Geol 11 LE REVIEWER PDF

Introduction to Geology Definition of Geology - Geo + logos (greek): meaning earth + study/discourse of - Study of earth and other extraterrestrial bodies; its form, composition, and processes it has undergone and is undergoing Geology as a Discipline 1. Relevance of time...

Introduction to Geology Definition of Geology - Geo + logos (greek): meaning earth + study/discourse of - Study of earth and other extraterrestrial bodies; its form, composition, and processes it has undergone and is undergoing Geology as a Discipline 1. Relevance of time a. “geologic”/deep time: all events are relative to each other against time 2. Issue of scale a. Small vs large b. Micro vs macro c. Local vs regional 3. Complexity of replicating natural phenomena a. Simplified models Branches of Geology 1. Physical geology: examines earth’s rocks and minerals, understands processes that operate beneath or on the surface a. Mineralogy b. Petrology c. Volcanology d. Structural geology e. Seismology f. Environmental geology g. Engineering geology h. Mining geology i. Petroleum geology j. Geomorphology k. Planetary geology 2. Historical geology: origin and evolution of earth through time a. Paleontology b. Stratigraphy c. Geochronology Early Schools of Thought 1. Catastrophism a. Baron Georges Cuvier, 16th century b. Sudden worldwide catastrophes are agents that alter the physical features of the earth and it remains unchanged c. Widely believed by theologians in the 1800s due to similarity with biblical events 2. Uniformitarianism a. James Hutton (father of modern geology), 18th century  b. Earth is continuously modified by geological processes that have always operated at different rates i. “Present is key to the past”, popularized by Charles Lyell ii. Principles of Geology 1. Actualism: earth has been around for a very long time The Universe and the Earth Formation of the Universe and the Earth Singularity - An infinitely small region of space with zero volume and no dimensions - State of universe before Big Bang Big Bang Theory - Georges Lemaitre, 1920s - 13.8 billion years ago - Superfast inflation or expansion in 3 dimensions Evidence of Big Bang 1. Abundance of primordial elements (H and He) 2. Cosmic microwave background radiation (CMB) a. 1965, astronomers tried to eliminate the background noise from satellite signals b. Leftover radiation from the energy-rich big bang 3. Hubble’s Law a. 1929, Edwin hubble observed a redshift: stretching of wavelength when a light source moves away from the observer Observable Universe - Present diameter: 93 billion light years - Rate of expansion: 1.96 million km/s The Nebular Hypothesis - Immanuel Kant and Pierre Simon de Laplace, 18th century - Rotating gas-dust cloud began to contract due to gravity - Most mass in the center: sun > remaining matter > asteroid > planetesimals > planets Nucleosynthesis - Formation of new elements due to fusion of sun and stars - Creates new atomic nuclei from preexisting nucleons, primarily protons and neutrons - Supernova: explosion of star, when star burns its H and He fuel, it will collapse into itself and then rapidly rebound outwards Protosun and the Planets 1. Terrestrial Planets: rocky composition, large, silicate rocks and metals 2. Jovian Planets: gaseous or liquid form, composed of light elements The Iron Catastrophe - Formation of differentiated earth 1. Accretion: sticking together of dust due to gravity; proto-earth: dust ball 2. Heating: melting of materials; molten earth 3. Differentiation: sinking of heavy elements, rising of light elements; differentiated earth Sources of Heat 1. Collision 2. Solar radiation 3. Radioactive Heat 4. Temperature increase from contraction Giant Impact Hypothesis - Collision of earth with mars-sizes planetesimal to form the moon Formation of Atmosphere - Formed by heating and differentiation - 4.5 Ga, primordial gases lost to space due to solar winds - 4.0 Ga, volcanic venting, and icy comets release gases - 3.5 Ga, blue green algae convert carbon dioxide to oxygen Layers of the Earth Layering by Chemical Composition 1. Core a. Fe-rich with small amounts of Ni 2. Mantle a. Fe-rich but diluted with O, Si, Mg 3. Crust a. Solid outer shell Layering by Mechanical Properties 1. Inner core: solid 2. Outer core: liquid 3. Lower mantle: solid 4. Asthenosphere: liquid but mobile 5. Lithosphere: liquid