Midterm 3 Study Guide
Midterm 3 Study Guide GEOL 120
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This 10 page Study Guide was uploaded by KDeRoche92 on Tuesday March 29, 2016. The Study Guide belongs to GEOL 120 at Colorado State University taught by Bryan, Sean in Summer 2015. Since its upload, it has received 64 views. For similar materials see Exploring Earth: Physical Geology (GT-SC2) in Biology at Colorado State University.
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Date Created: 03/29/16
STUDY GUIDE FOR MIDTERM 3: ALL THE QUESTIONS FROM “WHAT TO KNOW” ANSWERED How do rocks break down? What are the differences between mechanical (physical) weathering and chemical weathering? Weathering is the process of rocks breaking down. Physical weathering is done by wind, water, sun, temperature change. Chemical weathering, such as Hydrolysis and Oxidation, dissolves and seeps into the rock. A good example is acid rain. What are the typical products of weathering? Products of weathering = sediment. From sand to boulders sediment is a direct result of weathering and the main component of sedimentary rocks. How are sedimentary rocks formed? What are they made up of? Sedimentary rocks are formed from deposited sediment. This sediment can be plant material parts of other rocks animal parts etc. What is the difference between clastic, chemical and biochemical sedimentary rocks? Clastic = sedimentary rocks made by natural processes Chemical = sedimentary rocks made by evaporation or precipitation of minerals Biochemical = living organisms produce the sediment and this organic process forms the rock. How does the size of clasts affect the transport and deposition of those clasts? Abrasion can reduce the size of the grain size. Small sizes transported easier and larger sizes deposited easier. Grain size of a clast determines the name of rock/ mineral. How can we relate the characteristics of a sedimentary rock to the environment in which it was deposited? A high energy environment can transport clasts which (depending on their shape and size) will be deposited when the energy reaches the threshold where they can no longer be transported. So we can expect lower energy environments to have smaller clasts in sedimentary rocks and higher energy to have larger. What is bedding in sedimentary rocks? Bedding is just sediment being deposited. What does cross-bedding indicate? Cross-bedding can indicate high wind, or water movement. This is horizontal beds on a sedimentary rock. Describe what happens during chemical and physical weathering. Know the difference between chemical and physical weathering. Chemical weathering—oxidation, hydrolysis. Dissolving of rock material. Physical weathering—erosion by wind, water, and other natural processes. Determine which minerals are most resistant to weathering (quartz) and which are least resistant to weathering (mafic minerals). quartz, olivine, orthoclase and plagioclase, pyroxene and amphibole, dolomite, calcite, biotite, muscovite (most resistant to least) Define the three main categories of sedimentary rocks (clastic, chemical, biochemical). If given a description of a rock, determine which category it would go in. Chemical Biochemical Clastic How do metamorphic rocks form? They are physically and chemically transformed due to changing temperature or pressure. They were never “melted” because if they were they would be igneous. High pressure and temperatures recrystallize and form bigger minerals changing the chemical structure of the original rock. What role do parent rock composition, temperature, pressure and fluids play in metamorphism? Parent rock/material determines which type of metaphoric rock forms; Pressure affects crystal size. Shallow levels= rock fractures=low temp/pressure=mineral unaffected Deep levels= rock flows= temp/pressure high=mineral can recrystallize=metamorphic. How are metamorphic rocks classified? Composition and texture tell us what metamorphic rock. What is foliation in metamorphic rocks? Foliation is repetitive layering of metamorphic rocks. Can be paper thin or very this layers. What does metamorphic grade mean? Temperature and pressure conditions: What is the difference between regional metamorphism and contact metamorphism? Contact metamorphism occurs close to igneous intrusions—low pressure + high temperature. Magma heating surrounding rocks (only