GEOL 101 Test 3 Study Guide
GEOL 101 Test 3 Study Guide GEOL 101
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This 12 page Study Guide was uploaded by Victoria Williams on Tuesday April 5, 2016. The Study Guide belongs to GEOL 101 at George Mason University taught by Mark Uhen in Fall 2016. Since its upload, it has received 142 views. For similar materials see Introductory Geology in Geology at George Mason University.
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Date Created: 04/05/16
Study Guide 1 Test 3 Study Guide Crustal Deformation – This section uses a lot of vocabulary! Try to write out the definitions. India has been in an ongoing collision with Asia Major for millions of years, what is the geographical result of this collision? Deformation is a term applied to changes in size, shape, orientation, and position of a rock mass. Commonly seen with plate tectonics. Factors of deformation, write out the definition of each and what they do to rocks. o Stress o Compression o Tension o Shear How rocks perform under stress o ___________ Rock will snap under compression, fractures and pulls apart with tension, and breaks up and slides with shear stress. o ___________ Rock will bend in waves, stretch thinner, and the rock might move in two directions, but not break apart. _______ is researched in structural geology to describe the change in the shape of a rock body due to stress. General Behavior of rocks o What happens to a rock that is put under stress slowly without surpassing its elastic limit? If the stress is removed, what will the rock look like? o What happens to a rock put under stress that is surpassing its elastic limit? If the stress is removed, what will the rock then look like? Temperature and Pressure o Low Temperature and Low Pressure ________ deformation o High Temperature and High Pressure ________ deformation o Low Pressure, Low Heat, but high stress causes the rock to _______. This normally happens at the surface of the earth. Mapping Geologic Structures o _______ is the compass direction of the line produced by intersecting a layer with a horizontal surface o _______ is the inclination of the surface perpendicular to the previous mapping method. Folds Study Guide 2 o Images in lecture are similar to: o o ________ Folds appear to be the same on both sides of the center line (also referred to as the ______ plane). The dip angles are the same. When there is a higher slope in the middle, it is called a(n) ____cline. o There are similar structures called plunging ____clines where the ridges are not perpendicular but they meet in a ‘clothes iron’ shape. A new factor arises for mapping this geological structure, plunge line. Anticline and Synclines o Ridges are composed of ________ and the dips between the ridges are ________. These inclines can be at different angles and can be asymmetrical o ______clines are rare structures where a fault occurs in layers of rock that crack deeper down into the earth but the rock layers above are ductile and create a ‘bump.’ Domes and Basins o Domes expose the _______ strata in their centers. o Basin expose the _______ strata in their centers. o Using the image, identify which structure is a dome and which is a basin. (Hint, look at the curve in the rock layers). And explain how they became to look like the images. DipSlip Faults exhibit motion up or down along a dip. In a normal fault, the (foot/hanging) wall falls, circle one. In a reverse slip, the (foot/hanging)wall rises (same term). Thrust faults are similar to reverse but they occur with a low angle slip. o In the image, identify which slab is the Footwall and which is the Hanging Wall. Fault Scarps are visible parts of the slip on the surface seen in a normal fault. Study Guide 3 Normal faulting is associated with tensional stress, the _____wall goes up and creates higher elevations. Horsts and Grabens are rather difficult to explain. ______ are the elevated parts of the fault and the _______ are what ‘fall’ down and make a valley. This happens when the land is being pulled apart. Half_______ only fall on one side. See the image for help. StrikeSlip faults exhibit motion along a strike (a trend along the surface of the earth in which _______ has occurred). What usually forms as a result of this? (hint: grinding) Transform Faults are a type of strikeslip fault but are special because they separate two tectonic plates. They are not in a straight line, they are in pieces offset from one another. What is an example of an exceptionally large one? Joints are fractures in which no _________ has occurred. They are made with igneous rocks that cool in cracked columns. Mass Wasting Where was the largest land slide ever recorded? Define Mass Wasting and the role gravity plays in it. What great American landmark is a result of mass wasting over time? It has experienced flooding that causes landslides, the waste is swept away by the floodwater. Controls of Mass Wasting o If the soil is dry with high friction, will mass wasting occur? Study Guide 4 o What about saturated soil with less friction? Explain why one allows mass wasting and the other does not. Angle of Repose is the angle at which unconsolidated particles gather in a pile. These angles are normally between 25 and 40 degrees, what influences the angle in which the particles come to a rest? What does vegetation do to help prevent mass wasting events? What if all vegetation in an area was suddenly removed, what is more likely to happen to this area? How can earthquakes cause mass wasting events? Description of Mass Wasting o Material – Where do mass wasting events with these materials normally occur? What can set them off? Rock Mud Ice o Motion – Describe the movement of a slide if it goes through any of these motions. Fall Slide Flow o Rate of Motion – Explain what makes a mass wasting event go a certain speed. Slow