is bleak. Discuss. Market gardening is practised near urban areas. Why? Large scale dairy farming is the result of the development of transportation and refrigeration.

Primary Activities

43

3.

Answer the following questions in not more than 150 words. (i) (ii)

Differentiate between Nomadic Herding and Commercial Livestock Rearing. Discuss the important characteristic features of plantation agriculture. Name a few important plantation crops from different countries.

Project/Activity Visit a nearby village and observe the cultivation of some crops. Ask the farmers and list the various operations.

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Fundamentals of Human Geography

Unit-III Chapter-6

Secondary Activities

All economic activities namely primary, secondary, tertiary and quaternary, revolve around obtaining and utilising resources necessary for survival. Secondary activities add value to natural resources by transforming raw materials into valuable products. Cotton in the boll has limited use but after it is transformed into yarn, becomes more valuable and can be used for making clothes. Iron ore, cannot be used; directly from the mines, but after being converted into steel it gets its value and can be used for making many valuable machines, tools, etc. The same is true of most of the materials from the farm, forest, mine and the sea. Secondary activities, therefore, are concerned with manufacturing, processing and construction (infrastructure) industries.

MANUFACTURING Manufacturing involves a full array of production from handicrafts to moulding iron and steel and stamping out plastic toys to assembling delicate computer components or space vehicles. In each of these processes, the common characteristics are the application of power, mass production of identical products and specialised labour in factory settings for the production of standardised commodities. Manufacturing may be done with modern power and machinery or it may still be very primitive. Most of the Third World countries still ‘manufacture’ in the literal sense of the term. It is difficult to present a full picture of all the manufacturers in these countries. More emphasis is given to the kind of ‘industrial’ activity which involves less complicated systems of production. Characteristics Manufacturing

of

Modern Large Scale

Modern large scale manufacturing has the following characteristics: Specialisation of Skills/Methods of Production Under the ‘craft’ method factories produce only a few pieces which are made-to-order. So the costs are high. On the other hand, mass

production involves production of large quantities of standardised parts by each worker performing only one task repeatedly.

‘Manufacturing’ Industry and ‘Manufacturing Industry’ Manufacturing literally means ‘to make by hand’. However, now it includes goods ‘made by machines’. It is essentially a process which involves transforming raw materials into finished goods of higher value for sale in local or distant markets. Conceptually, an industry is a geographically located manufacturing unit maintaining books of accounts and, records under a management system. As the term industry is comprehensive, it is also used as synonymous with ‘manufacturing’ When one uses terms like ‘steel industry’ and ‘chemical industry’ one thinks of factories and processes. But there are many secondary activities which are not carried on in factories such as what is now called the ‘entertainment industry’ and Tourism industry, etc. So for clarity the longer expression ‘manufacturing industry’ is used.

Mechanisation Mechanisation refers to using gadgets which accomplish tasks. Automation (without aid of human thinking during the manufacturing process) is the advanced stage of mechanisation. Automatic factories with feedback and closedloop computer control systems where machines are developed to ‘think’, have sprung up all over the world. Technological Innovation Technological innovations through research and development strategy are an important aspect of modern manufacturing for quality control, eliminating waste and inefficiency, and combating pollution. 46

Fundamentals of Human Geography

Organisational Structure and Stratification Modern manufacturing is characterised by: (i) a complex machine technology (ii) extreme specialisation and division of labour for producing more goods with less effort, and low costs (iii) vast capital (iv) large organisations (v) executive bureaucracy. Uneven Geographic Distribution Major concentrations of modern manufacturing have flourished in a few number of places. These cover less than 10 per cent of the world’s land area. These nations have become the centres of economic and political power. However, in terms of the total area covered, manufacturing sites are much less conspicuous and concentrated on much smaller areas than that of agriculture due to greater intensity of processes. For example, 2.5 sq km of the American corn belt usually includes about four large farms employing about 10-20 workers supporting 50-100 persons. But this same area could contain several large integrated factories and employ thousands of workers. Why do Large-scale Industries choose different locations?

Industries maximise profits by reducing costs. Therefore, industries should be located at points where the production costs are minimum. Some of the factors influencing industrial locations are as under: Access to Market The existence of a market for manufactured goods is the most important factor in the location of industries. ‘Market’ means people who have a demand for these goods and also have the purchasing power (ability to purchase) to be able to purchase from the sellers at a place. Remote areas inhabited by a few people offer small markets. The developed regions of Europe, North America, Japan and Australia provide large global markets as the purchasing power of the people is very high. The densely populated regions of South and South-east Asia also

provide large markets. Some industries, such as aircraft manufacturing, have a global market. The arms industry also has global markets.

Communication is also an important need for industries for the exchange and management of information.

Access to Raw Material

Government Policy

Raw material used by industries should be cheap and easy to transport. Industries based on cheap, bulky and weight-losing material (ores) are located close to the sources of raw material such as steel, sugar, and cement industries. Perishability is a vital factor for the industry to be located closer to the source of the raw material. Agro-processing and dairy products are processed close to the sources of farm produce or milk supply respectively.

Governments adopt ‘regional policies’ to promote ‘balanced’ economic development and hence set up industries in particular areas.

Access to Labour Supply Labour supply is an important factor in the location of industries. Some types of manufacturing still require skilled labour. Increasing mechanisation, automation and flexibility of industrial processes have reduced the dependence of industry upon the labours. Access to Sources of Energy Industries which use more power are located close to the source of the energy supply such as the aluminium industry. Earlier coal was the main source of energy, today hydroelectricity and petroleum are also important sources of energy for many industries. Access to Transportation and Communication Facilities Speedy and efficient transport facilities to carry raw materials to the factory and to move finished goods to the market are essential for the development of industries. The cost of transport plays an important role in the location of industrial units. Western Europe and eastern North America have a highly developed transport system which has always induced the concentration of industries in these areas. Modern industry is inseparably tied to transportation systems. Improvements in transportation led to integrated economic development and regional specialisation of manufacturing.

Access to Agglomeration Economies/ Links between Industries Many industries benefit from nearness to a leader-industry and other industries. These benefits are termed as agglomeration economies. Savings are derived from the linkages which exist between different industries. These factors operate together to determine industrial location.

Foot Loose Industries Foot loose industries can be located in a wide variety of places. They are not dependent on any specific raw material, weight losing or otherwise. They largely depend on component parts which can be obtained anywhere. They produce in small quantity and also employ a small labour force. These are generally not polluting industries. The important factor in their location is accessibility by road network.

Classification of Manufacturing Industries Manufacturing industries are classified on the basis of their size, inputs/raw materials, output/products and ownership (Fig. 6.1). Industries based on Size The amount of capital invested, number of workers employed and volume of production determine the size of industry. Accordingly, industries may be classified into household or cottage, small-scale and large-scale. Secondary Activities

47

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Fundamentals of Human Geography

Artifacts

Cottage or Household

Small Scale

Size

Mineral based

Non-ferrous

Copper, aluminium, gems and jewellery

Iron and Steel

Metallic

Sugar, edible oil, cotton textile, coffee, tea, rubber, etc.

Agro based

Ferrous

Large Scale

Timber, lac, terpentine, paper

Forest based

Leather, wool

Animal based

Biscuits

Iron and Steel

Textiles

Consumer goods

Output/Product

Basic

Fig. 6.1 : Classification of Industries

Cement, Pottery

Non-Metallic

Petrochemical, plastic, synthetic, fibre, salts, chemicals fertilisers

Chemical based

Inputs/Raw Materials

Based on

Classification of Industries

Vehicles, e.g. cars, scooters, cycles

Public Sector

Private Sector

Size

Joint Sector

HOUSEHOLD INDUSTRIES OR COTTAGE MANUFACTURING It is the smallest manufacturing unit. The craftsmen or artisans use local raw materials and simple hand tools to produce everyday goods in their homes with the help of their family members or part-time labour. Finished products may be for consumption in the same household or, for sale in local (village) markets, or, for barter. Capital and transportation do not wield much influence as this type of manufacturing has low commercial significance and most of the tools are devised locally.

Some common everyday products produced in this sector of manufacturing include foodstuffs, fabrics, mats, containers, tools, furniture, shoes, and figurines from wood lot and forest, shoes, thongs and other articles from leather; pottery and bricks from clays and stones. Goldsmiths make jewellery of gold, silver and bronze. Some artefacts and crafts are made out of bamboo, wood obtained locally from the forests. Small Scale Manufacturing Small scale manufacturing is distinguished from household industries by its production techniques and place of manufacture (a workshop outside the home/cottage of the producer). This type of manufacturing uses local raw material, simple power -driven machines and semi-skilled labour. It provides employment and raises local purchasing power. Therefore, countries like India, China, Indonesia and Brazil, etc. have developed labour-intensive small scale manufacturing in order to provide employment to their population.

Fig. 6.2 (a) : A man making pots in his courtyardexample of household industry in Nagaland

Fig. 6.3: Products of Cottage Industry on Sale in Assam

Large Scale Manufacturing

Fig. 6.2 (b) : A man weaving a bamboo basket by the roadside in Arunachal Pradesh

Large scale manufacturing involves a large market, various raw materials, enormous energy, specialised workers, advanced technology, assembly-line mass production and large capital. This kind of manufacturing developed in the last 200 years, in the United Kingdom, north-eastern U.S.A. and Europe. Now it has diffused in almost all over the world. Secondary Activities

49

On the basis of the system of large scale manufacturing, the world’s major industrial regions may be grouped under two broad types, namely (i) traditional large-scale industrial regions which are thickly clustered in a few more developed countries. (ii) high-technology large scale industrial regions which have diffused to less developed countries.

Fig. 6.5: Tea Garden and a Tea Factory in the Nilgiri Hills of Tamil Nadu

Agri-business is commercial farming on an industrial scale often financed by business whose main interests lie outside agriculture, for example, large corporations in tea plantation business. Agri-business farms are mechanised, large in size, highly structured, reliant on chemicals, and may be described as ‘agro-factories’.

Fig. 6.4 : Passenger car assembly hires at a plant of the Motor Company in Japan

Industries based on Inputs/Raw Materials On the basis of the raw materials used, the industries are classified as: (a) agro-based; (b) mineral based; (c) chemical based; (d) forest based: and (e) animal based. (a)

Agro based Industries

Agro processing involves the processing of raw materials from the field and the farm into finished products for rural and urban markets. Major agro-processing industries are food processing, sugar, pickles, fruits juices, beverages (tea, coffee and cocoa), spices and oils fats and textiles (cotton, jute, silk), rubber, etc. Food Processing Agro processing includes canning, producing cream, fruit processing and confectionery. While some preserving techniques, such as drying, fermenting and pickling, have been known since ancient times, these had limited applications to cater to the pre-Industrial Revolution demands. 50

Fundamentals of Human Geography

(b)

Mineral based Industries

These industries use minerals as a raw material. Some industries use ferrous metallic minerals which contain ferrous (iron), such as iron and steel industries but some use non-ferrous metallic minerals, such as aluminium, copper and jewellery industries. Many industries use non-metallic minerals such as cement and pottery industries. (c)

Chemical based Industries

Such industries use natural chemical minerals, e.g. mineral-oil (petroleum) is used in petrochemical industry. Salts, sulphur and potash industries also use natural minerals. Chemical industries are also based on raw materials obtained from wood and coal. Synthetic fibre, plastic, etc. are other examples of chemical based industries.

(d)

Forest based Raw Material using Industries

The forests provide many major and minor products which are used as raw material. Timber for furniture industry, wood, bamboo and grass for paper industry, lac for lac industries come from forests.

INDUSTRIES BASED ON OWNERSHIP (a) Public Sector Industries are owned and managed by governments. In India, there were a number of Public Sector Undertakings (PSUs). Socialist countries have many state owned industries. Mixed economies have both Public and Private sector enterprises. (b) Private Sector Industries are owned by individual investors. These are managed by private organisations. In capitalist countries, industries are generally owned privately. (c) Joint Sector Industries are managed by joint stock companies or sometimes the private and public sectors together establish and manage the industries. Can you make a list of such industries? Traditional Large-Scale Industrial Regions

Fig. 6.6: A pulp mill in the heart of the Ketchikan’s timber area of Alaska

(e)

Animal based Industries

Leather for leather industry and wool for woollen textiles are obtained from animals. Besides, ivory is also obtained from elephant’s tusks. Industries Based On Output/Product You have seen some machines and tools made of iron or steel. The raw material for such machines and tools is iron and steel. Which is itself an industry. The industry whose products are used to make other goods by using them as raw materials are basic industries. Can you machines identify the links? Iron/steel clothes for use by for textile industry consumers. The consumer goods industries produced goods which are consumed by consumers directly. For example, industries producing breads and biscuits, tea, soaps and toiletries, paper for writing, televisions, etc. are consumer goods or non-basic industries.

