Geology 11- Lecture Notes 1

Dear Class, These are the lecture notes as I have promised. Again, I have to stress that these are just from the slides and I cannot upload the figures since they do not belong to us. You have to look for some of the figures yourselves (they are usually found in textbooks, too). Maswerte kayo, I put some figures here. These notes do not and cannot in any way replace listening during the lecture in class. Napansin nyo naman siguro ang dami2x ko sinasabi na wala sa slides :) And the examples I cite are local so you also cannot find them in a basic geology book. For the concepts, though, the books are very helpful :) The point is, you may have these lecture notes BUT you are not assured of a high score in the exam. Listen and try to participate in the lecture and ask questions when things are not so clear. Disclaimer lang un hehehe. Ito na ang notes. Ayun, enjoy chickenjoy! ;)

Rakenrol, Ma’am Jill

Lecture 1 - Introduction to Geology GEOLOGY - study of the earth, its origin, history, materials, processes and resources Geology as a discipline: a. relevance of time, b. issue of scale, c. complexity of replicating natural systems in the laboratory Main Branches: 1. Physical - study of Earth materials and processes > Volcanology, Seismology, Environmental Geology, Engineering Geology, Mining Geology, Petroleum Geology, Mineralogy, Petrology, Geomorphology, Geophysics, Geochemistry, Planetary Geology

2. Historical - study of Earth origin and evolution > Paleontology, Stratigraphy, Geochronology Basic Concepts: 1. Catastrophism sudden, worldwide catastrophes are the agents of change that alter the physical features of the Earth over time widely accepted by theologians in the early 1800s due to similarity with Biblical events such as Noah’s Flood 1  Geology 11 ‐ Lecture Notes – Gabo (2008) 

2. Uniformitarianism proposed by James Hutton (The Father of Modern Geology) The present is the key to the past.” advocates the idea that the Earth is continuously modified by geologic processes that have always operated throughout time (at different rates), and that by studying them we can understand how the Earth has evolved through time Lecture 2 – The Planet Earth FORMATION OF THE EARTH – offshoot of the formation of the Universe Formation of the Universe: Big Bang Theory Formation of the Solar System: Nebular Hypothesis THE BIG BANG THEORY contends that the Universe originated from a cosmic explosion (origin unknown) that hurled matter in all directions 15 and 20 billion years ago first proposed by the Belgian priest Georges Lemaître in the 1920s Edwin Hubble justified Lemaître’s theory through observations that the Universe is continuously expanding; galaxies are moving away from each other THE NEBULAR HYPOTHESIS the solar system originated from a single rotating cloud of gas and dust, starting 4.6 billion years ago, which contracted due to gravity the idea was first proposed by Immanuel Kant and Pierre Simon de Laplace in the 18th century THE NEBULAR MODEL The Big Bang produced enormous amount of matter: rotating cloud of gas and dust. The rotating gas-dust cloud began to contract due to gravity. Most of the mass became concentrated at the center, forming the SUN. The remaining matter condensed to form the planets. THE SUN mostly made up of hydrogen, the principal product of the Big Bang 2  Geology 11 ‐ Lecture Notes – Gabo (2008) 

sun’s center became compressed enough to initiate nuclear reactions, consequently emitting light and energy (sun became a star) a middle-aged star THE PLANETS composition depended on distance from the sun planets nearest the sun contained high-temp minerals (e.g. iron) while those that are far away contained lower-temp materials (e.g. methane and ammonia, and some that contained water locked in their structures) Mercury, Venus, Earth, Mars - inner or terrestrial planets (nearest the sun) - rocky composition: largely silicate rocks and metals (Si, Fe, O) Jupiter Saturn Uranus Neptune - giant or Jovian planets (outer planets; far from the sun) - lack solid surfaces: in gaseous or liquid form - composition: light elements (H, He, Ar, C, O, Ni) Pluto - neither a terrestrial or Jovian planet - similar to the icy satellites of the Jovian planets SOME INTERESTING FACTS 1. Planets’ revolution = counterclockwise direction. 2. Planets’ rotation direction the same as direction of revolution except for Venus, which rotates in a retrograde direction. 3. Uranus and Pluto rotate about axes that are tipped nearly on their sides. 4. Orbital Speed of the Earth = 30 km/s THE EARTH - started as “dust ball” from the nebular gas and dust brought together by gravity (accretion), which was heated (heating) and eventually segregated into layers (differentiation) as it cooled - when cooling set in, the denser elements (e.g., iron) sank while the lighter ones floated out into the surface, creating a differentiated Earth