Fast Other types of Mass Wasting Events o Slumps – Caused by clay and its tendency to fracture circularly. How does the earth move? What shape is the crack it slides on? o Rockslides – Occur when layers of rocks break apart on a planar surface. Where was there a large one of these in the U.S. that was extremely devastating? o Avalanche – Just like other mass wasting events, except it’s made out of ice and snow. o Debris Flow – Made up of poorly sorted rock and soil in water that acts like a liquid. What happens when the flow begins to slow down? o Lahar – Flow of volcanic ash and water, tend to be boiling hot. What state in the US experiences these on a regular basis? Why? o Earthflows – Similar to a slump, but they don’t move on a curve. It moves downhill in a ‘tongue’ shape mass. o Creep – Slow, downslope movement caused by expansion and contraction cycles in the soil. What causes these cycles? See the image below Study Guide 5 o Permafrost – Permanently frozen ground. What is currently happening to our planet’s permafrost? Why is this happening? Solifluction only happens where there is permafrost, saturated soil moves slowly downslope in lobes. Why does this happen? Why doesn’t the permafrost move too? Running Water How much of earth’s water is drinkable fresh water? Hydrologic Cycle – Explain what happens to water at each stage o Evaporation o Condensation o Precipitation o What is one way that water is removed from this cycle? Water soaking into the ground from meteoric water (rain) is called Infiltration. Number the order of the zones water passes through o Capillary Fringes o Water Table o Soil Zone o Saturated Zone What is runoff? Why does it happen? Define the following terms to help you understand. o Infiltration Capacity (what effects soil’s capacity for taking in water?) o Sheet flow o Rills Streams and Rivers form due to runoff, rills collect into streams and rivers (geologists use this term interchangeably) What is a Drainage Basin? What is one of the largest Drainage Basins in the US? What about a Drainage Basin near us in Virginia? River Systems flow in channels and the water can flow in two ways, describe each. o Laminar Study Guide 6 o Turbulent Channel Shape and Flow Velocity o Where does water move the fastest? Why? o Where does water move the slowest? Why? o Which moves faster: Shallow and wide river, or a deep and narrow river? What is discharge? D (m /s) = Cross Sectional Area (m) x Velocity (m/s) is its formula. What does this help tell us? o Crosssectional area = Width x Height o Which river has the most discharge, and why? Define what the Stream Gradient is. It has the formula: Average Gradient = Highest point on river / Distance the river runs Sediment Transport – Define the size of the particles in each load, and what speed they are most likely going at due to this size. o Dissolved Load o Suspended Load o Bed Load Moves through rolling, sliding, and saltation/bouncing Stream Erosion – Streams holding sediment weather rocks faster. There are two main ways that these streams erode material, describe how each happen. o Abrasion o Potholes Capacity and Competence are factors in how much a stream can carry. Define each. o Capacity o Competence The size and speed of a stream influences its capacity and competence, determine the capacity and competence for these examples: Study Guide 7 Large stream, slow flow Small stream, slow flow Large stream, fast flow Small stream, fast flow Sediment Deposition – Streams form in a meandering/winding way. Use the image and determine where the faster flow is and where the slower flow is. Think of capacity and competence. What fraction of the Colorado River will reach the gulf? Stream Channels – Bedrock vs. Alluvial Channels. Which channel is more freely flowing? Which one has a very strict course, like in the Grand Canyon? o Alluvial channels are known to have many formations, describe these two and where they are more likely to be found (in gradient and elevation) Braided Meandering Meander Cutoff – Using the image, describe what is happening to create the new oxbow lake. What is the base level for most streams and lakes? Base level is the lowest a body of water can erode, logically. In rare cases a body of water can sink below the base level, an example if this is the Dead Sea. Define each term and explain how, why, and where they happen: o Valley Deepening o Valley Widening o Floodplains o Stream Terraces o Incised meanders o Deltas o Natural Levees o Alluvial Fans Study Guide 8 Drainage Patterns – Geomorphology (the change in the earth). Describe the shape of each pattern listed below and where they happen. o Dendritic o Radial o Rectangular o Trellis Why do Water Gaps form? Hint: They occur in areas with synclines and anticlines. Describe what happens when Stream Piracy occurs, they are related to Water Gaps Floods occur with an excess of water in areas where the soil is already saturated to capacity or it is unable to absorb water at all. Every flood is devastating nowadays, and the following are three common types. When do most of these happen? Which are most destructive (in terms of human lives and property lost). Hint: most destructive events happen suddenly. o Regional Floods o Flash Floods o Dam Failure Floods Ground Water What percentage of fresh water in the US comes from groundwater? How much of earth’s fresh water is in ground water? Hint: not very much. Basic Definition of Groundwater: Water under the surface of the ground filling up pore spaces between soil/rock. The top soil is unsaturated with air between the particles, as you go deeper down the soil becomes filled with more and more water. The space where the soil is completely saturated is called the Water Table, which is recharged with rain and snowmelt. Groundwater and Streams – What relationship does the water table have with each of the following