These are based on heavy industry, often located near coal-fields and engaged in metal smelting, heavy engineering, chemical manufacture or textile production. These industries are now known as smokestack industries. Traditional industrial regions can be recognised by: • High proportion of employment in manufacturing industry. High-density housing, often of inferior type, and poor services. Unattractive environment, for example, pollution, waste heaps, and so on. • Problems of unemployment, emigration and derelict land areas caused by closure of factories because of a worldwide fall in demand. The Ruhr Coal-field, Germany This has been one of the major industrial regions of Europe for a long time. Coal and iron and steel formed the basis of the economy, but as the demand for coal declined, the industry started shrinking. Even after the iron ore was exhausted, the industry remained, using imported ore brought by waterways to the Ruhr. The Ruhr region is responsible for 80 per cent of Germany’s total steel production. Secondary Activities

51

Changes in the industrial structure have led to the decay of some areas, and there are problems of industrial waste and pollution. The future prosperity of the Ruhr is based less on the products of coal and steel, for which it was initially famous, and more on the new industries like the huge Opel car assembly plant, new chemical plants, universities. Outof-town shopping centres have appeared resulting in a ‘New Ruhr’ landscape. Concept of High Technology Industry High technology, or simply high-tech, is the latest generation of manufacturing activities. It is best understood as the application of intensive research and development (R and D) efforts leading to the manufacture of products of an advanced scientific and engineering character. Professional (white collar) workers make up a large share of the total workforce. These highly skilled specialists greatly outnumber the actual production (blue collar) workers. Robotics on the assembly line, computer -aided design (CAD) and manufacturing, electronic controls of smelting and refining processes, and the constant development of new chemical and pharmaceutical products are notable examples of a high-tech industry. Neatly spaced, low, modern, dispersed, office-plant-lab buildings rather than massive assembly structures, factories and storage areas mark the high-tech industrial landscape. Planned business parks for high-tech start-ups have become part of regional and local development schemes. High-tech industries which are regionally concentrated, self-sustained and highly specialised are called technopolies. The Silicon Valley near San Francisco and Silicon Forest near Seattle are examples of technopolies. Are some technopolies developing in India? Manufacturing contributes significantly to the world economy. Iron and steel, textiles, automobiles, petrochemicals and electronics are some of the world’s most important manufacturing industries.

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Fundamentals of Human Geography

Iron and Steel Industry The iron and steel industry forms the base of all other industries and, therefore, it is called a basic industry. It is basic because it provides raw material for other industries such as machine tools used for further production. It may also be called a heavy industry because it uses large quantities of bulky raw materials and its products are also heavy. Iron is extracted from iron ore by smelting in a blast furnace with carbon (coke) and limestone. The molten iron is cooled and moulded to form pig iron which is used for converting into steel by adding strengthening materials like manganese. The large integrated steel industry is traditionally located close to the sources of raw materials – iron ore, coal, manganese and limestone – or at places where these could be easily brought, e.g. near ports. But in mini steel mills access to markets is more important than inputs. These are less expensive to build and operate and can be located near markets because of the abundance of scrap metal, which is the main input. Traditionally, most of the steel was produced at large integrated plants, but mini mills are limited to just one-step process – steel making – and are gaining ground. Distribution : The industry is one of the most complex and capital-intensive industries and is concentrated in the advanced countries of North America, Europe and Asia. In U.S.A, most of the production comes from the north Appalachian region (Pittsburgh), Great Lake region (Chicago-Gary, Erie, Cleveland, Lorain, Buffalo and Duluth) and the Atlantic Coast (Sparrows Point and Morisville). The industry has also moved towards the southern state of Alabama. Pittsburg area is now losing ground. It has now become the “rust bowl” of U.S.A. In Europe, U.K., Germany, France, Belgium, Luxembourgh, the Netherlands and Russia are the leading producers. The important steel centres are Birmingham and Sheffield in the U.K.; Duisburg, Dortmund, Dusseldorf and Essen in Germany; Le Creusot and St. Ettienne in France; and Moscow, St. Petersburgh, Lipetsk, Tula, in Russia and Krivoi Rog, and

Donetsk in Ukraine. In Asia, the important centres include Nagasaki and Tokyo-Yokohama in Japan; Shanghai, Tienstin and Wuhan in China; and Jamshedpur, Kulti-Burnpur, Durgapur, Rourkela, Bhilai, Bokaro, Salem, Visakhapatnam and Bhadravati in India. Consult your atlas to locate these places/ centres. Cotton Textile Industry Cotton textile industry has three sub-sectors i.e. handloom, powerloom and mill sectors. Handloom sector is labour -intensive and provides employment to semi-skilled workers. It requires small capital investment. Why did Mahatma Gandhi propagate Khadi as part of the independence movement? This sector involves spinning, weaving and finishing of the fabrics. The powerloom sector introduces machines and becomes less labour intensive

and the volume of production increases. Cotton textile mill sector is highly capital intensive and produces fine clothes in bulk. Cotton textile manufacturing requires good quality cotton as raw material. India, China, U.S.A, Pakistan, Uzbekistan, Egypt produce more than half of the world’s raw cotton. The U.K, NW European countries and Japan also produce cotton textile made from imported yarn. Europe alone accounts for nearly half of the world’s cotton imports. The industry has to face very stiff competition with synthetic fibres hence it has now shown a declining trend in many countries. With the scientific advancement and technological improvements the structure of industries changes. For example, Germany recorded constant growth in cotton textile industry since Second World War till the seventies but now it has declined. It has shifted to less developed countries where labour costs are low.

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i)

Which one of the following statements is wrong? (a) Cheap water transport has facilitated the jute mill industry along the Hugli. (b) Sugar, cotton textiles and vegetable oils are footloose industries. (c)

The development of hydro-electricity and petroleum reduced, to a great extent, the importance of coal energy as a locational factor for industry.

(d) Port towns in India have attracted industries. (ii)

(iii)

In which one of the following types of economy are the factors of production owned individually ? (a) Capitalist

(c)

(b) Mixed

(d) None

Socialist

Which one of the following types of industries produces raw materials for other industries? (a) Cottage Industries

(c)

Basic Industries

(b) Small-scale Industries

(d) Footloose Industries Secondary Activities

53

(iv)

Which one of the following pairs is correctly matched ? (a)

2.

… Los Angeles

(b)

Shipbuilding industry

… Lusaka

(c)

Aircraft industry

… Florence

(d)

Iron and Steel industry

… Pittsburgh

Write a short note on the following in about 30 words. (i) (ii) (iii)

3.

Automobile industry

High-Tech industry Manufacturing Footloose industries

Answer the following in not more than 150 words. (i)

Differentiate between primary and secondary activities.

(ii)

Discuss the major trends of modern industrial activities especially in the developed countries of the world.

(iii)

Explain why high-tech industries in many countries are being attracted to the peripheral areas of major metropolitan centres.

(iv)

Africa has immense natural resources and yet it is industrially the most backward continent. Comment.

Project/Activity (i) (ii) (iii)

54

Carry out a survey in your school premises of the factory-made goods used by students and the staff. Find out the meaning of the terms bio-degradable and nonbiodegradable. Which kind of material is better to use? Why? Look around and make a list of the global brands, their logos and products.

Fundamentals of Human Geography

Unit-III Chapter-7

Tertiary and Quaternary Activities

When you fall ill you go to your family doctor or you call a doctor. Sometimes your parents take you to a hospital for treatment. While in school, you are taught by your teachers. In the event of any dispute, legal opinion is obtained from a lawyer. Likewise, there are many professionals who provide their services against payment of their fee. Thus, all types of services are special skills provided in exchange of payments. Health, education, law, governance and recreation etc. require professional skills. These services require other theoretical knowledge and practical training. Tertiary activities are related to the service sector. Manpower is an important component of the service sector as most of the tertiary activities are performed by skilled labour, professionally trained experts and consultants. In the initial stages of economic development, larger proportion of people worked in the primary sector. In a developed economy, the majority of workers get employment in tertiary activity and a moderate proportion is employed in the secondary sector. Tertiary activities include both production and exchange. The production involves the ‘provision’ of services that are ‘consumed’. The output is indirectly measured in terms of wages and salaries. Exchange, involves trade, transport and communication facilities that are used to overcome distance. Tertiary activities, therefore, involve the commercial output of services rather than the production of tangible goods. They are not directly involved in the processing of physical raw materials. Common examples are the work of a plumber, electrician, technician, launderer, barber, shopkeeper, driver, cashier, teacher, doctor, lawyer and publisher etc. The main difference between secondary activities and tertiary activities is that the expertise provided by services relies more heavily on specialised skills, experience and knowledge of the workers rather than on the production techniques, machinery and factory processes.

TYPES OF TER TIAR Y ACTIVITIES TERTIAR TIARY By now you know that you purchase your books, stationery from traders shop, travel by

Fig. 7.1: Service Sector

56

Fundamentals of Human Geography

bus or rail, send letters, talk on telephone and obtain services of teachers for studies and doctors at the time of illness. Thus, trade, transport, communication and services are some of the tertiary activities discussed in this section. The chart provides the basis for classifying the tertiary activities.

TRADE AND COMMERCE Trade is essentially buying and selling of items produced elsewhere. All the services in retail and wholesale trading or commerce are specifically intended for profit. All this work takes place in towns and cities also known as trading centres. The rise of trading from barter at the local level to money-exchange of international scale has produced many centres and institutions such as trading centres or collection and distribution points. Trading centres may be divided into rural and urban marketing centres. Rural marketing centres cater to nearby settlements. These are quasi-urban centres. They serve as trading centres of the most rudimentary type. Here personal and professional services are not well-developed. These form local collecting and distributing centres. Most of these have mandis (wholesale markets) and also retailing areas. They are not urban centres per se but are significant centres for making available goods and services which are most frequently demanded by rural folk.

Periodic markets in rural areas are found where there are no regular markets and local periodic markets are organised at different temporal intervals. These may be weekly, biweekly markets from where people from the surrounding areas meet their temporally accumulated demand. These markets are held on specified dates and move from one place to another. The shopkeepers thus, remain busy on all the days while a large area is served by them. Urban marketing centres have more widely specialised urban services. They provide ordinary goods and services as well as many of the specialised goods and services required by people. Urban centres, therefore, offer manufactured goods as well as many specialised markets develop, e.g. markets for labour, housing, semi or finished products. Services of educational institutions and professionals such as teachers, lawyers, consultants, physicians, dentists and veterinary doctors are available.

Fig. 7.3: Packed Food Market in U.S.A.

RET AIL TRADING SER VICES RETAIL SERVICES

Fig. 7.2: A Wholesale Vegetable Market

This is the business activity concerned with the sale of goods directly to the consumers. Most of the retail trading take place in fixed establishments or stores solely devoted to selling. Street peddling, handcarts, trucks, door-to-door, mail-order, telephone, automatic vending machines and internet are examples of non-store retail selling. Tertiary and Quaternary Activities

57

More on Stores Consumer cooperatives were the first of the large-scale innovations in retailing. Departmental stores delegate the responsibility and authority to departmental heads for purchasing of commodities and for overseeing the sale in different sections of the stores. Chain stores are able to purchase merchandise most economically, often going so far as to direct the goods to be manufactured to their specification. They employ highly skilled specialists in many executive tasks. They have the ability to experiment in one store and apply the results to many.

particular route; and cost distance or the expense of travelling on a route. In selecting the mode of transport, distance, in terms of time or cost, is the determining factor. Isochrone lines are drawn on a map to joins places equal in terms of the time taken to reach them.

Network and Accessibility As transport systems develop, different places are linked together to form a network. Networks are made up of nodes and links. A node or vertex, is the meeting point of two or more routes, a point of origin, a point of destination or any sizeable town along a route, Every road that joins two nodes is called a link or edge. A developed network has many links, which means that places are well-connected.

WHOLESALE TRADING SERVICE

Factors Affecting Transport Services

Wholesale trading constitutes bulk business through numerous intermediary merchants and supply houses and not through retail stores. Some large stores including chain stores are able to buy directly from the manufacturers. However, most retail stores procure supplies from an intermediary source. Wholesalers often extend credit to retail stores to such an extent that the retailer operates very largely on the wholesaler’s capital.

Demand for transport is influenced by the size of population. The larger the population size, the greater is the demand for transport. Routes depend on: location of cities, towns, villages, industrial centres and raw materials, pattern of trade between them, nature of the landscape between them, type of climate, and funds available for overcoming obstacles along the length of the route.

COMMUNICATION SERVICES TRANSPOR T AND COMMUNICA TION TRANSPORT COMMUNICATION Communication services involve the SERVICES transmission of words and messages, facts Transport is a service or facility by which persons, manufactured goods, and property are physically carried from one location to another. It is an organised industry created to satisfy man’s basic need of mobility. Modern society requires speedy and efficient transport systems to assist in the production, distribution and consumption of goods. At every stage in this complex system, the value of the material is significantly enhanced by transportation. Transport distance can be measured as: km distance or actual distance of route length; time distance or the time taken to travel on a 58

Fundamentals of Human Geography

and ideas. The invention of writing preserved messages and helped to make communication dependent on means of transport. These were actually carried by hand, animals, boat, road, rail and air. That is why all forms of transport are also referred to as lines of communication. Where the transport network is efficient, communications are easily disseminated. Certain developments, such as mobile telephony and satellites, have made communications independent of transport. All forms are not fully disassociated because of the cheapness of the older systems. Thus, very

large volumes of mail continue to be handled by post offices all over the world. Some of the communication services are discussed below. Telecommunications The use of telecommunications is linked to the development of electrical technology. It has revolutionised communications because of the speed with which messages are sent. The time reduced is from weeks to minutes and recent advancements like mobile telephony have made communications direct and instantaneous at any time and from anywhere. The telegraph, morse code and telex have almost become things of the past. Radio and television also help to relay news, pictures, and telephone calls to vast audiences around the world and hence they are termed as mass media. They are vital for advertising and entertainment. Newspapers are able to cover events in all corners of the world. Satellite communication relays information of the earth and from space. The internet has truly revolutionised the global communication system .

legislation have established corporations to supervise and control the marketing of such services as transport, telecommunication, energy and water supply. Professional services are primarily health care, engineering, law and management. The location of recreational and entertainment services depends on the market. Multiplexes and restaurants might find location within or near the Central Business District (CBD), whereas a golf course would choose a site where land costs are lower than in the CBD. Informal/Non-Formal Sector Personal services are made available to the people to facilitate their work in daily life. The workers migrate from rural areas in search of employment and are unskilled. They are employed in domestic services as housekeepers, cooks, and gardeners. This segment of workers is unorganised. One such example in India is Mumbai’s dabbawala (Tiffin) service provided to about 1,75,000 customers all over the city.

