GLY1000 Odom Test 3 Study Guide Just a heads up Professor Odom hinted that around 75 of the test will consist of questions involving the following topics Throughout this study guide these topics will be marked with an to indicate their importance Make sure you take extra time to study the following 17 topics Relative rates of different types of mass wasting processes Velocity of ground water Characteristics of streams at different stages of stream evolution Factors influencing runoff infiltration Factors influencing the rate of recovery of a depressed aquifer i e one that has been drawn down or had the water table lowered Factors influencing the stability of slopes An aquifer vs aquiclude Sinkholes How dams cutoffs levees and other things might affect a stream Things that might help control slumping and things that can cause slumping How a cone of depression forms and how the water table can recover Levees How rivers increase their lengths Factors affecting stream velocity competency and capacity The effects of forest land urbanization on mass wasting streams and groundwater Graded streams Groundwater problems that can occur Mass Wasting Mass Wasting the down slope hill movement of rock soil or sediment under the influence of gravity Mass wasting events occurs in different ways and at different rates depending on the types of materials involved such as rock soil or earth mud debris and the motion involved fall slide flow Factors that affect mass wasting and the stability of a slope 1 Types of materials involved rocks sediments soils etc a Unconsolidated loose soils or sediment are more prone to mass wasting than are consolidated tightly packed rocks 2 The steepness of the slope 3 Amount of water present a Low amounts increased stability b High amounts decreased stability 4 Vegetation in the area 1 a The roots of vegetation can sometimes have an anchoring effect on the stability of slopes 5 Height of the slope 6 Climate such as freeze thaw cycles a Freeze thaw cycles Water seeps into the pours of a rock and when it freezes the water expands This expansion increases the strain on the rock and causes the rock to become weaker As the climate becomes warmer the ice melts and the water is released from the rock Repeated cycles of this process weaken the rock so much that it breaks into small fragments that are carried downhill by gravity 7 The presence and orientation of planes of weakness a Joints a brittle fracture surface in rocks along which little or no displacement has occurred b Bedding a layer of sediment or volcanic material that is distinctly separate from other layers Inconsistencies can cause weakness c Foliations the result of pressure and recrystallization when rocks undergo metamorphosis It is the layering and parallel alignment of flattened or directionally oriented mineral crystals Slate phyllite schist and gneiss are all metamorphic rocks with foliated texture 8 Human Activities such as a Surface Mining b Construction c Pumping oil water etc d Irrigation projects e Hillside excavation Natural processes that over steepen slopes 1 Stream erosion continued water flow causing rocks to be eroded and the deepening of a V shaped valley 2 Wave erosion waves in oceans and other large bodies of water produce coastal erosion The pure energy of waves along with the chemical content of the water is what erodes the rock of the coastline 3 Tectonic uplift a geological process most often caused by tectonic plate movement which increases the elevation of an area 4 Volcanic activity The Different Types and Rates of Mass Wasting 1 Creep Downhill creep is a long term process often at a cm year or less The combination of small movements of soil or rock in different directions over time This process is directed by gravity in a gradual downhill direction The steeper the slope the 2 faster the creep Creep can be facilitated by freeze thaw cycles or biological agents such as worms or rodents that move the soil grains around 2 Slump A slipping of coherent rock material along the curved surface of a decline Slumps involve a mass of soil or other material sliding along a curved surface shaped like a spoon The speed of slumps varies widely ranging from meters per second to meters per year The structure and geometry of a slump can be seen below 3 Avalanche A mass of material moving rapidly down a slope An avalanche is typically triggered when material on a slope breaks loose from its surroundings this materials quickly collects and carries additional material down the slope Types of avalanches include rock avalanches ice avalanches and debris avalanches Landslides a general term that applies to all slides flows and falls that occur at a fast or moderately fast rate Common Evidence of Past Mass Wasting Events Bent trees Offsets in roads or fences Tilted telephone or utility poles Ways to Prevent Mass Wasting Events in the Future Steep slopes can be covered or sprayed with concrete covered or with a wire mesh to prevent rock falls Retaining walls could be built to stabilize a slope If the slope is made of highly fractured rock rock bolts may be emplaced to hold the slope together and prevent failure Drainage pipes could be inserted into the slope to more easily allow water to get out and avoid increases in fluid pressure the possibility of liquefaction or increased weight due to the addition of water Over steepened slopes could be graded to reduce the slope to the natural angle of repose 3 In mountain valleys subject to mudflows plans could be made to rapidly lower levels of water in human made reservoirs to catch and trap the mudflows Trees or other vegetation could be planted on bare slopes to help hold soil Streams What Happens to Water That Does Not Evaporate 2 Possibilities 1 Infiltrates the ground groundwater a Factors that affect the infiltration capacity of the ground the permeability and porosity of the surface material the slope of the land i ii iii amount and type of vegetation iv recent amounts of precipitation the saturation of the land 2 Runs off the surface sheet flow or stream flow a Sheet Flow An overland flow or downslope movement of water taking the form of a thin continuous film over relatively smooth soil or rock surfaces and not concentrated into channels such as during flooding b Stream Flow The flow of water in streams rivers and other channels Natural and Human Activities That Increase the Flooding Potential of Streams Deforestation causes flooding because of erosion from
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