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CONSEQUENCES OF THE HEATING & DIFFERENTIATION OF THE EARTH 1. formation of atmosphere (mostly gases from volcanic activity) 2. formation of oceans (water released from crystal structure) * Life started when atmosphere was modified due to the appearance of the blue-green algae. THE EARTH’S VITAL STATISTICS Equatorial Radius = 6378 km Polar Radius = 6357 km Equatorial Circumference = 40076 km Polar Circumference = 40008 km Volume = 260,000,000,000 cu. miles Density = 5.52 g/cm3 CHEMICAL COMPOSITION (by mass) - 34.6% Iron, 29.5% Oxygen, 15.2% Silicon, 12.7% Magnesium SHAPE - Oblate spheroid (flattened at the poles and bulging at the equator) External Features of the Earth

1. Continents 2. Ocean basins Prominent Features of Continents

1. Mountains – elevated features of continents 2. Mountain ranges – chains of mountains 3. Mountain belts – mountain ranges that run across a vast area OCEAN BASINS - Oceanic ridges, Trenches, Seamounts/guyots, Abyssal hills/plains Internal Structure of the Earth >Crust 1. Oceanic – basaltic composition (SiMa); 3 to 15 km thick; density: ~3.0 g/cm3

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2. Continental – granitic composition (SiAl); 20 to 60 km thick; density:~2.7g/cm3 >Mantle – extends to a depth of ~2900 km (Fe, Mg)

1. Upper mantle – extends from the base of the crust 2. Mesosphere – lower mantle; from 660 km depth to the core-mantle boundary > Core – iron rich sphere with small amounts of Ni and other elements

1. Outer core – 2270 km thick; liquid 2. Inner core – solid sphere with a radius of 1216 km

*Discontinuities/Boundaries

1. Mohorovicic – crust – mantle 2. Gutenberg – core – mantle 3. Lehmann – outer core – inner core Question: How were these discontinuities discovered? Mechanical layers 1. Lithosphere

http://cache eb com/eb/image?id=73583&rendTypeId=35

a. Upper crust – brittle; 4-15 km depth b. Lower crust/uppermost mantle – ductile; 15 to 100 or 200 km depth 2. Asthenosphere – weak sphere; beneath the lithosphere and within the upper mantle 3. Mesosphere – solid, rocky layer ISOSTASY (it’s very important to understand this concept) from a Greek word meaning “same standing” basically concerned with the buoyancy of the blocks of the Earth’s crust as they rest on the mantle changes in the load over certain regions causes the lithosphere to make adjustments until isostatic equilibrium (i.e., neither rising or sinking) is reached AIRY’S THEORY (1) Mountains have “roots” which extend down into the mantle. Thus, elevation is proportional to the depth of the underlying “root”. 5  Geology 11 ‐ Lecture Notes – Gabo (2008) 

PRATT’S THEORY (2) Elevation is inversely proportional to density. Thus, the higher the mountain, the lower is its density; that is, light rocks “float” higher.

http://upload.wikimedia.org/wikipedia/commons/d/d3/Isostasy.Airy&Pratt.Scheme.png

HOW OLD IS THE EARTH? (estimates from different bases)

1. Cooling through conduction and radiation (Lord Kelvin, 1897): ~24 – 40 m.y. 2. rate of delivery of salt to oceans (John Joly, 1901): ~90 – 100 m.y. 3. thickness of total sedimentary record divided by average sedimentation rates (1910): ~1.6 b.y. 4. Amount of evolution of marine mollusks (Charles Lyell, 1800s): ~80 m.y. for the Cenozoic 5. radioactivity (Henri Becquerel, 1896): ~500 m.y. 6. Radiometric dating: 4.5 – 4.6 b.y. (which is, of course, the accepted age) Lecture 3 - MINERALS DEFINITION: Naturally occurring, Inorganic, Homogeneous, ,Solid, Definite chemical composition, Ordered internal structure MINERALOID - naturally occurring, inorganic material that is amorphous Ex. glass, opal POLYMORPHISM - ability of a specific chemical substance to crystallize in more than one configuration, which is dependent upon changes in temperature, pressure, or both PHYSICAL PROPERTIES OF MINERALS >Color - caused by the absorption, or lack of absorption, of various wavelengths of light >Streak - the color of a mineral in powdered form; not always identical to the color >Hardness – resistance of mineral to abrasion or scratching Mohs’ Scale of Hardness – 1. Talc; 2. Gypsum; 3. Calcite; 4. Fluorite; 5. Apatite; 6. Orthoclase; 7. Quartz; 8. Topaz; 9. Corundum; 10. Diamond >Crystal Form - the shapes and aggregates that a certain mineral is likely to form (look for pictures showing fibrous, platy, acicular, rhomboid, botryoidal, cubic, tabular, etc) 6  Geology 11 ‐ Lecture Notes – Gabo (2008) 