SERVICES Services occur at many different levels. Some are geared to industry, some to people; and some to both industry and people, e.g. the transport systems. Low-order services, such as grocery shops and laundries, are more common and widespread than high-order services or more specialised ones like those of accountants, consultants and physicians. Services are provided to individual consumers who can afford to pay for them. For example the gardener, the launderers and the barber do primarily physical labour. Teacher, lawyers, physicians, musicians and others perform mental labour. Many services have now been regulated. Making and maintaining highways and bridges, maintaining fire fighting departments and supplying or supervising education and customer -care are among the important services most often supervised or performed by governments or companies. State and union

Fig. 7.4: Dabbawala Service in Mumbai

PEOPLE ENG AGED IN ENGA TER TIAR Y ACTIVITIES TERTIAR TIARY Today most people are service workers. Services are provided in all societies. But in more developed countries a higher percentage of workers is employed in provision of services in contrast to less than 10 per cent in the less developed countries. In U.S.A. over 75 per cent of workers are engaged in services. The trend Tertiary and Quaternary Activities

59

in employment in this sector has been increasing while it has remained unchanged or decreasing in the primary and secondary activities. Some Selected Examples Tourism Tourism is travel undertaken for purposes of recreation rather than business. It has become the world’s single largest tertiary activity in total registered jobs (250 million) and total revenue (40 per cent of the total GDP). Besides, many local persons, are employed to provide services like accommodation, meals, transport, entertainment and special shops serving the tourists. Tourism fosters the growth of infrastructure industries, retail trading, and craft industries (souvenirs). In some regions, tourism is seasonal because the vacation period is dependent on favourable weather conditions, but many regions attract visitors all the year round.

Fig. 7.5: Tourists skiing in the snow capped mountain slopes of Switzerland

Tourist Regions The warmer places around the Mediterranean Coast and the West Coast of India are some of the popular tourist destinations in the world. Others include winter sports regions, found mainly in mountainous areas, and various scenic landscapes and national parks, which are scattered. Historic towns also attract 60

Fundamentals of Human Geography

tourists, because of the monument, heritage sites and cultural activities. Factors Affecting Tourism Demand : Since the last century, the demand for holidays has increased rapidly. Improvements in the standard of living and increased leisure time, permit many more people to go on holidays for leisure. Transport : The opening-up of tourist areas has been aided by improvement in transport facilities. Travel is easier by car, with better road systems. More significant in recent years has been the expansion in air transport. For example, air travel allows one to travel anywhere in the world in a few hours of flyingtime from their homes. The advent of package holidays has reduced the costs. Tourist Attractions Climate: Most people from colder regions expect to have warm, sunny weather for beach holidays. This is one of the main reasons for the importance of tourism in Southern Europe and the Mediterranean lands. The Mediterranean climate offers almost consistently higher temperatures, than in other parts of Europe, long hours of sunshine and low rainfall throughout the peak holiday season. People taking winter holidays have specific climatic requirements, either higher temperatures than their own homelands, or snow cover suitable for skiing. Landscape: Many people like to spend their holidays in an attractive environment, which often means mountains, lakes, spectacular sea coasts and landscapes not completely altered by man. History and Art: The history and art of an area have potential attractiveness. People visit ancient or picturesque towns and archaeological sites, and enjoy exploring castles, palaces and churches. Culture and Economy: These attract tourists with a penchant for experiencing ethnic and local customs. Besides, if a region provides for the needs of tourists at a cheap cost, it is likely to become very popular. Home-stay has emerged as a profitable business such as

heritage homes in Goa, Madikere and Coorg in Karnataka. Empowered Workers Entrepreneurs are the empowered workers of the quarternary sector and the slowly emerging quinrary sector. They represent an important stage of development in the hierarchy of economic activity where the need for selfactualisation is not motivated by wealth and security alone but by other factors. They have predominantly a value system which emphasises quality of life and believe in creativity and individual values.

The illiterate of the twenty first century will not be those who do not read or write but those who do not learn, re-learn and un-learn. –Alvin Toffler

Where Will it All Lead to?

No one can be sure where all this change will lead to but some patterns do point strongly to the future. As ideas and freedom of information and communication grow, people will expect their applications at the workplace. More employees will receive training and become highly skilled. They will work more and more on their own initiative. Many will have flexible working arrangements. Some will choose work – paid and unpaid – that is personally fulfilling and accords with their concern for natural environment and social issues. These are just predictions. But part of the future belongs to you. By the choices made, you, too, can affect the changing patterns and work without increasing the strain upon natural resources and help save the planet.

QU ATERN AR Y ACTIVITIES QUA TERNAR ARY What do a CEO of an MNC in Copenhagen, at New York and a medical transcriptionist at Bangalore have in common? All these people work in a segment of the service sector that is knowledge oriented. This sector can be divided into quaternary and quinary activities. Quaternary activities involve some of the following: the collection, production and dissemination of information or even the production of information. Quaternary activities centre around research, development and may be seen as an advanced form of services involving specialised knowledge, technical skills, and administrative competence.

The Quaternary Sector The Quaternary Sector along with the Tertiary Sector has replaced all primary and secondary employment as the basis for economic growth. Over half of all workers In developed economies are in the ‘Knowledge Sector’ and there has been a very high growth in demand for and consumption of information-based services Tertiary and Quaternary Activities

61

from mutual fund managers to tax consultants, software developers and statisticians. Personnel working in office buildings, elementary schools and university classrooms, hospitals and doctors’ offices, theatres, accounting and brokerage firms all belong to this category of services. Like some of the tertiary functions, quaternary activities can also be outsourced. They are not tied to resources, affected by the environment, or necessarily localised by market.

QUIN AR Y ACTIVITIES QUINAR ARY The highest level of decision makers or policy makers perform quinary activities. These are subtly different from the knowledge based industries that the quinary sector in general deals with.

Quinary activities are services that focus on the creation, re-arrangement and interpretation of new and existing ideas; data interpretation and the use and evaluation of new technologies. Often referred to as ‘gold collar’ professions, they represent another subdivision of the tertiary sector representing special and highly paid skills of senior business executives, government officials, research scientists, financial and legal consultants, etc. Their importance in the structure of advanced economies far outweighs their numbers.

Outsourcing has resulted in the opening up of a large number of call centres in India, China, Eastern Europe, Israel, Philippines and Costa Rica. It has created new jobs in these countries. Outsourcing is coming to those countries where cheap and skilled workers are available. These are also out-migrating countries. With the work available though outsourcing, the migration in these countries

62

Fundamentals of Human Geography

may come down. Outsourcing countries are facing resistance from job-seeking youths in their respective countries. The comparative advantage is the main reason for continuing outsourcing. New trends in quarternary services include knowledge processing outsourcing (KPO) and ‘home shoring’, the latter as an alternative to outsourcing. The KPO industry is distinct from Business Process Outsourcing (BPO) as it involves more high skilled workers. It is information driven knowledge outsourcing. KPO enables companies to create additional business opportunities. Examples of KPOs include research and development (R and D) activities, e-learning, business research, intellectual property (IP) research, legal profession and the banking sector.

Outsourcing Outsourcing or contracting out is giving work to an outside agency to improve efficiency and reduce costs. When outsourcing involves transferring work to overseas locations, it is described by the term off shoring, although both off - shoring and outsourcing are used together. Business activities that are outsourced include information technology (IT), human resources, customer support and call centre services and at times also manufacturing and engineering. Data processing is an IT related service easily be carried out in Asian, East European and African countries, In these countries IT skilled staff with good English language skills are available at lower wages than those in the developed countries. Thus, a company in Hyderabad or Manila does work on a project based on GIS techniques for a country like U.S.A or Japan. Overhead costs are also much lower making it profitable to get job-work carried out overseas, whether it is in India, China or even a less populous country like Botswana in Africa.

Describe the nature of work against each colour-name

Colour of the collar Nature of work Red Gold White Grey Blue Pink

? ? ? ? ? ?

Medical Services for Overseas Patients in India About 55,000 patients from U.S.A. visited India in 2005 for treatment. This is still a small number compared with the millions of surgeries performed each year in the U.S. healthcare system. India has emerged as the leading country of medical tourism in the world. World class hospitals located in metropolitan cities cater to patients all over the world. Medical tourism brings abundant benefits to developing countries like India, Thailand, Singapore and Malaysia. Beyond medical tourism, is the trend of outsourcing of medical tests and data interpretation. Hospitals in India, Switzerland and Australia have been performing certain medical services – ranging from reading radiology images, to interpreting Magnetic Resonance Images (MRIs) and ultrasound tests.

Outsourcing holds tremendous advantages for patients, if it is focused on improving quality or providing specialised care.

Medical Tourism When medical treatment is combined with international tourism activity, it lends itself to what is commonly known as medical tourism.

THE DIGIT AL DIVIDE DIGITAL Opportunities emerging from the Information and Communication Technology based development is unevenly distributed across the globe. There are wide ranging economic, political and social differences among countries. How quickly countries can provide ICT access and benefits to its citizens is the deciding factor. While developed countries in general have surged forward, the developing countries have lagged behind and this is known as the digital divide. Similarly digital divides exist within countries. For example, in a large country like India or Russia, it is inevitable that certain areas like metropolitan centres possess better connectivity and access to the digital world versus peripheral rural areas.

Organise an informal debate session in your class about how could the emerging medical industry of our country become a boom as well as doom? Tertiary and Quaternary Activities

63

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i)

(ii)

(iii)

(iv)

(v)

Which one of the following is a tertiary activity? (a) Farming

(c)

Weaving

(b) Trading

(d)

Hunting

Which one of the following activities is NOT a secondary sector activity? (a) Iron Smelting

(c)

Making garments

(b) Catching fish

(d)

Basket Weaving

Which one of the following sectors provides most of the employment in Delhi, Mumbai, Chennai and Kolkata. (a) Primary

(c)

Secondary

(b) Quaternary

(d)

Service

Jobs that involve high degrees and level of innovations are known as: (a) Secondary activities

(c)

Quinary activities

(b) Quaternary activities

(d)

Primary activities

Which one of the following activities is related to quaternary sector? (a) Manufacturing computers

(c) University teaching

(b) Paper and Raw pulp production (d) Printing books (vi)

Which one out of the following statements is not true? (a) Outsourcing reduces costs and increases efficiency. (b) At times engineering and manufacturing jobs can also be outsourced. (c)

BPOs have better business opportunities as compared to KPOs.

(d) There may be dissatisfaction among job seekers in the countries that outsource the job. 2.

3.

Answer the following questions in about 30 words. (i)

Explain retail trading service.

(ii)

Describe quaternary services.

(iii)

Name the fast emerging countries of medical tourism in the world.

(iv)

What is digital divide?

Answer the following questions in not more than 150 words. (i) (ii)

Discuss the significance and growth of the service sector in modern economic development. Explain in detail the significance of transport and communication services.

Project/Activity (i) (ii)

64

Find out the activities of BPO. Find out from a travel agent the documents you need to travel abroad.

Fundamentals of Human Geography

Unit-III Chapter-8

Transport and Communication

Natural resources, economic activities and markets are rarely found in one place. Transport, communication and trade establish links between producing centres and consuming centres. The system of mass production and exchange is complex. Each region produces the items for which it is best suited. T rade or the exchange of such commodities relies on transportation and communication. Likewise, the high living standards and quality of life depend on efficient transportation, communications and trade. In earlier days, the means of transport and communication were the same. But today both have acquired distinct and specialised forms. Transport provides the network of links and carriers through which trade takes place.

TRANSPOR T TRANSPORT Transport is a service or facility for the carriage of persons and goods from one place to the other using humans, animals and different kinds of vehicles. Such movements take place over land, water and air. Roads and railways form part of land transport; while shipping and waterways and airways are the other two modes. Pipelines carry materials like petroleum, natural gas, and ores in liquidified form. Moreover, transportation is an organised service industry created to satisfy the basic needs of society. It includes transport arteries, vehicles to carry people and goods, and the organisation to maintain arteries, and to handle loading, unloading and delivery. Every nation has developed various kinds of transportation for defence purposes. Assured and speedy transportation, along with efficient communication, promote cooperation and unity among scattered peoples.

What is a Transport Network ? Several places (nodes) joined together by a series of routes (links) to form a pattern.

MODES OF TRANSPOR TATION TRANSPORT The principal modes of world transportation, as already mentioned are land, water, air and

pipelines. These are used for inter-regional and intra-regional transport, and each one (except pipelines) carries both passengers and freight. The significance of a mode depends on the type of goods and services to be transported, costs of transport and the mode available. International movement of goods is handled by ocean freighters. Road transport is cheaper and faster over short distances and for door-todoor services. Railways are most suited for large volumes of bulky materials over long distances within a country. High-value, light and perishable goods are best moved by airways. In a well-managed transport system, these various modes complement each other.

Land Transport Most of the movement of goods and services takes place over land. In early days, humans themselves were carriers. Have you ever seen a bride being carried on a palanquin (palki/doli) by four persons (Kahars in north India). Later animals were used as beasts of burden. Have you seen mules, horses and camels, carrying loads of cargo in rural areas? With the invention of the wheel, the use of carts and wagons became important. The revolution in transport came about only after the invention of the steam engine in the eighteenth century. Perhaps the first public railway line was opened in 1825 between Stockton and Darlington in northern England and then onwards, railways became the most popular and fastest form of transport in the nineteenth century. It opened up continental interiors for commercial grain farming, mining and manufacturing in U.S.A. The invention of the internal combustion engine revolutionised road transport in terms of road quality and vehicles (motor cars and trucks) plying over them. Among the newer developments in land transportation are pipelines, ropeways and cableways. Liquids like mineral oil, water, sludge and sewers are transported by pipelines. The great freight carriers are the railways, ocean vessels, barges, boats and motor trucks and pipelines. In general, the old and elementary forms like the human porter, pack animal, cart or wagon are the most expensive means of 66

Fundamentals of Human Geography

Fig. 8.1: Ropeway and Cable cars in Austria

This means of transport is usually found on steep mountain slopes and mines which are not suitable for building roads.

transportation and large freighters are the cheapest. They are important in supplementing modern channels and carriers which penetrate the interiors in large countries. In the densely populated districts of India and China, overland transport still takes place by human porters or carts drawn or pushed by humans.

