Geography Notes

 

The Earth and the Universe

Introduction Stars are not scattered regularly in the space; they occur in clusters which are called galaxies or nebulas. Milky Way, the earth’s galaxy contains about 100,000 million stars. Light takes about 4 years to reach earth, from the nearest star,  minutes from the sun and ! sec from the moon.  "he Solar System It consists of Sun and nine planets. It is formed by condensation of gases and lesser particles. #lanets re$ol$e in elliptical orbits around sun. "emperature of Sun at the surface is about 000 ! and at the core is about "0 million !. Sun is about #00,000 times big as the earth. %ercury $ It is Smallest and closest planet, only # million miles away from Sun. & year is of 'ust %% days. (enus) It is about *+ million miles approx.- away from sun. &lso, it is considered to be the Earth&s t'in because of similar sie, mass, density. /arth) It is about (# million miles away from Sun and has a satellite, the moon, which is about ",(%,(00 miles away and takes ") days to complete a re$olution around /arth while re$ol$ing eastwards anti)clockwise-. anti)clockwise-. %ars) It has dark patches and is expected to ha$e some plants.  0upiter) 1iggest planet. 2as circular light and dark band . %ade up of gases like  0upiter) hydrogen, helium and methane. 2as 1" satellites and is about 4+ million miles away from Sun. "emperature is about )!3 5. Saturn) Second biggest planet. 2as # rings and ( satellites around it. "akes "(*+ years to complete a year. 6ranus) 7aint bluish disc like when seen through a telescope. &round + times bigger and !+ times hea$ier than /arth with + satellites re$ol$ing around it. 8nly planet to re$ol$e from east to 'est around sun clock)wise direction-.  9eptune : Its disco$ery was the result of mathematical calculations calculations of their irregular irregul ar gra$itational eects on other planets. Similar to 6ranus but ha$ing only < satellites.

 

calculations of their irregular #luto) Its disco$ery was the result of mathematical calculations gra$itational eects on other planets. Smaller than /arth. =istance from Sun is > million miles during perihelion when it is closest from Sun- and 4,+>> million miles during aphelion when it is closest from Sun-.

 "he shape ? sie sie of the /arth It is geoid earth)shaped-. Euatorial circumference is about >.+ degree to the elliptic elliptic plane plane of re$olution- which causes this $ariation and causes seasons.

 

If axis were inclined at @ degree to the ecliptic, all parts of globe would experience eBual length of day and night.

 

9orthern hemisphere =uring 'inter =ecember-, the length of day decreases as we go northwards. &t the &rctic 5ircle >>.+ degree latitude-, there remains darkness for the whole day on ""nd .ecember. "he number of days with complete darkness increases as we go northwards and there remains darkness for half a year at the 9orth #ole. =uring summer 0une-, the conditions are 'ust re$erse. &t /rctic !ircle, there remains daylight for the whole day on "1st une. "he number of days with complete daylight increases as we mo$e northwards. In summer the area abo$e &rctic 5ircle is called 2and of the Mid3night -un&. &t the 9orth #ole, there is six months of continuous daylight.

Southern hemisphere 2ere, the conditions are 'ust re$erse. CinterD mid)winter in 9orthern hemisphere means summerD mid)summer in southern hemisphere and $ice $ersa.  "he altitude of mid)day mid)day Sun 1ecause of the inclination >>.+ degree-, the apparent altitude of mid)day sun $aries during a year. Sun is $ertically o$erhead at euator two times a year. "hose periods are called euinoxes, meaning eBual day and night.  "he times when sun sun is $ertically $ertically o$erhead at the the Tropic of cancer and Tropic of  !apricorn are called -ummer -olstice and Winter -olstice respecti$ely. =uring Summer Solstice, the day is longest in 9orthern hemisphere and during Cinter Solstice the day is longest in southern hemisphere.

 

 "ropics ropics mark mark the limits, abo$e abo$e which Sun is ne$er $ertically $ertically o$erhead. Eegions Eegions  " beyond tropics are marked by distinct seasons )summer, autumn, winter ? spring. Within the tropics, as the altitude of Sun does not change much during a year, the four seasons are indistinguishable. Length of day and night does not $aries much and is almost eBual within tropics. 4eyond /rctic and /ntarctic !ircle , it is always cold as sun is ne$er much high in the sky.