heating) Regional metamorphism (forms slates, schist, gneiss) occurs over large areas. Compressive stress along folds a lot of the time. Fluids, stress (can have temp increase pressure. What is stress? Stress is force per area; Force is push/pull expressed as amount of acceleration *Confining Pressuresame amount of stress in all directions *Differential pressure more/less stress in one direction. Strength of the rock determines how much stress is necessary to deform it as well as the rocks depth in the crust. What is an anticline and syncline? Anticline“A” shaped fold Syncline“U” shaped fold, more wavy What is a fault? What is the motion on a normal, reverse, and strikeslip fault? A fault is a fracture where one side is slipped past the other. Footwall Hanging Wall A normal fault the hanging wall slips past footwall. Reverse fault the footwall slips above hanging wall (switch arrows) A strikeslip means instead of moving up or down they move past each other right and left. Define the difference between brittle and ductile deformation. Determine whether an example of deformation is brittle or ductile. (i.e. folds, faults, joints, etc.) Brittle deformation=crack where rock is pulled apart=JOINT Fracture where one side is slipped past the other = FAULT Determine the type of fault that would occur from different types of stress (i.e. compression, tension and shear). COMPRESSION—REVERSE TENSION—NORMAL SHEAR—STRIKE SLIP Describe the characteristics of slate, schist, gneiss, quartzite, and marble. Be able to identify them from a description and picture. GNEISS-FOLIATED Put these metamorphic rocks in order from lowest metamorphic grade to highest metamorphic grade: slate, phyllite, schist, gneiss. PICTURE ABOVE Predict the type of stress (compression, tension or shear) that would occur at different tectonic settings (rifting, seafloor spreading, transform boundaries, subduction zones and continental collisions). RIFTING—COMPRESSION SEAFLOOR SPREADING—TENSION TRANSFORM—SHEARING SUBDUCTION—COMPRESSION CONT. COLLISIONS—COMPRESSION Determine how a change in the thickness, density, or temperature of the crust would affect regional elevations. SHALLOW LEVELS ROCK FRACTURES, LOW TEMP AND PRESSURE DEEP LEVELS ROCK FLOWS, HIGH TEMP AND PRESSURE CONTINENTAL COLLISIONTHICK CRUSTCOMPRESSION MANTLE UPWELLINGHOT SPOT, CONTINENTAL RIFT SUBDUCTION ZONE, ADDING MATERIAL, HEATING CONVERGENCE=REVERSE FAULTING Igneous and metamorphic rocks @ high elevation, Reverse faulting caused by compression thicker crust higher elevation. Define relief and describe two ways the high relief can be created. Relief Difference between the highest point of elevation and the lowest. EARTHQUAKES Where do earthquakes occur? Along faults. What happens during an earthquake? Energy is released where faults move. What the main types of seismic waves? Which waves travel fastest? SWaves, PWaves, Surface Waves. PWaves move the fastest What is the hypocenter and epicenter of an earthquake? Hypocenter refers to the spot the earthquake actually begins. The epicenter is directly above the hypocenter one earth’s surface. What is the difference between earthquake magnitude and intensity? Magnitude is a measure of the energy released. Intensity is a measure of what is felt. List the three main types of seismic waves (P, S, surface) and describe the way each wave travels (i.e. compression, shear). S waves travel through shear, P waves can travel through compression (&any kind of material) Describe the changes (i.e. buildup and release) in stress on a fault before, during and after an earthquake. Friction keeps rock from moving but becomes can have enough built up stress to slip causing an earthquake and is then that energy is released. Determine the location of an earthquake based on the timing of arrival of P and S waves at three seismic stations. Just know that the closer the P & S Waves are to each other the closer that station was to the earthquake. Predict how a change in the length of the fault that slips, the distance that the fault slips and the rigidity of the rock would affect the magnitude of an earthquake. Bigger slip=Bigger Quake Bigger distance=Bigger Quake More rigid=Bigger Quake Assess the earthquake risk for different regions based on their tectonic setting. To do this we examine the tectonic setting and history of earthquakes.
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