Pack Animals Horses are used as a draught animal even in the Western countries. Dogs and reindeer are used in North America, North Europe and Siberia to draw sledges over snow-covered ground. Mules are preferred in the mountainous regions; while camels are used for caravan movement in deserts. In India, bullocks are used for pulling carts.

Fig. 8.2: A horse cart in a village Tefki, in Ethiopia

Roads Road transport is the most economical for short distances compared to railways. Freight transport by road is gaining importance because it offers door -to-door service. But unmetalled roads, though simple in construction, are not effective and serviceable for all seasons. During the rainy season these become unmotorable and even the metalled ones are seriously handicapped during heavy rains and floods. In such conditions, the high embankment of rail-tracks and the efficient maintenance of railway transport service, is an effective solution. But the rail kilometrage being small cannot serve the needs of vast and developing countries at a low cost. Roads, therefore, play a vital role in a nation’s trade and commerce and for promoting tourism. The quality of the roads varies greatly between developed and developing countries because road construction and maintenance require heavy expenditure. In developed countries good quality roads are universal and provide long-distance links in the form of motorways, autobahns (Germany), and inter– state highways for speedy movement. Lorries, of increasing size and power to carry heavy loads, are common. But unfortunately, the world’s road system is not well developed. The world’s total motorable road length is only about 15 million km, of which North America accounts for 33 per cent. The highest road density and the highest number of vehicles are registered in this continent compared to Western Europe.

the road network cannot cope with the demands of traffic, congestion occurs. City roads suffer from chronic traffic congestion. Peaks (high points) and troughs (low points) of traffic flow can be seen on roads at particular times of the day, for example, peaks occurring during the rush hour before and after work. Most of the cities in the world have been facing the problem of congestion.

Think on these lines for a better tomorrow . . . URBAN TRANSPORT SOLUTIONS Higher Parking Fee Mass Rapid Transit (MRT) Improved Public Bus Service Expressways

Highways Highways are metalled roads connecting distant places. They are constructed in a manner for unobstructed vehicular movement. As such these are 80 m wide, with separate traffic lanes, bridges, flyovers and dual carriageways to facilitate uninterrupted traffic flow. In developed countries, every city and port town is linked through highways.

Table 8.1: Length of the Roads

Sl. No.

Countries

For every 100 km2 area

1. 2. 3. 4. 5. 6. 7.

India Japan France U.K. U.S.A. Spain Sri Lanka

105 327 164 162 67 68 151

Source : Encyclopedia Britannica – Year Book, 2005.

Traffic Flows: Traffic on roads has increased dramatically in recent years. When

Fig. 8.3 : Dharmavaram Tuni National Highway, India

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In North America, highway density is high, about 0.65 km per sq km. Every place is within 20 km distance from a highway. Cities located on the Pacific coast (west) are well-connected with those of the Atlantic Coast (east). Likewise, the cities of Canada in the north are linked with those of Mexico in the south. The TransCanadian Highway links Vancouver in British Columbia(west coast) to St. John’s City in Newfoundland (east coast) and the Alaskan Highway links Edmonton (Canada) to Anchorage (Alaska). The Pan-American Highway, a large portion of which has been constructed, will connect the countries of South America, Central America and U.S.A.-Canada. The TransContinental Stuart Highway connects Darwin (north coast) and Melbourne via Tennant Creek and Alice Springs in Australia. Europe has a large number of vehicles and a well-developed highway network. But highways face a lot of competition from railways and waterways. In Russia, a dense highway network is developed in the industrialised region west of the Urals with Moscow as the hub. The important Moscow-Vladivostok Highway serves the region to the east. Due to the vast geographical area, highways in Russia are not as important as railways. In China, highways criss-cross the country connecting all major cities such as Tsungtso (near Vietnam boundary), Shanghai (central China), Guangzhou (south) and Beijing (north). A new highway links Chengdu with Lhasa in Tibet. In India, there are many highways linking the major towns and cities. For example, National Highway No. 7 (NH 7), connecting Varanasi with Kanya Kumari, is the longest in the country. The Golden Quadrilateral (GQ) or Super Expressway is underway to connect the four metropolitan cities — New Delhi, Mumbai, Bangalore, Chennai, Kolkata and Hyderabad. In Africa, a highway joins Algiers in the north to Conakry in Guinea. Similarly, Cairo is also connected to Cape Town. 68

Fundamentals of Human Geography

Border Roads Roads laid along international boundaries are called border roads. They play an important role in integrating people in remote areas with major cities and providing defence. Almost all countries have such roads to transport goods to border villages and military camps.

Railways Railways are a mode of land transport for bulky goods and passengers over long distances. The railway gauges vary in different countries and are roughly classified as broad (more than 1.5 m), standard (1.44 m), metre gauge (1 m) and smaller gauges. The standard gauge is used in the U.K. Commuter trains are very popular in U.K., U.S.A, Japan and India. These carry millions of passengers daily to and fro in the city. There are about 13 lakh km of railways open for traffic in the world.

Fig. 8.4: Tube Train in Vienna Table 8.2: Total Length of Railways in Selected Countries (in 100 sq km)

Sl. No.

Countries

1. 2. 3. 4. 5. 6. 7. 8. 9.

U.S.A. Russia India Canada Germany China Australia U.K. France

10.

Brazil

For every 100/km2 area 278.3 160.8 144.7 93.5 90.8 70.1 40.0 37.9 34.5 30.1

Source : Encyclopaedia Britanica – Year Book, 2005.

Europe has one of the most dense rail networks in the world. There are about 4,40,000 km of railways, most of which is double or multiple-tracked. Belgium has the highest density of 1 km of railway for every 6.5 sq kms area. The industrial regions exhibit some of the highest densities in the world. The important rail heads are London, Paris, Brussels, Milan, Berlin and Warsaw. Passenger transport is more important than freight in many of these countries. Underground railways are important in London and Paris. Channel Tunnel, operated by Euro Tunnel Group through England, connects London with Paris. Trans-continental railway lines have now lost their importance to quicker and more flexible transport systems of airways and roadways. In Russia, railways account for about 90 per cent of the country’s total transport with a very dense network west of the Urals. Moscow is the most important rail head with major lines radiating to different parts of the country’s vast geographical area. Underground railways and commuter trains are also important in Moscow. North America has one of the most extensive rail networks accounting for nearly 40 per cent of the world’s total? In contrast to many European countries, the railways are used more for long-distance bulky freight like ores, grains, timber and machinery than for passengers. The most dense rail network is found in the highly industrialised and urbanised region of East Central U.S.A. and adjoining Canada. In Canada, railways are in the public sector and distributed all over the sparsely populated areas. The transcontinental railways carry the bulk of wheat and coal tonnage. Australia has about 40,000 km of railways, of which 25 per cent are found in New South Wales alone. The west-east Australian National Railway line runs across the country from Perth to Sydney. New Zealand’s railways are mainly in the North Island to serve the farming areas. In South America, the rail network is the most dense in two regions, namely, the Pampas of Argentina and the coffee growing region of Brazil which together account for 40 per cent

of South America’s total route length. Only Chile, among the remaining countries has a considerable route length linking coastal centres with the mining sites in the interior. Peru, Bolivia, Ecuador, Colombia and Venezuela have short single-track rail-lines from ports to the interior with no inter-connecting links. There is only one trans-continental rail route linking Buenos Aires (Argentina) with Valparaiso (Chile) across the Andes Mountains through the Uspallatta Pass located at a height of 3,900 m. In Asia, rail network is the most dense in the thickly populated areas of Japan, China and India. Other countries have relatively few rail routes. West Asia is the least developed in rail facilities because of vast deserts and sparsely populated regions.

Africa continent, despite being the second largest, has only 40,000 km of railways with South Africa alone accounting for 18,000 km due to the concentration of gold, diamond and copper mining activities. The important routes of the continent are: (i) the Benguela Railway through Angola to Katanga-Zambia Copper Belt; (ii) the Tanzania Railway from the Zambian Copper Belt to Dar-es-Salaam on the coast; (iii) the Railway through Botswana and Zimbabwe linking the landlocked states to the South African network; and (iv) the Blue Train from Cape Town to Pretoria in the Republic of South Africa. Elsewhere, as in Algeria, Senegal, Nigeria, Kenya and Ethiopia, railway lines connect port cities to interior centres but do not form a good network with other countries.

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Trans–Continental Railways Trans–continental railways run across the continent and link its two ends. They were constructed for economic and political reasons to facilitate long runs in different directions. The following are the most important of these:

Trans–Siberian Railway This is a trans–siberian Railways major rail route of Russia runs from St. Petersburg in the west to Vladivostok on the Pacific Coast in the east passing through Moscow, Ufa, Novosibirsk, Irkutsk, Chita and Khabarovsk. It is the most important route in Asia and the longest (9,332 km) double-tracked and electrified trans– continental railway in the world. It has helped in opening up its Asian region to West European markets. It runs across the Ural Mountains Ob and Yenisei rivers Chita is an important agro-

centre and Irkutsk, a fur centre. There are connecting links to the south, namely, to Odessa (Ukraine), Baku on the Caspian Coast, Tashkent (Uzbekistan), Ulan Bator (Mongolia), and Shenyang (Mukden) and Beijing in China.

Trans–Canadian Railways This 7,050 km long rail-line in Canada runs from Halifax in the east to Vancouver on the Pacific Coast passing through Montreal, Ottawa, Winnipeg and Calgary (Fig. 8.6). It was constructed in 1886, initially as part of an agreement to make British Columbia on the west coast join the Federation of States. Later on, it gained economic significance because it connected the Quebec-Montreal Industrial Region with the wheat belt of the Prairie Region and the Coniferous Forest region in the north. Thus each of these regions became complementary to the other. A loop line from

Fig. 8.5: Trans–Siberian Railway

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Fundamentals of Human Geography

Fig. 8.6: Trans–Canadian Railway

Winnipeg to Thunder Bay (Lake Superior) connects this rail-line with one of the important waterways of the world. This line is the economic artery of Canada. Wheat and meat are the important exports on this route.

The Union and Pacific Railway This rail-line connects New York on the Atlantic Coast to San Francisco on the Pacific Coast passing through Cleveland, Chicago, Omaha, Evans, Ogden and Sacramento. The most valuable exports on this route are ores, grain, paper, chemicals and machinery.

The Australian Trans–Continental Railway This rail-line runs west-east across the southern part of the continent from Perth on the west coast, to Sydney on the east coast. passing through Kalgoorlie, Broken Hill and Port Augusta (Fig. 8.7).

Another major north-south line connects Adelaide and Alice Spring and to be joined further to the Darwin–Birdum line.

The Orient Express This line runs from Paris to Istanbul passing through Strasbourg, Munich, Vienna, Budapest and Belgrade. The journey time from London to Istanbul by this Express is now reduced to 96 hours as against 10 days by the sea-route. The chief exports on this rail-route are cheese, bacon, oats, wine, fruits, and machinery. There is a proposal to build a Trans–Asiatic Railway linking Istanbul with Bangkok via Iran, Pakistan, India, Bangladesh and Myanmar.

WA TER TRANSPOR T WATER TRANSPORT One of the great advantages of water transportation is that it does not require route construction. The oceans are linked with each Transport and Communication

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Fig. 8.7: Australian Trans–Continental Railway

other and are negotiable with ships of various sizes. All that is needed is to provide port facilities at the two ends. It is much cheaper because the friction of water is far less than that of land. The energy cost of water transportation is lower. Water transport is divided into ocean routes and inland waterways.

Ocean Routes The oceans offer a smooth highway traversable in all directions with no maintenance costs. Its transformation into a routeway by sea-going vessels is an important development in human adaptation to the physical environment. Compared to land and air, ocean transport is a cheaper means of haulage (carrying of load) of bulky material over long distances from one continent to another. Modern passenger liners (ships) and cargo ships are equipped with radar, wireless and other navigation aids. The development of refrigerated chambers for perishable goods, tankers and specialised ships has also improved cargo transport. The use of containers has made cargo handling at the world’s major ports easier.

Important Ocean Routes Fig. 8.8: The view of Seine River from the Eiffel Tower (One can see how the river has become an important Inland waterway)

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Fundamentals of Human Geography

Major ocean trade routes are shown in the Fig. 8.9. Some important ocean routes have been discussed in the following pages.

Fig. 8.9: Major Ocean Trade Routes and Sea Ports

The Northern Atlantic Sea Route

The Mediterranean–Indian Ocean Route

This links North-eastern U.S.A. and Northwestern Europe, the two industrially developed regions of the world. The foreign trade over this route is greater than that of the rest of the world combined. One fourth of the world’s foreign trade moves on this route. It is, therefore, the busiest in the world and otherwise, called the Big Trunk Route. Both the coasts have highly advanced ports and harbour facilities.

The trade route connects the highly industrialised Western European region with West Africa, South Africa, South-east Asia and the commercial agriculture and livestock economies of Australia and New Zealand. Before the construction of the Suez Canal this was the route connecting Liverpool and Colombo which was 6,400 km longer than the Suez Canal route. The volume of trade and traffic between both East and West Africa is on the increase due to the development of the rich natural resources such as gold, diamond, copper, tin, groundnut, oil palm, coffee and fruits.

Find out some of the important ports on the coast of U.S.A. and Western Europe in your atlas.

