Copy of 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