Geology Exam 3 Study Guide
Geology Exam 3 Study Guide GEO 101
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Popular in Geology
This 7 page Study Guide was uploaded by Carter Cox on Tuesday March 22, 2016. The Study Guide belongs to GEO 101 at University of Alabama - Tuscaloosa taught by Keene in Spring2015. Since its upload, it has received 41 views. For similar materials see Dynamic Earth in Geology at University of Alabama - Tuscaloosa.
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Date Created: 03/22/16
Geo 101 – The Dynamic Earth Exam 3 Study Guide THIS IS NOT ALL INCLUSIVE – What is the significance of a sedimentary basin? They are the location of most of the earths hydrocarbon reserve What do transgressions and regressions tell us? Transgressions are when sea level rise – shoreline migrates inland Regression is when sea levels fall coast migrates seaward Why does sea level change? Ecstatic – global sea level change o Sedimentary local variation from accumulation and/ or compaction of sediment o Tectonic continents and/ or sea floor rising and falling How are diagenesis and metamorphism related to each other and what causes each? Digenesis As temperature and pressure increase still in deeper in the subsurface, the changes that take place in the rocks on more profound. At a high temperature and pressure metamorphism begins and make new mineral s The transition between metamorphism and diagenesis occurs between 150 and 300 degrees Celsius What kinds of changes occur during metamorphism? Recrystallization Same mineral, different size and shape of grains Changes the size and shape of grains without changing the identity of the mineral Phase Change Same chemical composition Transforms one mineral into another mineral with the same composition but a different crystal structure Neocrystallization New minerals Growth of new mineral crystals that differ from those of the protolith (Clay and Quartz) turn into (quarts garnet and mica) Pressure solution (Must be in Water) Minerals change shape – elongate Wet rock is squeezed more strongly in one direction than in others. Mineral grains dissolve where their surfaces are pressed against other grains Plastic deformation Happens when a rock is squeezed or sheared at elevated temps and pressures. Under these conditions grains behave like soft plastic and change shape without breaking How do geologists classify metamorphic rocks? Parent Rocks o Component minerals Sandstone Quartzite Shale – slate Limestone marble Texture o Foliated layer or stripes forms by rotation or recrystallization o Nonfoliated o Shape, size, and arrangement of grains What causes foliation? Foliation layer or stripes o Forms by rotation and recrystallization What does metamorphic grade tell us? Degree of metamorphic change What do metamorphic facies and index minerals tell us? Metamorphic facies o Group of minerals that are created under specific temperatures and pressures Index Mineral o Tells what forms with specific temperature and pressures Where does metamorphism happen? Contact Metamorphism o Existing rock heated by intruding magma o Low grade metamorphism Regional Metamorphism o Associated with mountain building Burial o Very deeply buried sediment Dynamic o Fault Zones Subduction Zones o High pressure and low temperature Shocks o Meteorite impact What is the rock cycle? Series of processes in which rock forms; Any type of rock can be reformed into any other type of rock What causes earthquakes? Movement of magma Volcanic explosion Giant landslides Water pumping or injection Underground nuclear bomb tests Plate tectonics o New fault or old fault Know the major types of faults, the subcategories under each, what kind of movement occurs at each fault type, and why that particular type of movement occurs with that fault. Dip slip o Normal – occur where there is tension or stretching of Earths crust o Reverse Thrust compression (opposite of normal), pops up (mountains), much steeper o Oblique extension or shorting (moves in two directions at once) Strike Slip o Left Lateral o Right Lateral What is elastic rebound theory and what does it explain? Idea that earth can take a certain amount of pressure o Has a certain breaking point like a twig snapping in half What are the kinds of displacement that occur along faults? how far each side of fault moves away from each other o Fault Creep moves a little bit everyday o Periodic Energy Release earth is moving and pressure builds o Store up energy Be able to explain foreshock, aftershock and earthquake triggering. Foreshock fault is beginning to move Aftershock fault is adjusting to the new position Earthquake Triggering more earthquakes outside aftershock area o Hanging wall rock is above fault o Foot wall rock is below fault What are the types of seismic waves and their characteristics? Body Wave travels through the Earth o P Right to left o S Up and down o P waves Compressional waves Particle motion is parallel to the wave direction Can go through outer core o S Waves Shear wave Particle motion is perpendicular to the wave direction Cant move through outer core o Each wave changes velocity depending what they are going through Surface Wave o Love Wave Moves like a snake (side to side particle motion) Deeper you go the less motion o Rayleigh Waves Make a lot of damage, creates most shaking during quake Up, back, around Counter clockwise elliptical particle motion How are earthquakes recorded, measured, and located? Seismograph o Measures intensity, direction and duration of an earthquake Seismograms o Record of ground motion as function of time Primary wave 1 t nd Shear 2 Locating o P waves are faster than S waves Determine difference (sp) Distance 8(sp) Earthquake size o Magnitude Measure energy release o Intensity Look at damage (centered around humans) o Which earthquake magnitude measurement scale is considered the most accurate? Why? Richter o Uses Maximum amplitude of S wave S P time Good for shallow local quakes Mercalli o Based on human experience o Measures damage to humans and their structures Most Accurate o Moment Magnitude Uses Several wave types Rock properties Area of fault Amount of slip Where do earthquakes occur, and where will you find shallow or deep earthquakes? occur around all of the plate boundaries Deep o Subduction Zones Shallow o Divergent Plate Boundaries Normal fault o Continental Rift Zone Normal fault o Continental collision Zone Reverse and thrust (compression) o Convergent Plate Boundaries Normal and thrust faults o Transform Strike slip fault Center of plate o Rare – 5% o NOT FULLY understood earthquake How and why does each earthquake hazard happen and what are the results? Ground shaking – amount of damage is determined by shaking o Ground Displacement o Land slide movement of rock and sediment downslope o Liquefaction mixing of soil and ground water o Fire stoves, gas, electrical line rupture o Tsunami wide wave (large volume) 500 MPH can predict only hours o Disease no clean water, sewage spilling, no transportation Can earthquakes be predicted? What can we do to mitigate the damage? Not really o Can be predicted where but not when To mitigate damages o Monitory USGS Maps o Early Warning Systems o Being Prepared o Construction Techniques What are the factors that determine the kind of deformation that will take place? Type of rock Temperature Pressure Rate of deformation Which geologic features are caused by deformation? What are their characteristics? Faults brittle Joint brittle o Natural cracks no opposing movements o Veins minerals precipitate in joints Folds ductile o Compressive strain o Anticline o Syncline o Monocline stair step o Plunging asymmetrical o Nonplunging symmetrical o Basin bowl oldest is on the edge o Dome oldest in the center What information does a geologist get from strike and dip? Strike o Compass direction of outcrop Angle relative to north (measured clockwise) Dip o Perpendicular to strike Measures amount and direction of tilt What happens at each place where orogenies occur? A mountain building event o Subduction Zone Oceanic plate pushes into another creating a mountain o Continental Collision Two plates meet in the middle and crumple up Deforming each other Example: Himalayas o Continental Rifting Stretching, faulting, and volcanoes o What is isostasy? Lithosphere “floats” on asthenosphere o Gravity pulls down lithosphere Idea that earth is always in equilibrium o Squeeze in one place and another place pops out What is a craton? What are the parts of a craton? craton: crust that hasn’t experienced an orogeny for at least 1 billion years, center/ Parts: o Shield Precambrian Exposed rocks o Platform Precambrian Rocks covered by sediment
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