streams? Level of the stream is important. o Gaining Stream o Losing Stream o Connected Stream o Disconnected Stream What is porosity? How does it affect how much water can be absorbed by the soil? Permeability is the ability for sediment or rock to transmit fluid, measured by Hydraulic Conductivity. Define these two important terms: Study Guide 9 o Specific Yield o Specific Tension o Use this image to help Aquifers and Aquitards – define each term and how it interacts with water. o Aquifer o Aquitard Groundwater Movement – best thought as a compromise between gravity and differential pressure, which is what makes water move towards area of low pressure. Hydraulic Gradient is the velocity of groundwater flow, which is proportional to the slope of the water table. The height of humanmade water wells (how deep they run) and the distance they are apart are important. The formula is defined as: o H1 = height of water table at well 1 o H2 = height of water table at well 2 o D = straight line distance between wells 1 and 2 o HG = (H1 – H2)/D Darcy’s Law o K = Coefficient of hydraulic conductivity o A = Aquifer cross sectional area (length x width) o Discharge (Q) = KA*(h1h2)/D Where and how do Natural Springs form? Think about their relationship with aquitards and water flow. Where are Hot Springs and Geysers formed? Hint: It’s below the water table with high heat Humans tap water out of the Water Table a lot, and where a lot of water has been taken the water table dips down in that area. What is this dip called? Define what an Artesian Well is. Hint: It’s like an aquifer/aquitard sandwich with differentiating elevations. In places of drought, what happens to the water table? If enough water (or oil or gas) is removed in an area, the ground will sink. What is this called? How far has the earth dropped in San Joaquin Valley, California? There are two common ways groundwater can be contaminated, explain each o Saltwater Contamination o Groundwater Contamination (hint: human activity) Study Guide 10 2+ Caverns H2O + CO 2 H C2 (3arbonic Acid), CaCO + H3CO 2Ca 3+ 2 HCO 3 o Caves are most commonly made out of Limestone (Calcium Carbonate) that has been eroded by water. o Define the following structures in caves, how they are formed, where they form, and what they look like. Stalactites Stalagmites What happens when a cave erodes away so much the roof collapses in? These happen a lot in Florida. Karst Topography is a result of these collapsed caves, streams disappear into them and into a grand underground cave system. Then over hundreds of years water erodes the limestone, leaving pillars of insoluble rock called Karst Towers. The surface of the earth here used to be the bottom of a cave. Wind and Deserts How much of earth’s land mass is desert? Deserts have very low precipitation and receive less water because of evapotranspiration (evaporation, water evaporating; transpiration, water lost from plants to the air). Explain why this decreases the water level in deserts. What is the area surrounding most deserts that are filled with scrubby, dry grass? LowLatitude Deserts o Most deserts are formed along the Tropics of Capricorn and Cancer, or the Subtropics. o Look at the image, the blue and purple signify cold air sinking down. The green shows the place where the cold air mixes with the warm air that is rising from the equator. The orange areas are slightly cooled and tend to create rain. The yellow areas lack the water the orange get, and thus deserts form here. Middle Latitude Deserts o Also known as Rain Shadow deserts o These deserts form in places where wind is coming over the ocean, laden with water, that rain onto plains and a mountain Study Guide 11 range, aka the Windward side. All the water is depleted by the time the air moves over the peaks and falls on the other side, leaving the Leeward side a dry desert. Dry vs. Humid o Higher temp = more evaporation o Lower temp = less evaporation o Which of these climates become deserts a lot easier? Desert Precipitation o Precipitation usually occurs in one shot seasonally. o A specific type of stream carries water only during these rainy seasons. What are they called and where do they usually form? Evolution of Desert Features – Define each term below as they pertain to mountainous desert areas. o Horsts o Grabens o Playa Lakes o Alluvial Fans o Bajadas o Inselberg (ex. Uluru in Australia) Wind Transport of Sediment – Extremely similar to water transport. o Which can carry more particles, water or air? Why? o Particle loads, Suspended loads, and Saltation/Bouncing/Creeping all happens in wind transportation just like in water. o What is Aeolian Sedimentation? How can geologists use this to map out ancient wind patterns? Desertification – the process of more deserts being formed due to evapotranspiration and human activity. What do humans do to increase the pace at which this is happening? (hint: animals) Blowouts occur when the wind blows away sand from around a desert plant, who have deep roots, leaving a kind of plant ‘pillar.’ Why do these plants need such deep roots? Desert Pavement – Using the diagram, describe how this occurs (deflation = wind) Ventifacts are polished, angular rocks. What causes the angles? Study Guide 12 Sand Dunes are mounds or ridges of winddeposited sand particles. Cross beds develop in sand dunes, giving them an asymmetrical shape. Wind can also shape sand and rock like water can into rills. Dunes climb up at a gentle slope before dropping off suddenly. What is this drop called? The following factors influence the shapes of sand dunes: o Wind Direction o Wind Strength o Local Topography o Particle Size There are many types of dunes, using the image try to identify each. Word Bank: Transversal Dunes, Barchan Transversal Dunes, Barchan Dunes, Star Dunes, Parabolic Dunes.
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