This sea route passes through the heart of the Old World and serves more countries and people than any other route. Port Said, Aden, Mumbai, Colombo and Singapore are some of the important ports on this route. The construction of Suez canal has greatly reduced the distance and time as compared to the earlier route through the Cape of Good Hope.

The Cape of Good Hope Sea Route This sea route is another important one across the Atlantic Ocean which connects West European and West African countries with Brazil, Argentina and Uruguay in South America. The traffic is far less on this route compared to that of the North Atlantic Route Transport and Communication

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because of the limited development and population in South America and Africa. Only southeastern Brazil and Plata estuary and parts of South Africa have large-scale industries. There is also little traffic on the route between Rio de Janeiro and Cape Town because both South America and Africa have similar products and resources. Trade across the vast North Pacific Ocean moves by several routes which converge at Honolulu. The direct route on the Great Circle links Vancouver and Yokohama and reduces the travelling distance (2,480 km) by half. The North Atlantic Sea Route This sea route links the ports on the west-coast of North America with those of Asia. These are Vancouver, Seattle, Portland, San Francisco and Los Angeles on the American side and Yokohama, Kobe, Shanghai, Hong Kong, Manila and Singapore on the Asian side.

The Suez Canal This canal had been constructed in 1869 in Egypt between Port Said in the north and Port Suez in the south linking the Mediterranean Sea and the Red Sea. It gives Europe a new gateway to the Indian Ocean and reduces direct sea-route distance between Liverpool and Colombo compared to the Cape of Good Hope route. It is a sea-level canal without locks which is about 160 km and 11 to 15 m deep. About 100 ships travel daily and each ship takes 10-12 hours to cross this canal. The tolls are so heavy that some find it cheaper to go by the longer Cape Route whenever the consequent delay is not important. A railway follows the canal to Suez, and from Ismailia there is a branch line to Cairo. A navigable fresh-water canal from the Nile also joins the Suez Canal in Ismailia to supply fresh-water to Port Said and Suez.

The South Pacific Sea Route This sea route connects Western Europe and North America with Australia, New Zealand and the scattered Pacific islands via the Panama Canal. This route is also used for reaching Hong Kong, Philippines and Indonesia. The distance covered between Panama and Sydney is 12,000 km. Honolulu is an important port on this route. Coastal Shipping It is obvious that water transport is a cheaper mode. While oceanic routes connect different countries, coastal shipping is a convenient mode of transportation with long coastlines, e.g. U.S.A, China and India. Shenzhen States in Europe are most suitably placed for coastal shipping connecting one member’s coast with the other. If properly developed, coastal shipping can reduce the congestion on the land routes. Shipping Canals The Suez and the Panama Canals are two vital man-made navigation canals or waterways which serve as gateways of commerce for both the eastern and western worlds. 74

Fundamentals of Human Geography

Fig. 8.10 : Suez Canal

The Panama Canal This canal connects the Atlantic Ocean in the east to the Pacific Ocean in the west. It has been

constructed across the Panama Isthmus between Panama City and Colon by the U.S. government which purchased 8 km of area on either side and named it the Canal Zone. The Canal is about 72 km. long and involves a very deep cutting for a length of 12 km. It has a sixlock system and ships cross the different levels (26 m up and down) through these locks before entering the Gulf of Panama. It shortens the distance between New York and San Francisco by 13,000 km by sea. Likewise the distance between Western Europe and the West-coast of U.S.A.; and North-eastern and Central U.S.A. and East and South-east Asia is shortened. The economic significance of this Canal is relatively less than that of the Suez. However, it is vital to the economies of Latin America.

Inland Waterways

Fig. 8.11 : The Panama Canal

Can you think of the impact on traffic in Panama canal after the Nicaraguan canal opens up?

Rivers, canals, lakes and coastal areas have been important waterways since time immemorial. Boats and steamers are used as means of transport for cargo and passengers. The development of inland waterways is dependent on the navigability width and depth of the channel, continuity in the water flow, and transport technology in use. Rivers are the only means of transport in dense forests. Very heavy cargo like coal, cement, timber and metallic ores can be transported through inland waterways. In ancient times, riverways were the main highways of transportation as in the case of India. But they lost importance because of competition from railways, lack of water due to diversion for irrigation, and their poor maintenance.

Fig. 8.12: Inland waterways are a major source of transport wherever the river is wide, deep and free of silt

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The significance of rivers as inland waterways for domestic and international transport and trade has been recognised throughout the developed world. Despite inherent limitations, many rivers have been modified to enhance their navigability by dredging, stabilising river banks, and building dams and barrages for regulating the flow of water. The following river waterways are some of the world’s important highways of commerce.

The Rhine Waterways The Rhine flows through Germany and the Netherlands. It is navigable for 700 km from Rotterdam, at its mouth in the Netherlands to Basel in Switzerland. Ocean-going vessels can reach up to Cologne. The Ruhr river joins the Rhine from the east. It flows through a rich coalfield and the whole basin has become a prosperous manufacturing area. Dusseldorf is the Rhine port for this region. Huge tonnage moves along the stretch south of the Ruhr. This waterway is the world’s most heavily used. Each year more than 20,000 ocean-going ships and 2,00,000 inland vessels exchange their cargoes. It connects the industrial areas of Switzerland, Germany, France, Belgium and the Netherlands with the North Atlantic Sea Route.

Fig. 8.14 : Rhine Waterway

The Volga Waterway Russia has a large number of developed waterways, of which the Volga is one of the most important. It provides a navigable waterway of 11,200 km and drains into the Caspian Sea. The Volga-Moscow Canal connects it with the Moscow region and the Volga-Don Canal with the Black Sea. The Great Lakes – St. Lawrence Seaway

Fig. 8.13: The Rhine Watereay

The Danube Waterway This important inland waterway serves Eastern Europe. The Danube river rises in the Black Forest and flows eastwards through many countries. It is navigable up to Taurna Severin. The chief export items are wheat, maize, timber, and machinery. 76

Fundamentals of Human Geography

The Great Lakes of North America Superior, Huron Erie and Ontario are connected by Soo Canal and Welland Canal to form an inland waterway. The estuary of St. Lawrence River, along with the Great Lakes, forms a unique commercial waterway in the northern part of North America. The ports on this route like Duluth and Buffalo are equipped with all facilities of ocean ports. As such large oceangoing vessels are able to navigate up the river deep inside the continent to Montreal. But here goods have to be trans-shipped to smaller vessels due to the presence of rapids. Canals have been constructed up to 3.5 m deep to avoid these.

The Mississippi Waterways The Mississippi-Ohio waterway connects the interior part of U.S.A. with the Gulf of Mexico in the south. Large steamers can go through this route up to Minneapolis.

AIR TRANSPOR T TRANSPORT Air transport is the fastest means of transportation, but it is very costly. Being fast, it is preferred by passengers for long-distance travel. Valuable cargo can be moved rapidly on a world-wide scale. It is often the only means to reach inaccessible areas. Air transport has brought about a connectivity revolution in the world. The frictions created by mountainous snow fields or inhospitable desert terrains have been overcome. The accessibility has increased. The airplane brings varied articles to the Eskimos in Northern Canada unhindered by the frozen ground. In the Himalayan region, the routes are often obstructed due to landslides, avalanches or heavy snow fall. At such times, air travel is the only alternative to reach a place. Airways also have great strategic importance. The air strikes by U.S. and British forces in Iraq bears testimony to this fact. The airways network is expanding very fast.

At present no place in the world is more than 35 hours away. This startling fact has been made possible due to people who build and fly airplanes. Travel by air can now be measured by hours and minutes instead of years and months. Frequent air services are available to many parts of the world. Although, U.K. pioneered the use of commercial jet transport, U.S.A. developed largely post-War international civil aviation. Today, more than 250 commercial airlines offer regular services to different parts of the world. Recent developments can change the future course of air transport. Supersonic aircraft, cover the distance between London and New York within three and a half hours.

Inter-Continental Air Routes In the Northern Hemisphere, there is a distinct east-west belt of inter-continental air routes. Dense network exists in Eastern U.S.A., Western Europe and Southeast Asia. U.S.A. alone accounts for 60 per cent of the airways of the world. New York, London, Paris, Amsterdam, Frankfurt Rome, Moscow, Karachi, New Delhi, Mumbai, Bangkok, Singapore, Tokyo, San Francisco, Los Angeles and Chicago are the nodal points where air routes converge or radiate to all continents. Africa, Asiatic part of Russia and South America lack air services. There are limited air services between 10-35 latitudes in the Southern hemisphere due to sparser population, limited landmass and economic development.

PIPELINES

Fig. 8.15: An Aeroplane at Salsburg Airport

The manufacturing of aircrafts and their operations require elaborate infrastructure like hangars, landing, fuelling, and maintenance facilities for the aircrafts. The construction of airports is also very expensive and has developed more in highly industrialised countries where there is a large volume of traffic.

Pipelines are used extensively to transport liquids and gases such as water, petroleum and natural gas for an uninterrupted flow. Water supplied through pipelines is familiar to all. Cooking gas or LPG is supplied through pipelines in many parts of the world. Pipelines can also be used to transport liquidified coal. In New Zealand, milk is being supplied through pipelines from farms to factories. In U.S.A. there is a dense network of oil pipelines from the producing areas to the Transport and Communication

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Fig. 8.16: Major Airports

consuming areas. Big Inch is one such famous pipeline, which carries petroleum from the oil wells of the Gulf of Mexico to the North-eastern States. About 17 per cent of all freight per tonne-km. is carried through pipelines in U.S.A.

Fig. 8.17: Pipelines transporting natural gas in Ukraine

In Europe, Russia, West Asia and India pipelines are used to connect oil wells to refineries, and to ports or domestic markets. Turkmenistan is central Asia has extended pipelines to Iran and also to parts of China. 78

Fundamentals of Human Geography

The proposed Iran-India via Pakistan international oil and natural gas pipeline will be the longest in the world.

COMMUNICA TIONS COMMUNICATIONS Human beings have used different methods long-distance communications of which the telegraph and the telephone were important. The telegraph was instrumental in the colonisation of the American West. During the early and mid-twentieth century, the American Telegraph and Telephone Company (AT&T) enjoyed a monopoly over U.S.A.’s telephone industry. In fact, the telephone became a critical factor in the urbanisation of America. Firms centralised their functioning at cityheadquarters and located their branch offices in smaller towns. Even today, the telephone is the most commonly used mode. In developing countries, the use of cell phones, made possible by satellites, is important for rural connectivity. Today there is a phenomenal pace of development. The first major breakthrough is the use of optic fiber cables (OFC). Faced with mounting competition, telephone companies all

over the world soon upgraded their copper cable systems to include optic fiber cables. These allow large quantities of data to be transmitted rapidly, securely, and are virtually error-free. With the digitisation of information in the 1990s, telecommunication slowly merged with computers to form integrated networks termed as Internet.

Satellite Communication Today Internet is the largest electronic network on the planet connecting about 1,000 million people in more than 100 countries. Satellites touch human lives in many ways. Every time you use a cell phone to call a friend, send an SMS or watch a popular programme on cable television. You are using satellite communication.

Communication through satellites emerged as a new area in communication technology since the 1970s after U.S.A. and former U.S.S.R. pioneered space research. Artificial satellites, now, are successfully deployed in the earth’s orbit to connect even the remote corners of the globe with limited onsite verification. These have rendered the unit cost and time of communication invariant in terms of distance. This means it costs the same to communicate over 500 km as it does over 5,000 km via satellite India has also made great strides in satellite development. Aryabhatt was launched on 19 April 1979, Bhaskar-I in 1979 and Rohini in 1980. On 18 June 1981, APPLE (Arian Passenger Payload Experiment) was launched through Arian rocket. Bhaskar,

Challenger and INSAT I-B have made longdistance communication, television and radio very effective. Today weather forecasting through television is a boon.

Cyber Space – Internet Cyberspace is the world of electronic computerised space. It is encompassed by the Internet such as the World Wide Web (www). In simple words, it is the electronic digital world for communicating or accessing information over computer networks without physical movement of the sender and the receiver... It is also referred to as the Internet. Cyberspace exists everywhere. It may be in an office, sailing boat, flying plane and virtually anywhere. The speed at which this electronic network has spread is unprecedented in human history. There were less than 50 million Internet users in 1995, about 400 million in 2000 A.D. and over one billion in 2005. The next billion users are to be added by 2010. In the last five years there has been a shift among global users from U.S.A. to the developing countries. The percentage share of U.S.A. has dropped from 66 in 1995 to only 25 in 2005. Now the majority of the world’s users are in U.S.A., U.K., Germany, Japan, China and India. As billions use the Internet each year, cyberspace will expand the contemporary economic and social space of humans through e-mail, e-commerce, e-learning and e-governance. Internet together with fax, television and radio will be accessible to more and more people cutting across place and time. It is these modern communication systems, more than transportation, that has made the concept of global village a reality.

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EXERCISES 1.

Choose the right answer from the four alternatives given below. (i)

The Trans–Continental Stuart Highway runs between (a)

(ii)

(iii)

(iv)

(v)

2.

(ii) (iii)

80

(b)

Edmonton and Anchorage

(c)

Vancouver and St. John’s City

(d)

Chengdu and Lhasa

Which country has the highest density of railway network? (a)

Brazil

(c)

Canada

(b)

U.S.A

(d)

Russia

The Big Trunk Route runs through (a)

The Mediterranean – Indian ocean

(b)

The North Atlantic Ocean

(c)

The South Atlantic Ocean

(d)

The North Pacific Ocean

The Big Inch pipeline transports (a)

Milk

(c)

Water

(b)

Liquid petroleum gas (LGP)

(d)

Petroleum

Which one pair of the following places is linked by Channel Tunnel? (a)

London – Berlin

(c)

Berlin – Paris

(b)

Paris – London

(d)

Barcelona – Berlin

Answer the following questions in about 30 words. (i)

3.