and rigid a. Cause: response of each layer to a dominant variable at certain depths b. Temperature increase: melting  c. Pressure increase: solidification Evidence of Earth Layering 1. Seismic waves a. P-waves: solid and liquid medium b. S-waves: solid medium c. Shadow zones: no waves/certain waves recorded 2. Xenoliths a. Mantle rocks entrained by ascending magma brought up to the surface 3. Abundance of Fe in Solar System 4. Earth’s magnetic field a. Generated by the flow of the liquid outer core Theories of Isostasy Isostasy - Equilibrium between lithosphere and asthenosphere - Explains why topographic differences exist 1. Pratt’s Theory a. Equal depth of lithosphere b. Elevation differences due to density c. High density (lower), low density (higher) 2. Airy’s Theory a. Equal density b. Elevation differences due to depth of roots c. Deep root (higher), shallow root (lower) 3. Flexural Theory a. Elasticity of lithosphere b. Local load to regional downwarping, example is ice sheets Size of Earth Eratosthenes - 240 BC, first to measure the earth’s circumference using the pole at alexandria and well at syene - Actual circumference - Equatorial: 40 076km - Polar: 40 008km Earth’s Large Scale Features 1. Continents a. Mountain Belts: bands of high elevation above sea level b. Plains: extensive areas of low elevation above sea level 2. Ocean Basins  a. Mid-oceanic Ridges: extensive ranges of high elevation below sea level b. Trenches: deep regions of ocean floor, formed in subduction zones c. Abyssal Plains Continental Margin Features - Landforms in the transition zone between continents and ocean basins - Continental shelf - Continental slope - Continental rise Seafloor Features 1. Abyssal plains: bast, flat expanse of ocean floor 2. Seamounts: submarine volcanic landforms 3. Guyots: underwater plateaus from inactive seamounts Plate Tectonics Continental Drift Hypothesis - Alfred Wegener - Pangaea: “all land” supercontinent, divided to Laurasia (North America, Asia, Europe) and Gondwanaland (South America, India, Australia, Africa, Antarctica) - Panthalassa: “all sea” Evidence for the Continental Drift 1. Continental jigsaw puzzle fit a. Observed when world maps were available b. Coastlines of continents roughly fit together, like south america and africa c. Continental shelf was observed to better observe and and avoid wave erosion and depositional processes 2. Fossils match across oceans a. Mesosaurus b. Glossopteris c. Lystrosaurus 3. Rock type and geologic features a. Similar rock type in age and structures like the Appalachian-Caledonian mountains 4. Paleoclimate a. Coal seams in northern hemisphere wit tropical trees b. Glacial till and striations in south africa, south america, australia, india Opposition for the continental drift - Two mechanisms for continent movement were not accepted: - Gravitational forces of the sun and moon - Large continent break through the thin ocean floor Seafloor Spreading - Harry Hess, introduced in the 1960s - Extensive mapping of ocean floor during world war 2, led to the discovery of ocean basins - Ocean drilling - Earth’s crust is moving away from mid oceanic ridges - New material is formed along mid oceanic ridges Additional evidence for plate motion 1. Paleomagnetism and polar wandering a. Curie point: temperature at which a mineral changes its magnetic properties b. Paleomagnetism: small magnetite minerals point to their magnetic north during formation 2. Magnetic reversals a. Magnetic strips on the ocean floor b. Magnetic polarity 3. Hotspot volcanism a. Localized, long lasting hot regions below the lithosphere b. Frame of reference for tracking plate motion c. Age corresponds to the time it was on top of the mantle plume 4. Seismicity and plate boundaries a. Deep earthquakes: at subducting slabs b. Shallow earthquakes: regions of rifting Plate tectonics theory - Unifying theory of geology - Lithosphere is composed of tectonic plates in constant motion relative to each other Major plates: 1. Pacific 2. North American 3. Eurasian 4. African 5. Antarctic 6. Indo-Australian 7. South American Plate Boundaries - Where most movement occurs 1. Divergent a. Constructive b. Plates move apart, creates oceanic crust as seafloor i. Continental rifts and oceanic ridges are the spreading centers ii. East african rift, mid-atlantic ridge  2. Convergent a. Destructive b. Plates