Name Learning Unit 9 Mass Wasting and Subsidence Review Questions This assignment is designed to assess your understanding of Unit 9 and includes some of the Questions for Review at the end of Chapters 8 and 9 from your text plus a few additional questions Each question can be answered in one to two sentences Please limit yourself to a maximum of three sentences Access the assignment complete it with ANSWERS IN A DIFFERENT COLOR FONT as a separate file and send it back for evaluation and grading through the assignment tab by or before the due date 1 What parts of the United States are most susceptible to landslides Western California and Oregon or Coast Ranges of western Colorado Appalachians or western Carolinas and Virginia West Virginia Pennsylvania 2 Why do people build in landslide prone areas For the views it is in a scenic area boulders make for scenic landscaping 3 Why is the friction force on a gently sloping slip surface greater than that on a steeply sloping slip surface A larger proportion of the load is pressing against the slip surface on a gentle slope 4 What is cohesion as applied to a slope The holding together of otherwise loose grains on a slope generally by moisture or cement 5 What would permit sand grains to stand at a steeper slope What would make a pile of sand grains collapse to be almost flat A little moisture permits sand grains to stand at a steeper slope like building a sand castle Too much water enough to fill all of the pore spaces between the grains would make a pile of sand grains collapse too much water destroys a sand castle 6 What can you use to recognize the action of soil creep Tree trunks that bend out from a slope before curving up fences or walls that tilt down slope cracks in walls and foundations sticking doors and windows 7 What types of surfaces are most prone to sliding What is the difference between a slump and a translational slide Bedding planes between layers of sedimentary rock dipping towards an open space Slopes undercut by erosion at their base Old landslides slip surfaces A slump fails as a relatively coherent rotational mass whereas a translational slide moves parallel to the surface of the slope 8 List the main factors that affect whether a slope will fail driving forces of mass wasting Increase in slope steepness shear force of gravity Reduction of slope strength by weathering by burrowing animals or by infiltration of water Water saturation The single most important factor in most mass wasting Water saturation can result from heavy rain rapid snowmelt leaking water or sewage lines or poor drainage Water saturation weakens rock by building up pore pressure and by lubricating contacts between particles Increase in weight at top of a slope Removal of support at the base of a slope Shaking by either natural processes earthquakes or human activities explosions heavy traffic 9 List three ways in which human activity can increase the danger of mass wasting Adding water loading the top of a slope undercutting the slope removing vegetation 10 List several distinctly different ways in which water can be removed from a wet slope that has slide potential Water within the ground can be controlled by hydrauger holes horizontal holes drilled into the ground and lined with perforated pipe Excess water leaks into the pipes and flows into other pipes that take it away from the slope An example is shown in this photograph Control of surface water flow on vulnerable slopes can be done by planting vegetation increase evapotranspiration and or by drainage ditches set at regular intervals on the slope to permit external drainage 11 What three methods can be used to minimize damage from rockfalls rockbolts coating with shotcrete draping with heavy wire mesh 12 What can be done to stabilize a steep high dangerous rock cliff or roadcut to keep it from collapsing onto a highway or railroad track See question 11 13 The disastrous Vaiont landslide in Italy involved what combination of circumstances Case in Point A Coherent Translational Slide Triggered by Filling a Reservoir Weak rock layers of limestone see question 14 dipping parallel to a slope filling a new reservoir at the base of the slope and prolonged heavy rainfall 14 What causes caverns in limestone that is where does the limestone go and why Rainwater dissolves carbon dioxide to make weak carbonic acid That acid seeps down into cracks in the limestone dissolving it Most of the limestone dissolves near the top of the water table where there is greater flow of groundwater along bedding surfaces The groundwater carries away the dissolved limestone 15 What is in water in the ground that helps it dissolve limestone Where does that substance come from Carbonic acid it forms from carbon dioxide in the air combining with rainwater 16 What causes sinkhole collapse that is where is the cavity that it collapses into and how does that cavity form Soil above a limestone cavern percolates or travels down into the cavern leaving a soil cavity above When the soil cavity gets large enough it may collapse to form a sinkhole 17 What types of human behavior typically lead to widespread ground subsidence Mining groundwater or petroleum 18 Name three of the eight states with the largest areas of ground subsidence including sinkholes Florida Georgia Texas New Mexico Kentucky Tennessee Virginia Missouri 19 What is karst and how does it form How would you recognize a karst landscape Karst is the ragged surface dissolved on the surface of limestone bedrock formerly buried under soil Rainwater dissolves carbon dioxide to make weak carbonic acid That acid seeps down into cracks in limestone dissolving it and leaving high points or spines between the cracks 20 Venice Italy is noted for numerous canals instead of normal streets that cars drive on Why doesn t it have many normal streets Explain briefly and to the point Case in Poing Subsidence Due to Groundwater Extraction Extraction of groundwater under the city caused subsidence and sinking of the city below sea level
View Full Document
Unlocking...