Darwin and Melbourne

What are the problems of road transport in mountainous, desert and flood prone regions? What is a trans–continental railway? What are the advantages of water transport?

Answer the following questions in not more than 150 words. (i)

Elucidate the statement– “In a well managed transport system, various modes complement each other”.

(ii)

Which are the major regions of the world having a dense network of airways.

(iii)

What are the modes by which cyber space will expand the contemporary economic and social space of humans.

Fundamentals of Human Geography

Unit-III Chapter-9

International Trade

You are already familiar with the term “trade” as a tertiary activity which you have studied in Chapter 7 of this book. You know that trade means the voluntary exchange of goods and services. Two parties are required to trade. One person sells and the other purchases. In certain places, people barter their goods. For both the parties trade is mutually beneficial. Trade may be conducted at two levels: international and national. International trade is the exchange of goods and services among countries across national boundaries. Countries need to trade to obtain commodities, they cannot produce themselves or they can purchase elsewhere at a lower price. The initial form of trade in primitive societies was the barter system, where direct exchange of goods took place. In this system if you were a potter and were in need of a plumber, you would have to look for a plumber who would be in need of pots and you could exchange your pots for his plumbing service.

Fig. 9.1: Two women practising barter system in Jon Beel Mela

Every January after the harvest season Jon Beel Mela takes place in Jagirod, 35 km away from Guwahati and it is possibly the only fair In India, where barter system is still alive. A big market is organised during this fair and people from various tribes and communities exchange their products.

The difficulties of barter system were overcome by the introduction of money. In the olden times, before paper and coin currency

came into being, rare objects with very high intrinsic value served as money, like, flintstones, obsidian, cowrie shells, tiger’s paws, whale’s teeth, dogs teeth, skins, furs, cattle, rice, peppercorns, salt, small tools, copper, silver and gold.

The word salary comes from the Latin word Salarium which means payment by salt. As in those times producing salt from sea water was unknown and could only be made from rock salt which was rare and expensive. That is why it became a mode of payment.

HISTORY OF INTERNATIONAL TRADE In ancient times, transporting goods over long distances was risky, hence trade was restricted to local markets. People then spent most of their resources on basic necessities – food and clothes. Only the rich people bought jewellery, costly dresses and this resulted in trade of luxury items. The Silk Route is an early example of long distance trade connecting Rome to China – along the 6,000 km route. The traders transported Chinese silk, Roman wool and precious metals and many other high value commodities from intermediate points in India, Persia and Central Asia. After the disintegration of the Roman Empire, European commerce grew during twelfth and thirteenth century with the development of ocean going warships trade between Europe and Asia grew and the Americas were discovered. Fifteenth century onwards, the European colonialism began and along with trade of exotic commodities, a new form of trade emerged which was called slave trade. The Portuguese, Dutch, Spaniards, and British captured African natives and forcefully transported them to the newly discovered Americas for their labour in the plantations. Slave trade was a lucrative business for more than two hundred years till it was abolished in Denmark in 1792, Great Britain in 1807 and United States in 1808.

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Figure 9.2 : Advertisement for Slave Auction, 1829

This American slave auction advertised slaves for sale or temporary hire by their owners. Buyers often paid as much as $2,000 for a skilled, healthy slave. Such auctions often separated family members from one another, many of whom never saw their loved ones again.

After the Industrial Revolution the demand for raw materials like grains, meat, wool also expanded, but their monetary value declined in relation to the manufactured goods. The industrialised nations imported primary products as raw materials and exported the value added finished products back to the non-industrialised nations. In the later half of the nineteenth century, regions producing primary goods were no more important, and industrial nations became each other’s principle customers. During the World Wars I and II, countries imposed trade taxes and quantitative restrictions for the first time. During the postwar period, organisations like General Agreement for Tariffs and Trade (which later became the World Trade Organisation), helped in reducing tariff.

Why Does International Trade Exist? International trade is the result of specialisation in production. It benefits the world economy if

different countries practise specialisation and division of labour in the production of commodities or provision of services. Each kind of specialisation can give rise to trade. Thus, international trade is based on the principle of comparative advantage, complimentarity and transferability of goods and services and in principle, should be mutually beneficial to the trading partners. In modern times, trade is the basis of the world’s economic organisation and is related to the foreign policy of nations. With welldeveloped transportation and communication systems, no country is willing to forego the benefits derived from participation in international trade.

Basis of International Trade (i) Difference in national resources: The world’s national resources are unevenly distributed because of differences in their physical make up i.e. geology, relief soil and climate. (a) Geological structure: It determines the mineral resource base and topographical differences ensure diversity of crops and animals raised. Lowlands have greater agricultural potential. Mountains attract tourists and promote tourism. (b) Mineral resources: They are unevenly distributed the world over. The availability of mineral resources provides the basis for industrial development. (c) Climate: It influences the type of flora and fauna that can survive in a given region. It also ensures diversity in the range of various products, e.g. wool production can take place in cold regions, bananas, rubber and cocoa can grow in tropical regions. (ii) Population factors: The size, distribution and diversity of people between countries affect the type and volume of goods traded. (a) Cultural factors: Distinctive forms of art and craft develop in certain

cultures which are valued the world over, e.g. China produces the finest porcelains and brocades. Carpets of Iran are famous while North African leather work and Indonesian batik cloth are prized handicrafts. (b) Size of population: Densely populated countries have large volume of internal trade but little external trade because most of the agricultural and industrial production is consumed in the local markets. Standard of living of the population determines the demand for better quality imported products because with low standard of living only a few people can afford to buy costly imported goods. (iii) Stage of economic development: At different stages of economic development of countries, the nature of items traded undergo changes. In agriculturally important countries, agro products are exchanged for manufactured goods whereas industrialised nations export machinery and finished products and import food grains and other raw materials. (iv) Extent of foreign investment: Foreign investment can boost trade in developing countries which lack in capital required for the development of mining, oil drilling, heavy engineering, lumbering and plantation agriculture. By developing such capital intensive industries in developing countries, the industrial nations ensure import of food stuffs, minerals and create markets for their finished products. This entire cycle steps up the volume of trade between nations. (v) T ransport: In olden times, lack of adequate and efficient means of transport restricted trade to local areas. Only high value items, e.g. gems, silk and spices were traded over long distances. With expansions of rail, ocean and air transport, better means of refrigeration and preservation, trade has experienced spatial expansion. International Trade

83

Important Aspects of International Trade International trade has three very important aspects. These are volume, sectoral composition and direction of trade.

Billion $

Goods

12000

Billion $

Services

10500

12000 10500

9000

9000

7500

7500

6000

6000

4500

4500

Volume of Trade

3000

3000

The actual tonnage of goods traded makes up the volume. However, services traded cannot be measured in tonnage. Therefore, the total value of goods and services traded is considered to be the volume of trade. Table 9.1 shows that the total volume of world trade has been steadily rising over the past decades.

1500

1500

Why do you think that the volume of trade has increased over the decades? Can these figures be compared? What has been the growth in the year 2005 over the year 1955?

Composition of Trade The nature of goods and services imported and exported by countries have undergone changes during the last century. Trade of primary products was dominant in the beginning of the last century. Later manufactured goods gained prominence and currently, though the manufacturing sector commands the bulk of the global trade, service sector which includes travel, transportation and other commercial services have been showing an upward trend.

00

98

20

96

94

92

90

88

86

84

19

82

0

80

0

Source: WTO, Trade Statistics, 2002.

Fig. 9.3: Exports of Goods and Services, 1980-2000

The share of different commodities in total global trade can be seen in the graph below. Machinery and Transport Equipment Fuels & Mining Road Office/Telecome Equipment Chemicals Automotive Products Agriculture Products Other Manufactures Other Semi–manufactures Iron & Steel Clothing Textiles 0

5 10 15 Percentage to total value

20

Source: WTO, Trade Statistics, 2005

Fig. 9.4: World Merchandise Exports By Products, 2004

Looking at the graph above, we find that machinery and transport equipment, fuel and mining products, office and telecom equipment, chemicals, automobile parts, agricultural

Table 9.1: World Imports and Exports (in millions of U.S. $)

Exports

1955

1965

1975

1985

1995

2005

95000

190000

877000

1954000

5162000

10393000

99000

199000

912000

2015000

5292000

10753000

Total Merchandise Imports Total Merchandise

Source: WTO, International Trade Statistics, 2005

84

Fundamentals of Human Geography

products, iron and steel, clothing and textiles make up the major items of merchandise which are traded over the world. Trade in the service sector is quite different from trade in the products of primary and manufacturing sectors as the services can be expanded infinitely, consumed by many, are weightless and once produced, can be easily replicated and thus, are capable of generating more profit than producing goods. There are four different ways through which services can be supplied. Table 9.2 shows different types of services and the share of those services supplied to the international market. Table 9.2 : Services and their Share to the International Market

Relevant Services Commercial services excluding travel and construction services. Travel Construction services Labour flow

Share in % 35 10 to 15 50 1 to 2

Direction of Trade Historically, the developing countries of the present used to export valuable goods and artefacts, etc. which were exported to European countries. During the nineteenth century there was a reversal in the direction of trade. European countries started exporting manufactured goods for exchange of foodstuffs and raw materials from their colonies. Europe and U.S.A. emerged as major trade partners in the world and were leaders in the trade of manufactured goods. Japan at that time was also the third important trading country. The world trade pattern underwent a drastic change during the second half of the twentieth century. Europe lost its colonies while India, China and other developing countries started competing with developed countries. The nature of the goods traded has also changed.

Balance of Trade Balance of trade records the volume of goods and services imported as well as exported by a country to other countries. If the value of imports is more than the value of a country’s

exports, the country has negative or unfavourable balance of trade. If the value of exports is more than the value of imports, then the country has a positive or favourable balance of trade. Balance of trade and balance of payments have serious implications for a country’s economy. A negative balance would mean that the country spends more on buying goods than it can earn by selling its goods. This would ultimately lead to exhaustion of its financial reserves.

Types of International Trade International trade may be categorised into two types: (a) Bilateral trade: Bilateral trade is done by two countries with each other. They enter into agreement to trade specified commodities amongst them. For example, country A may agree to trade some raw material with agreement to purchase some other specified item to country B or vice versa. (b) Multi-lateral trade: As the term suggests multi-lateral trade is conducted with many trading countries. The same country can trade with a number of other countries. The country may also grant the status of the “Most Favoured Nation” (MFN) on some of the trading partners.

Case for Free Trade The act of opening up economies for trading is known as free trade or trade liberalisation. This is done by bringing down trade barriers like tariffs. Trade liberalisation allows goods and services from everywhere to compete with domestic products and services. Globalisation along with free trade can adversely affect the economies of developing countries by not giving equal playing field by imposing conditions which are unfavourable. With the development of transport and communication systems goods and services can travel faster and farther than ever before. But free trade should not only let rich countries enter the markets, but allow the developed International Trade

85

countries to keep their own markets protected from foreign products. Countries also need to be cautious about dumped goods; as along with free trade dumped goods of cheaper prices can harm the domestic producers.

Dumping The practice of selling a commodity in two countries at a price that differs for reasons not related to costs is called dumping.

countries to set up a permanent institution for looking after the promotion of free and fair trade amongst nation and the GATT was transformed into the World Trade Organisation from 1st January 1995. WTO is the only international organisation dealing with the global rules of trade between nations. It sets the rules for the global trading system and resolves disputes between its member nations. WTO also covers trade in services, such as telecommunication and banking, and others issues such as intellectual rights. The WTO has however been criticised and opposed by those who are worried about the effects of free trade and economic globalisation. It is argued that free trade does not make ordinary people’s lives more prosperous. It is actually widening the gulf between rich and poor by making rich countries more rich. This is because the influential nations in the WTO focus on their own commercial interests. Moreover, many developed countries have not fully opened their markets to products from developing countries. It is also argued that issues of health, worker’s rights, child labour and environment are ignored.

WTO Headquarters are located in Geneva, Switzerland. 149 countries were members of WTO as on December 2005. India has been one of the founder member of WTO.

Regional Trade Blocs Think of some reasons why dumping is becoming a serious concern among trading nations?

World Trade Organisation In1948, to liberalise the world from high customs tariffs and various other types of restrictions, General Agreement for Tariffs and Trade (GATT) was formed by some countries. In 1994, it was decided by the member 86

Fundamentals of Human Geography

Regional Trade Blocs have come up in order to encourage trade between countries with geographical proximity, similarity and complementarities in trading items and to curb restrictions on trade of the developing world. Today, 120 regional trade blocs generate 52 per cent of the world trade. These trading blocs developed as a response to the failure of the global organisations to speed up intra-regional trade. Though, these regional blocs remove trade tariffs within the member nations and

encourage free trade, in the future it could get increasingly difficult for free trade to take place

between different trading blocs. Some major regional trade blocs have been listed in Table 9.3.

Table 9.3: Major Regional Trade Regional Blocs

Head Quarter

Member nations

ASEAN Jakarta, (Association of Indonesia South East Asian Nations)

Brunei, Indonesia, Malaysia, Singapore, Thailand, Vietnam

CIS (Commonwealth of Independent States)

Armenia, Azerbaijan, Belarus, Georgia, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan, Turkmenistan, Ukraine and Uzbekistan.

Minsk, Belarus

Origin

Aug, 1967

—

EU Brussels, (European Union) Belgium

Austria, Belgium, EECDenmark, March 1957 France, Finland, EU - Feb. 1992 Ireland, Italy, the Netherlands, Luxemburg, Portugal, Spain, Sweden and U.K.