Seasonal changes and their eects on temperature =uring summer, Sun is higher in the sky and the rays of Sun fall nearly $ertically on the surface of earth causing heat to concentrate o$er small area. &lso, days are longer than nights in summer thus net heat is gained. &ll these factors lead to increase in temperature during summer. =uring 'inter, the conditions are re$ersed as the obliBue rays of sun spread o$er larger area and much of heat is initially absorbed by atmospheric impurities and water molecules. &lso, nights are longer than days. "hus, temperature is lowered.

 

=awn and twilight =awn) #eriod between sunrise and complete daylight.  "wilight)  " wilight) #eriod #eriod between sunset and and complete darkness. darkness.  "hese are caused caused as refracted refracted or diused rays rays of light of Sun reaches a region, when the Sun is actually below the horion. 9ear euator, the spans of both are short as the Sun rises and sets in nearly $ertical path. In temperate region, this span is longer as Sun rises and sets in obliBue path. &t the poles, these spans are still longer so that winter darkness is really twilight most of the time.

 

%athematical location of a place #arallels of Latitude) Set of lines running east and west, parallel to the eBuator. %eridians of Longitude) Set of lines running from north to south and passing through poles. Intersection of these gi$es location of any place on the globe. Latitude It is the angular distance of a point on earth’s surface, measured from the centre of the earth with respect to the eBuator, which lies in the middle of north and south poles. Lines of latitude are drawn at an inter$al of ! degree, which is sub)di$ided into > minutes precisely.and ! minute is further sub)di$ided into > seconds for locating any place  "he linear distance of a degree of latitude at poles are longer than at eBuator as the earth is a little Fattened near the poles. &t eBuator it is about >.* miles per degree and at poles, it is about >@.4 miles per degree. &n a$erage of >@ is used for distance calculatio calculation. n.  "ropic of 5ancer  "ropic 5ancer)) @.! miles at eBuator to  miles at poles. So, it is not freBuently used as a standard for distance calculation. some some facts are to be added-added

Longitude and "ime

 

Longitude is used to determine the 2ocal Time of an area in relation to the 9reen'ich Mean Time :9*M*T*;, which is also called World Time. /arth makes a rotation of 3> degrees in orest 'ooded mountain range- of Ehineland

 

 

2unsruck

(osages

Graben) •

East /frican 5ift Ialley, 3 miles long, stretching from East /frica through the 5ed -ea to -yria

(olcanic %ountain &lso called as mountains of accumulation.

 

Steps of formation) !. %olten materials are e?ected out of  =ssures  =ssures in earth’s crust. "hese materials are) • • • • • •

%olten la$a LiBuid mud &shes 5inders (olcanic bombs =usts

c ring of >re "his region region includes about about t'o3third of the world’s $olcanoes. "he chain of $olcanoes extends to about "000 miles. , people in the districts of Lisbon /ects of the earthBuake was felt within the @00 miles radius of Lisbon, in Borth /frica and Europe

 and earthBuake in -an >rancisco in !@> were also $ery disastrous.

 "he distribution of of earthBuakes) earthBuakes) Its distribution coincides $ery closely with that of volcanoes. "hough no part of the t he world can be said completely immune to earthBuakes. !. 5ircum)#aciAc areas)

 

General things) • •

&bout )0  of the world’s earthBuakes earthBuakes occur here It is region of greatest seismicity with most of the epicentres and freBuent occurrence along the 7aci=c 5ing of >ire

Seismicity 0 +he frequency or magnitude of magnitude of earthqua,es earthqua,es in  in a given area.