move towards each other c. Forms subduction zones when oceanic lithosphere is involved i. Oceanic vs continental: due to density differences, forms volcanic arcs ii. Oceanic vs oceanic: due to density differences, forms island arcs iii. Continental vs continental: forms collision zone, due to buoyant plates, subduction interface, forms mountain belts 3. Transform a. Conservative b. Plates grind past each other c. Connects oceanic ridges into a continuous network Mechanisms for Plate Motion 1. Mantle Convection: main mechanism; due to temperature and density differences a. Others: i. Ridge Push: divergent ii. Slab Pull: convergent iii. Mantle Drag: resists plate subduction Philippine Tectonics - Volcanism - Earthquakes - Convergence - Plates - Eurasian plate - Philippine mobile belt - Philippine sea plate - Trenches - West - Manila trench - Sulu-negros trench - Cotabato trench - East - East luzon trench - Philippine trench Minerals Mineral - Naturally occurring - Inorganic - Homogenous solid - Definite chemical composition  - Ordered internal structure 1. Naturally occurring a. Natural, geologic processes, not man made b. Crystallization of magma c. Precipitation of hydrothermal fluids d. Evaporation of seawater 2. Inorganic a. Not composed of organic molecules (C-H bonds) b. Can include materials formed via biological processes 3. Homogeneous solid 4. Definite chemical composition a. Represented by a chemical formula 5. Ordered internal structure a. Crystalline b. Regular, orderly arrangement of ions Mineraloids - Amorphous: internal structure is not crystalline Polymorphism - “Many forms” - Ability of chemical substance to recrystallize in more than one configuration - Depends on formation conditions such as temperature and pressure Rock - More loosely defined than minerals - Solid consisting of minerals, preexisting rocks, mineral-like matter 1. Rocks composed of minerals a. Monominerallic b. Aggregate of minerals 2. Pieces of preexisting rocks a. Found in sedimentary rocks 3. Mass of mineral-like matter a. Non-mineral matter like obsidian b. Organic debris like coal Physical properties of minerals 1. Color: caused by absorption, reflection, transmission of light a. Idiochromatic minerals: occur in shades of one particular color; diagnostic property b. Allochromatic minerals: has a range of colors due to impurities and chemical substitution  2. Diaphaneity: degree of transparency or opacity, describes the amount of light being transmitted a. Transparent b. Translucent c. Opaque 3. Luster: ability of minerals to reflect light a. Metallic b. Non-metallic 4. Streak: color of substance in powdered form; true color, streak is constant, diagnostic property 5. Hardness: resistance to abrasion or scratching, function of the type and strength of the chemical bonds present; diagnostic property 6. Cleavage: tendency of mineral to break along planes of weak bonding a. Fracture: irregular breakages due to equal bond strengths; no preferred planes of weakness 7. Habit: shapes and aggregates that a certain mineral is likely to form a. Characteristic shape of: i. Individual crystal ii. Aggregates of crystal b. Single mineral can have different habits c. Some habits are distinct to certain minerals 8. Other properties a. Magnetism b. Fluorescence c. Reaction to chemicals d. Taste e. Odor Minerals in Number - 4,000 minerals identified - Only a few dozen abundant make up most of the earth’s crust; rock forming minerals - Si and O are the most abundant elements in the crust Mineral Classification 1. Silicates a. 90% of earth’s crust, more than 800 known 2. Non-silicates a. Most of economic minerals b. 8% of earth’s crust Silicon-oxygen tetrahedron - Basic building block - Structures: - Sheets  - Chains - 3d structures 1. Silicates a. Nesosilicates b. Inosilicates i. Single chains ii. Double chains c. Phyllosilicates d. Tectosilicates 2. Non-silicates a. Carbonate i. Calcite 1. Limestone: building stone, cement 2. Marble: building ii. Dolomite: source of Mg metal b. Sulfates i. Gypsum: dentistry, plaster ii. Barite: liquid contrast c. Sulfides i. Pyrite: fool’s gold ii. Galena: lead ore d. Oxides i. Magnetite: iron ore for steel manufacture ii. Hematite: red pigment e. Halides i. Fluoride 1. Fluorite: flux in steel manufacture ii. Chloride 1. Halite: cooking f. Native metals i. Gold: currency ii. Copper: electronics, construction