LAIA (Latin American Integration Association)

Argentina, Bolivia, 1960 Brazil, Columbia, Ecuador, Mexico, Paraguay, Peru, Uruguay and Venezuela

Montevideo, Uruguay

NAFTA (North American Free Trade Association) OPEC (Organisation of Petroleum Exporting Countries)

SAFTA (South Asian Free Trade Agreement)

Vienna, Austria

Commodities

Agro products, rubber, palm oil, rice, copra, coffee, minerals – copper, coal, nickel and tungsten. Energy – petroleum and natural gas and Software products

Accelerate economic growth, cultural development, peace and regional stability

Crude oil, natural Integration gas, gold, cotton, and fibre, aluminium cooperation on matters of economics, defence and foreign policy

Agro products, minerals, chemicals, wood, paper, transport vehicles, optical instruments, clocks - works of art, antiques

Single market with single currency

—

—

—

U.S.A., Canada and Mexico

1994

Agro products, motor vehicles, automotive parts, computers, textiles

Algeria, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, U.A.E. and Venezuela

1949

Crude petroleum

Bangladesh, Jan-2006 Maldives, Bhutan, Nepal, India, Pakistan and Sri Lanka

Other Areas of Cooperation

—

Coordinate and unify petroleum policies.

Reduce tariffs on interregional trade

International Trade

87

Concerns Related to International Trade Undertaking international trade is mutually beneficial to nations if it leads to regional specialisation, higher level of production, better standard of living, worldwide availability of goods and services, equalisation of prices and wages and diffusion of knowledge and culture. International trade can prove to be detrimental to nations of it leads to dependence on other countries, uneven levels of development, exploitation, and commercial rivalry leading to wars. Global trade affects many aspects of life; it can impact everything from the environment to health and well-being of the people around the world. As countries compete to trade more, production and the use of natural resources spiral up, resources get used up faster than they can be replenished. As a result, marine life is also depleting fast, forests are being cut down and river basins sold off to private drinking water companies. Multinational corporations trading in oil, gas mining, pharmaceuticals and agri-business keep expanding their operations at all costs creating more pollution – their mode of work does not follow the norms of sustainable development. If organisations are geared only towards profit making, and environmental and health concerns are not addressed, then it could lead to serious implications in the future.

Fig. 9.5: San Francisco, the largest land-locked harbour in the world

Types of Port Generally, ports are classified according to the types of traffic which they handle. Types of port according to cargo handled: (i) Industrial Ports: These ports specialise in bulk cargo-like grain, sugar, ore, oil, chemicals and similar materials. (ii) Commercial Ports: These ports handle general cargo-packaged products and manufactured good. These ports also handle passenger traffic.

GATEWAYS OF INTERNATIONAL TRADE Ports The chief gateways of the world of international trade are the harbours and ports. Cargoes and travellers pass from one part of the world to another through these ports. The ports provide facilities of docking, loading, unloading and the storage facilities for cargo. In order to provide these facilities, the port authorities make arrangements for maintaining navigable channels, arranging tugs and barges, and providing labour and managerial services. The importance of a port is judged by the size of cargo and the number of ships handled. The quantity of cargo handled by a port is an indicator of the level of development of its hinterland. 88

Fundamentals of Human Geography

Fig. 9.6: Leningrad Commercial Port

(iii) Comprehensive Ports: Such ports handle bulk and general cargo in large volumes.

Most of the world’s great ports are classified as comprehensive ports. Types of port on the basis of location: (i)

(ii)

Inland Ports: These ports are located away from the sea coast. They are linked to the sea through a river or a canal. Such ports are accessible to flat bottom ships or barges. For example, Manchester is linked with a canal; Memphis is located on the river Mississippi; Rhine has several ports like Mannheim and Duisburg; and Kolkata is located on the river Hoogli, a branch of the river Ganga. Out Ports: These are deep water ports built away from the actual ports. These serve the parent ports by receiving those ships which are unable to approach them due to their large size. Classic combination, for example, is Athens and its out port Piraeus in Greece.

Types of port on the basis of specialised functions: (i)

Oil Ports: These ports deal in the processing and shipping of oil. Some of these are tanker ports and some are refinery ports. Maracaibo in Venezuela, Esskhira in Tunisia, Tripoli in Lebanon are

tanker ports. Abadan on the Gulf of Persia is a refinery port. (ii) Ports of Call: These are the ports which originally developed as calling points on main sea routes where ships used to anchor for refuelling, watering and taking food items. Later on, they developed into commercial ports. Aden, Honolulu and Singapore are good examples. (iii) Packet Station: These are also known as ferry ports. These packet stations are exclusively concerned with the transportation of passengers and mail across water bodies covering short distances. These stations occur in pairs located in such a way that they face each other across the water body, e.g. Dover in England and Calais in France across the English Channel. (iv) Entrepot Ports: These are collection centres where the goods are brought from different countries for export. Singapore is an entrepot for Asia. Rotterdam for Europe, and Copenhagen for the Baltic region. (v) Naval Ports: These are ports which have only strategic importance. These ports serve warships and have repair workshops for them. Kochi and Karwar are examples of such ports in India.

EXERCISES 1.

Choose the right answer from the four alternatives given below. (i) Most of the world’s great ports are classified as: (a) Naval Ports (c) Comprehensive Ports (b) (ii)

Oil Ports

(d)

Industrial Ports

Which one of the following continents has the maximum flow of global trade? (a)

Asia

(c)

Europe

(b)

North America

(d)

Africa

International Trade

89

(iii)

(iv)

Which one of the following South American nation, is a part of OPEC? (a)

Brazil

(c)

Venezuela

(b)

Chile

(d)

Peru

In which of the following trade blocs, is India an associate member? (a)

2.

(ii) 3.

(c)

ASEAN

Why is it detrimental for a nation to have negative balance of payments?

(iii) What benefits do nations get by forming trading blocs? Answer the following questions in not more than 150 words: (i) How are ports helpful for trade? Give a classification of ports on the basis of their location. (ii)

90

SAFTA

(b) OECD (d) OPEC Answer the following questions in about 30 words: (i) What is the basic function of the World Trade Organisation?

How do nations gain from International Trade?

Fundamentals of Human Geography

Appendix I World Population : Selected Data, 2000 Region/Country

Surface Area Population by (thousand the year 2000 sq km) (million)

Density of Population (per sq km)

Growth 1990–95

Rate 1995–2000

World

–

6,005

–

1.7

1.3

Africa

–

784.4

–

2.9

2.4

Algeria

2,382

31.5

13

2.7

2.3

Angola

1,247

12.9

11

3.7

3.2

Benin

113

6.1

57

3.1

2.7

Botswana

582

1.6

3

2.9

1.9

Burkina Faso

274

11.9

41

2.8

2.7

28

6.7

265

2.9

1.7

Cameroon

475

15.1

32

2.8

2.7

Central African Republic

623

3.6

6

2.6

1.9

Chad

1,284

7.7

6

2.7

2.6

Democratic Republic of Congo

2,345

51.7

22

3

2.6

Burundi

Republic of Congo

342

2.9

9

–

2.8

Cote d’Ivoire

322

14.8

50

3.7

1.8

1,001

68.5

64

2.2

1.9

118

3.9

41

–

3.8

1,104

62.6

64

3.1

2.5

Gabon

268

1.2

5

3.3

2.6

Chana

239

20.2

85

3

2.7

Guinea

246

7.4

30

3

0.8

36

1.2

43

2.1

2.2

580

30.1

53

3.4

2

Egypt Eritrea Ethiopia

Guinea-Bissau Kenya Lesotho

30

2.2

67

2.5

2.2

Liberia

111

3.2

32

3.3

8.2

–

5.6

–

3.5

2.4

Madagascar

587

15.9

27

3.3

3

Malawi

118

10.9

110

3.3

2.4

Mali

1,240

11.2

9

3.2

2.4

Mauritania

1,026

2.7

3

2.9

2.7

2

1.2

584

1

0.8

Morocco

447

28.4

64

2.4

1.8

Mozambique

802

19.7

23

2.8

2.5

Libyan Arab Jamahiriya

Mauritius

Namibia Niger Nigeria

824

1.7

2

3.2

2.2

1,267

10.7

9

3.3

3.2

924

111.5

32.7

3.1

2.4

Region/Country

Surface Area Population by (thousand the year 2000 sq km) (million)

Density of Population (per sq km)

Growth 1990–95

Rate 1995–2000

Rwanda

26

7.7

345

3.4

7.7

Senegal

197

9.5

49

2.7

2.6

72

4.9

70

2.7

3

638

10.1

14

3.2

4.2

South Africa

1,221

40.4

35

2.4

1.5

Sudan

2,506

29.5

13

2.8

2.1

57

4.6

83

3.2

2.6

Tunisia

164

9.6

62

2.1

1.4

Uganda

241

21.8

113

3

2.8

United Republic of Tanzania

–

33.5

–

3.4

2.3

Asia

–

3,682.60

–

1.8

1.4

Sierra Leone Somalia

Togo

Afghanistan

652

22.7

41

6.7

2.9

Bangladesh

144

129.2

1,007

2.4

1.7

–

2.1

–

2.3

2.8

181

11.2

68

2.5

2.3

9,598

1,277.60

135

1.4

0.9

Republic of Korea

–

24

–

1.9

1.6

Hongkong, China

–

6.9

–

0.8

2.1

India

3,287

1,013.70

342

1.9

1.6

Indonesia

1,905

212.1

116

1.8

1.4

Islamic Republic of Iran

1,633

67.7

39

2.7

1.7

438

23.1

53

3.2

2.8

Israel

21

6.2

302

4.7

2.2

Japan

378

126.7

348

0.4

0.2

Jordan

89

6.7

55

3.4

3

Kuwait

18

2

111

–5.8

3.1

–

5.4

–

3

2.6

Lebanon

10

3.3

423

2

1.7

Malaysia

330

22.2

71

2.4

2

Mongolia

1,567

2.7

2

2.6

1.7

Myanmar

802

45.6

23

2.1

1.2

Nepal

147

23.9

161

2.5

2.4

Oman

212

2.5

11

3.6

3.3

Pakistan

796

156.5

179

2.7

2.8

Philippines

300

76

253

2.1

2.1

–

46.8

–

0.8

0.8

2,150

21.6

10

3.4

3.4

Bhutan Cambodia China Democratic People’s

Iraq

Democratic Republic of Laos

Republic of Korea Saudi Arabia 104

Fundamentals of Human Geography

Region/Country

Surface Area Population by (thousand the year 2000 sq km) (million)

Density of Population (per sq km)

Growth 1990–95

Rate 1995–2000

Singapore

1

3.6

6,587

1

1.4

Sri Lanka

66

18.8

300

1.3

1

Syrian Arab Republic

185

16.1

88

3.6

2.5

Thailand

513

61.4

119

1.3

0.9

Turkey

775

66.6

85

2

1.7

84

2.4

35

2.3

2

Vietnam

332

79.8

241

2

1.6

Yemen

528

18.1

33

3.5

3.7

Europe

–

728.9

–

0.3

0

Albania

29

3.1

124

0.8

–0.4

Austria

84

8.2

98

0.4

0.5

Belgium

30

10.2

331

0.1

0.1

United Arab Emirates

Bosnia & Herzegovina

51

4

78

–

3

111

8.2

74

–0.2

–0.7

–

4.5

–

–

–0.1

Czech Republic

79

10.2

133

–

–0.2

Denmark

43

5.3

126

0.2

0.3

Estonia

45

1.4

32

–0.2

–1.2

Finland

338

5.2

17

0.3

0.3

France

552

59.1

107

0.4

0.4

Germany

357

82.2

230

0.4

0.1

Greece

132

10.6

82

0.3

0.3

Bulgaria Croatia

Hungary

93

10

109

–0.2

–0.4

Ireland

70

3.7

55

–0.2

0.7

301

57.3

196

0.1

0

Latvia

65

2.4

38

–0.3

–1.5

Lithuania

65

3.7

57

0.2

–0.3

Republic of Yugoslavia)

26

2

80

–

0.6

Netherlands

42

15.8

470

0.7

0.4

Norway

324

4.5

15

0.5

0.5

Poland

323

38.8

127

0.3

0.1

Italy

Macedonia (Former

Portugal

92

9.9

109

0

0

Romania

238

22.3

97

0.3

–0.4

Slovakia

–

5.4

–

–

0.1

Slovenia

20

2

99

–

–0.1

Spain

506

39.6

79

0.2

0

Sweden

450

8.9

22

0.5

0.3

Appendix I

105

Region/Country

Switzerland

Surface Area Population by (thousand the year 2000 sq km) (million)

Density of Population (per sq km)