. (entifacts and =reikanter) Ientifacts)

 "hese are pebbles pebbles faceted smooth smooth surface createdcreated- by sand)blasting.  "hese are shaped shaped and polished by the wind abrasion abrasion to shape resembling 4raDil Buts. 7ormation) •

• •

&ngular rock fragments, mechanically 'eathered from mountains and rocks, are mo$ed by wind and are smoothened onupstanding 'ind'ard side  "hese pebbles with Fat surfaces- are are called (entifacts (entifacts Chen wind changes its direction, another facet is created. "hese are characterised by Fat facets with edges

.reikanter)

& (entifact with three 'ind3faceted surfaces is called =reikanter.  "hese faceted pebbles form .esert 7avements, a smooth mosaic like region co$ered with rock fragments and pebbles. *. =eFation hollows)

7ormation)

 

a. Cind lifts and blo' oK  unconsolidated  unconsolidated materials from the surface and depressions may be formed in this process b. 7aulting) • •

•

Minor3>aulting may create an initial shallow depression Eddying action of on)coming wind erodes the weaker rocks rocks until water table is reached Cater seeps out forming 6ases or s'amps in deFation hollows or depression

/xamples) a. >aiyum .epression in /gypt) !3 feet below the sea le$el b. Cestern 6S&) • •

Land was stripped of its natural vegetation co$er for farming =eFating action of winds blown o the unconsolidated materials as sand)storm, laying waste crops and creating what today is known 9reat .ust 4o'l

In dust storm, winds may lift dusts ! of feet high and carry them thousands of miles away.

Landforms of Cind =epositions in =eserts)  "hese are formed formed when winds deposits the materials materials being carried carried by them. "he distance to which the materials can be carried depends greatly on their coarseness. >ine dusts) •

•

 "hese are lighter lighter and may be transported transported out of the deserts limits and deposited somewhere else Sometimes these tra$el as far as "#00 miles

/xamples) •

=usts from -ahara .esert sometimes crosses the  Mediterranean and fall o$er Italy as Ublood rain’ or o$er glaciers

of Switerland

 

•

=ust that settles in G'ang Go basin while coming from 9obi desert has accumulated to a depth of se$eral hundred miles o$er centuries

5oarser materials) • •

 "hese are hea$y, hea$y, so are not transported out of the the desert limits  "hese form $arious $arious depositional depositional features such such as dunes, etc within the desert limits

 "hese landforms landforms are rarely static and their migration pattern depends on) • • •

-iDe of the particles being carried by them .irection and the $elocity of the wind Location and nature of the surface o$er which the particles are being carried and the presence or absence of 'ater and vegetation

Some ma'or features are as follows) !. =unes)  "hese are hills of sands formed as a result of depositional action of wind and are imparted characteristic shape as per the direction and $elocity of winds. 1asic types) a. 2ive dune) "hese are in continuous motion b. >ixed dunes) "hese are rooted 'ith vegetation and do not mo$e  "hese are best best represented represented in Erg deserts where sea of sands are continuously mo$ed, reshaped and re)deposited forming a $ariety of features. 1ased on sie, shape and alignment $arious types are as follows) • •

•

Star dunes #arabolic #arabo lic blow)out dunes &ttached or head dune

• •

 "ail dune  "ail Lateral dune

 

• • • • • • •

Sword dune #yramidal dune Cake dune Smoking dune 2airpin dune  "rans$erse  " rans$erse dune &d$anced dune

 "wo  " wo most common dunes) a. 1archans) 7ormation) •

•

Sometimes sands are accumulated o$er some obstacle, such as a patch of grass or a heap of stones  "hese occur transversely to the wind, so frictional retardation retardation is minimum at the edges because of which horns thin out and are lowered by the action of pre$aili pre$ailing ng wind forming a crescent shaped structure

&d$ancement) •

• • •

Sands are dri$en up the windward the windward side by the action of pre$ailing wind till these reaches the crest &fter reaching the crest, the sands slips do'n the leeward side In this way, the dune ad$ances 5ate of ad$ancement $aries from feet below the earth surface

•

CorldVs lowest Lake

Lakes formed by glaciation) !. 5irBue lakes or tarns) It is arm)chair shaped lake formed as result of glaciation details in the ch. Glaciers/xamples) •

Eed tarn) /nglish Lake =istrict Eibbon lakes) lakes) "hese are formed by accumulation of water in the glacial trough, and are long and deep •

Lake 6llswater