>Cleavage - the tendency of a mineral to break in particular directions due to zones of weakness in the crystal structure *Fractures or irregular breakages occur when bond strengths in a crystal structure is equal in all directions. >Luster - the ability of minerals to reflect light (e.g. vitreous, pearly, dull, metallic, etc) >Specific gravity - Ratio of volume of a substance and the weight of the same volume of water Other properties 1. Magnetism – ex. Magnetite (Fe3O4) 2. Fluorescence – ex. CaF2 3. Reaction to chemicals – ex. CaCO3 4. Taste – ex. NaCl 5. Odor – ex. S CLASSIFICATION OF MINERALS 1. Silicates 2. Non-silicates Bases for Classification 1. Composition • Single element (e.g. Cu, Au, S) • 2 elements (e.g. halite, pyrite) • Greater number of different kinds of atoms (e.g. KAl3Si3O10(OH)2) 2. Crystal Structure Relative Abundance of the Most Common Elements in the Crust ELEMENT

% BY WEIGHT

oxygen, O silicon, Si aluminum, Al iron, Fe calcium, Ca sodium, Na potassium, K magnesium, Mg all others

46.6 27.7 8.1 5 3.6 2.8 2.6 2.1 1.5

The Silicate Group largest group of minerals compounds containing silicon and oxygen building block: silicon tetrahedron (SiO4)-4 - structure possessing isolated silicate tetrahedra is called a nesosilicate. derived from the Greek word (nesogaean) that means "island". (e.g. olivine) - structure possessing double island silicate tetrahedra is called a sorosilicate. derived from a Greek word that means "group".

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- structure possessing parallel single chains of silicate tetrahedra is called an inosilicate (single chain or double chain). derived from a Greek word that means "chain". (e.g. pyroxene and amphibole) - structure possessing isolated rings of silicate tetrahedra, is called a cyclosilicate. derived from a Greek word that means "ring". - structure possessing parallel sheets of silicate tetrahedra is a phyllosilicate. derived from a Greek word that means "sheet". (e.g. micas) - structure possessing a three-dimensional framework of silicate tetrahedra is called a tectosilicate. (e.g. feldspar and quartz) The Non-Silicates 1. Native metals – gold, platinum, iron 2. Oxides – oxygen is combined with one or more metals (e.g. hematite, magnetite) 3. Sulfides – opaque with distinct colors (e.g. pyrite, galena) 4. Sulfates – SO4 (e.g. barite, anhydrite) 5. Carbonates – carbonate ion plus metal 6. Phosphates – PO4 (e.g. apatite) plus metal 7. Hydroxides – OH plus metal THE MOST COMMON ROCK-FORMING MINERALS Silicates: Quartz, feldspar (orthoclase and plagioclase), mica (biotite and muscovite), amphibole, pyroxene, olivine Non-silicates: Clay and Calcite Economic importance Non-renewable resource – processes that create the resources are so slow (takes millions of years to accumulate) Ores – useful metallic (and some nonmetallic) minerals that can be extracted and which contain useful substances 1. Mineral resources – sources of metals and other materials 2. Gemstones Lecture 4 – Igneous Rocks ROCKS What is a rock? • a naturally-occurring aggregate of one or more minerals; may or may not contain mineraloids, natural glass and organic matter. • Types of rocks vary based on composition, color, texture, structures, etc.

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http://www.washington.edu/uwired/outreach/teched/projects/web/rockteam/WebSite/rc

What are igneous rocks? • Ignis = fire • Formed from solidification of magma (intrusive) or lava which flows out from depths (extrusive) What is magma? • Molten material which may contain suspended crystals and dissolved volatiles (gases e.g. water vapor, CO2, SO2) • Molten rock composed of varying amounts of - Liquid; Silicate (sometimes carbonate or sulfide); Ions of K, Na, Fe, Ca, Mg, Al - Solid; Minerals; Rock fragments - Dissolved gas; H2O, CO2, SO2 • Temperature: 600-1200oC • Generated by increase in temperature, decrease in pressure and addition of volatiles Sources of heat for melting in the crust • original heat of the earth at the time of formation • some elements, e.g. U, produce heat through radioactive decay • heat transfer by conduction from a nearby body of magma • hot mantle plumes may upwell into the crust • frictional heat caused by rocks grinding past each other Origin and Formation of Magma Magma forms at: • Mid-Oceanic Ridges (MOR) – divergent boundaries • Subduction Zones – convergent boundaries 9  Geology 11 ‐ Lecture Notes – Gabo (2008) 

•

Hot spots – mantle plumes

Magma is classified according to: • Silica content - amount of SiO2 • Viscosity - resistance to flow • Temperature - temperature of melt formation Common Types of Magma Basaltic magma a. High density b. Low viscosity c. Relatively low silica content d. Crystallize at high temperatures (~1000 - 1200ºC) Granitic magma a. Low density b. High viscosity c. Relatively high silica content d. Crystallize at ~600ºC) basaltic (mafic) andesitic (intermediate) rhyolitic (felsic) Basaltic magma accounts for about 80 percent of all magma erupted by volcanoes. Rhyolitic and andesitic magma accounts for 10 percent each. Classification (chem’l composition) – Felsic, Silicic or acidic • >63% SiO2 – Intermediate • 52-63% SiO2 – Mafic or basic • 45-52% SiO2 – Ultramafic or ultrabasic •