Growth 1990–95

Rate 1995–2000

41

7.4

182

0.7

0.7

United Kingdom

243

58.8

248

0.2

0.2

Yugoslavia

102

10.6

108

0.3

0.1

–

309.6

–

1.1

0.9

Canada

9,971

31.1

3

1.4

1

United States of America

9,629

278.4

31

1

0.8

–

30.4

–

1.5

1.3

7,741

18.9

2

1.4

1

–

0.2

–

–

2.1

New Zealand

271

3.9

14

0.9

1

Papua New Guinea

463

4.8

11

2.3

2.2

North America

Oceania Australia New Caledonia

Vanuatu

–

0.2

–

–

2.4

Latin America

–

519.1

–

1.8

1.6

2,780

37

14

1.2

1.3

–

0.2

–

–

2.4

Bolivia

1,099

8.3

8

2.4

2.3

Brazil

8,547

170.1

20

1.6

1.3

757

15.2

20

1.6

1.4

1,139

42.3

41

1.7

1.9

51

4

75

2.4

2.5

111

11.2

102

0.9

0.4

Argentina Belize

Chile Colombia Costa Rica Cuba Dominican Republic

49

8.5

173

2

1.7

284

12.6

46

2.3

2

EI Salvador

21

6.3

303

2.2

2

Guatemala

109

11.4

105

2.9

2.6

28

8.2

289

2

1.7

112

6.5

57

3

2.8

11

2.6

243

1

0.9

1,958

08.9

51

2.1

1.6

130

5.1

42

3.7

2.7

76

2.1

38

1.9

1.6

Ecuador

Haiti Honduras Jamaica Mexico Nicaragua Panama Paraguay

407

5.5

14

2.7

2.6

1,285

25.7

20

2

1.7

Puerto Rico

9

3.9

442

0.9

0.8

Trinidad and Tobago

5

1.3

254

1.1

0.5

Uruguay

176

3.3

19

0.6

0.7

Venezuela

912

24.2

27

2.1

2

Peru

106

Fundamentals of Human Geography

Appendix II Human Development Index, 2003 HDI Rank

Country

1.000 2.000 3.000 4.000 5.000

Norway Iceland Australia Luxembourg Canada

6.000 7.000 8.000 9.000 10.000

(HDI) Value

HDI Rank

Country

(HDI) Value

0.963 0.956 0.955 0.949 0.949

46.000 47.000 48.000 49.000 50.000

Uruguay Costa Rica Latvia Saint Kitts and Nevis Bahamas

0.840 0.838 0.836 0.834 0.832

Sweden Switzerland Ireland Belgium United States

0.949 0.947 0.946 0.945 0.944

51.000 52.000 53.000 54.000 55.000

Seychelles Cuba Mexico Tonga Bulgaria

0.821 0.817 0.814 0.810 0.808

11.000 12.000 13.000 14.000 15.000

Japan Netherlands Finland Denmark United Kingdom

0.943 0.943 0.941 0.941 0.939

56.000 57.000 58.000 59.000 60.000

Panama Trinidad and Tobago Libyan Arab Jamahiriya Macedonia, TFYR Antigua and Barbuda

0.804 0.801 0.799 0.797 0.797

16.000 17.000 18.000 19.000 20.000

France Austria Italy New Zealand Germany

0.938 0.936 0.934 0.933 0.930

61.000 62.000 63.000 64.000 65.000

Malaysia Russian Federation Brazil Romania Mauritius

0.796 0.795 0.792 0.792 0.791

21.000 22.000 23.000 24.000 25.000

Spain Hong Kong, China (SAR) Israel Greece Singapore

0.928 0.916 0.915 0.912 0.907

66.000 67.000 68.000 69.000 70.000

Grenada Belarus Bosnia and Herzegovina Colombia Dominica

0.787 0.786 0.786 0.785 0.783

26.000 27.000 28.000 29.000 30.000

Slovenia Portugal Republic of Korea Cyprus Barbados

0.904 0.904 0.901 0.891 0.878

71.000 72.000 73.000 74.000 75.000

Oman Albania Thailand Samoa (Western) Venezuela

0.781 0.780 0.778 0.776 0.772

31.000 32.000 33.000 34.000 35.000

Czech Republic Malta Brunei Darussalam Argentina Hungary

0.874 0.867 0.866 0.863 0.862

76.000 77.000 78.000 79.000 80.000

Saint Lucia Saudi Arabia Ukraine Peru Kazakhstan

0.772 0.772 0.766 0.762 0.761

36.000 37.000 38.000 39.000 40.000

Poland Chile Estonia Lithuania Qatar

0.858 0.854 0.853 0.852 0.849

81.000 82.000 83.000 84.000 85.000

Lebanon Ecuador Armenia Philippines China

0.759 0.759 0.759 0.758 0.755

41.000 42.000 43.000 44.000 45.000

United Arab Emirates Slovakia Bahrain Kuwait Croatia

0.849 0.849 0.846 0.844 0.841

86.000 87.000 88.000 89.000 90.000

Suriname Saint Vincent and the Grenadines Paraguay Tunisia Jordan

0.755 0.755 0.755 0.753 0.753

HDI Rank

Country

91.000 92.000 93.000 94.000 95.000

Belize Fiji Sri Lanka Turkey Dominican Republic

96.000 97.000 98.000 99.000 100.000

(HDI) Value

HDI Rank

Country

0.753 0.752 0.751 0.750 0.749

136.000 137.000 138.000 139.000 140.000

Nepal Papua New Guinea Ghana Bangladesh Timor-Leste

0.526 0.523 0.520 0.520 0.513

Maldives Turkmenistan Jamaica Islamic Republic of Iran Georgia

0.745 0.738 0.738 0.736 0.732

141.000 142.000 143.000 144.000 145.000

Sudan Congo Togo Uganda Zimbabwe

0.512 0.512 0.512 0.508 0.505

101.000 102.000 103.000 104.000 105.000

Azerbaijan Occupied Palestinian Territories Algeria El Salvador Cape Verde

0.729 0.729 0.722 0.722 0.721

146.000 147.000 148.000 149.000 150.000

Madagascar Swaziland Cameroon Lesotho Djibouti

0.499 0.498 0.497 0.497 0.495

106.000 107.000 108.000 109.000 110.000

Syrian Arab Republic Guyana Viet Nam Kyrgyzstan Indonesia

0.721 0.720 0.704 0.702 0.697

151.000 152.000 153.000 154.000 155.000

Yemen Mauritania Haiti Kenya Zambia

0.489 0.477 0.475 0.474 0.470

111.000 112.000 113.000 114.000 115.000

Uzbekistan Nicaragua Bolivia Mongolia Republic of Moldova

0.694 0.690 0.687 0.679 0.671

156.000 157.000 158.000 159.000 160.000

Guinea Senegal Nigeria Rwanda Angola

0.466 0.458 0.453 0.450 0.445

116.000 117.000 118.000 119.000 120.000

Honduras Guatemala Vanuatu Egypt South Africa

0.667 0.663 0.659 0.659 0.658

161.000 162.000 163.000 164.000 165.000

Eritrea Benin Côte d’Ivoire United Republic of Tanzania Malawi

0.444 0.431 0.420 0.418 0.404

121.000 122.000 123.000 124.000 125.000

Equatorial Guinea Tajikistan Gabon Morocco Namibia

0.655 0.652 0.635 0.631 0.627

166.000 167.000 168.000 169.000 170.000

Zambia Democratic Republic of Congo Mozambique Burundi Ethiopia

0.394 0.385 0.379 0.378 0.367

126.000 127.000 128.000 129.000 130.000

São Tomé and Principe India Solomon Islands Myanmar Cambodia

0.604 0.602 0.594 0.578 0.571

171.000 172.000 173.000 174.000 175.000

Central African Republic Guinea-Bissau Chad Mali Burkina Faso

0.355 0.348 0.341 0.333 0.317

131.000 132.000 133.000 134.000 135.000

Botswana Comoros Democratic Republic of Laos Bhutan Pakistan

0.565 0.547 0.545 0.536 0.527

176.000 177.000

Sierra Leone Nigeria

0.298 0.281

108

Fundamentals of Human Geography

(HDI) Value

All developing countries Least developed countries Arab States East Asia and the Pacific Latin America and the Caribbean South Asia Sub-Saharan Africa Central and Eastern Europe and the CIS OECD High-income OECD

0.694 0.518 0.679 0.768 0.797 0.628 0.515 0.802 0.892 0.911

High human development Medium human development Low human development

0.895 0.718 0.486

High income Middle income Low income

0.910

World

0.741

0.774 0.593

Notes : Aggregates of Education Indices are based on the aggregates of gross enrolment data calculated by the UNESCO Institute for Statistics and literacy data as used to calculate the HDI. Source : Calculated on the basis of data in columns 6-8 of Table 1 (HDR 2005); see technical note 1 for the details.

Appendix II

109

GLOSSARY Agriculture The science and art of cultivating the soil, raising crops and rearing livestock. It is also called farming. Balance of Trade The difference between the total value of a country’s exports and imports. An excess of export over import makes a favourable balance of trade, and the converse an unfavourable balance. Barter A direct exchange of excess produce between two parties to the mutual advantages of both, without the use of tokens, credit or money in the transaction. Census Official enumeration of population along with certain economic and social statistics in a given territory at some time interval. Chemical Fertilisers Substance of natural or artificial origin containing chemical elements such as phosphorus, potassium and nitrogem that are necessary to plan life. They are added to the soil for increasing its productivity. Contour Ploughing Tilling or ploughing hillsides or sloping lands along the contour lines, that is, around rather than up and down a slope mainly with a view to conserving soil and water. Crop Rotation Growing of different crops in succession on the same field from season to season to maintain soil fertility Dairy Farming A kind of agriculture in which major emphasis is on breeding and rearing milch cattle. Agriculture crops are raised mainly to feed these cattle. Density of Population The average number of inhabitants living within a specified unit of area, such as a sq km.

Dry Farming A method of farming adopted in certain regions of inadequate rainfall and devoid of irrigation facilities by conserving moisture in the soil and by raising drought-enduring crops. Economic Geography The aspect or branch of geography which deals with the influences of the environment, both physical and cultural, on the economic activity of man, bringing out similarities and differences from place to place in the ways people make a living.

Highway Public road connecting distant places. Such a road of national importance is called the national highway. Horticulture Cultivation of vegetables and fruits; often on small plots, involving higher intensiveness than in field cultivation. Imports Goods brought into a country from another country.

Environment Surroundings or the conditions under which a person or things exist and develop his or its character. It covers both physical and cultural elements.

Industrial Revolution The change in manufacturing from handoperated tools to power-driven machinery began in England during the middle of the eighteenth century.

Exports Goods despatched from one country to another.

Industry Systematic production characterised by division of labour and extensive use of machinery.

Extensive Agriculture Farming in which the amount of capital and labour applied to a given area is relatively small. Fazenda A coffee plantation in Brazil. Foreign Exchange The mechanism or process by which payments between any two places operating under different national currency systems are effected without passing of actual money or gold, etc. Freeways The wide highways on which cross-roads are avoided by providing overhead links where one turns in only one direction to ensure smooth and speedy traffic. Harbour An extensive stretch of deep water where vessels can anchor securely to obtain protection from sea and swell either through natural features or artificial works.

Intensive Agriculture Farming in which large amounts of capital and labour are applied per unit area of land, in order to obtain high yield. Inter Cropping It is a practice of growing two or more crops together on the same field in the same season International Trade Trade carried on between nations primarily to exchange their surpluses and make up their deficits. Metropolis A very large city or agglomeration of population in a district or a country, and is often the chief centre or seat of some form of activity— administrative, commercial or industrial. It generally serves a large hinterland. Mine An excavation made in the earth for digging out minerals such as coal, iron-ore

and precious stones. A mine usually denotes underground working except in open-pit mines.

practised mainly for subsistence, the modern ranches present an example of commercial pastoralism.

Mineral A substance that is found in the earth’s crust, and which generally has a definite chemical composition unlike most rocks.

Plantation Agriculture A large-scale one-crop farming resembling factory production. It is usually characterised by large estate, huge capital investment, and modern and scientific techniques of cultivation and trade.

Mineral Fuel Non-metallic minerals such as coal and petroleum which are used as fuel. Mineral Oil A mixture of hydrocarbons in solid, gaseous or liquid form found in the earth. It is commonly known as petroleum. It became a commercial product only in 1859. Mineral Ore Metals in their raw state as extracted from the earth. Mining An economic activity concerned with the extraction of commercially valuable minerals from the bowels of the earth.

Port The commercial part of a harbour containing facilities for embarking and disembarking passengers, loading and unloading, and some facilities for the storage of cargo. Primary Activity Activities concerned with collecting or making available materials, provided by nature, for example, agriculture, fishing, forestry, hunting or mining. Quarry An open-air excavation from which stone is obtained by cutting, blasting, etc.

Mixed Farming A type of farming in which cultivation of crops and raising of livestock go hand in hand. Both these activities play an important part in the economy.

Ranches Large stock farms, usually fenced in, where animals are bred and reared on a commercial scale. They are found especially in the United States.

Natural Resources Wealth supplied by nature-mineral deposits, soil fertility, timber, fuel, water, potential water-power, fish and wild life, etc.

Rotation of Crops A systematic succession of different crops on a given piece of land carried out in order to avoid exhaustion of the soil.

Nomadism A way of life of the people who are required to shift their dwellings frequently from place to place in search of pastures for their animals— the mainstay of their economy.

Secondary Activity Activities which transform the material provided by primary activities into commodities more directly useful to man.

Open-cast Mine A place where soil and its outward cover are first removed and a mineral or ore is extracted by quarrying. In a way, it is a quarry on a large scale. This method of mining is known as open-cast mining. Pastoralism An economy that solely depends upon animals. Whereas nomadic pastoralism is

Shifting Agriculture A method of farming in which a patch of ground is cultivated for a period of few years until the soil is partly exhausted or overrun by weeds, and after which the land is left to natural vegetation while cultivation is carried on elsewhere. In due course, the original patch of land is cultivated again when the natural growth has restored fertility. Subsistence Agriculture Farming in which its produce is mainly consumed in the farmer’s household unlike commercial agriculture whose products enter into trade on a very large scale. Transhumance A seasonal movement of herdsmen with their livestock and from and to the mountains or between the regions of differing climates. Transport The action of carrying persons and goods from one place to another. Truck Farming Growing of vegetables around the urban centres to meet the daily demand of the people is known as truck farming. It is governed by the distance a truck can cover overnight between the farm and the market. Urbanisation A general movement of people from small rural or agricultural communities or villages to larger towns engaged in varied activities such as government, trade, transport and manufacture. It also indicates the concentration of an increasing proportion of total population in towns and cities.

Sedentary Agriculture Farming practised more or less permanently on the same piece of land, the same as settled agriculture. Shaft Mine An underground excavation made deep into the earth for digging minerals like coal, precious stones and iron. Such mines contain vertical and inclined shafts and horizontal tunnels at various levels.

Glossary

111