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 In the United States the most severe in states with hilly or mountainous terrain which are mainly in the mid west west and eastern regions of the United States 2 Why do people build in landslide prone areas People try to build in landslide prone areas because they think that if they build preventatives then they will not be effected by landslides There are building codes that limit the steepness of slopes and the types of fill used in construction 3 Why is the friction force on a gently sloping slip surface greater than that on a steeply sloping slip surface The reason for the friction force being greater on a gently sloping surface is because a bigger amount of the landslide is pressing against the slip surface while moving down the gentle slope 4 What is cohesion as applied to a slope Cohesion is an example of Forces that resist movement down the slope are grouped under the term shear strength 5 What would permit sand grains to stand at a steeper slope would make a pile of sand grains collapse to be almost flat What In order for the sand grains to stand at a steeper slope the stability of the soil or land would have to have been compromised after the last landslide In order for the sand grains to fall flat the land would have needed to suddenly settle in something such as a sinkhole 6 What can you use to recognize the action of soil creep A person can look at bent trees tilted fences poles cracks in walls doors and windows stick 7 What types of surfaces are most prone to sliding What is the difference between a slump and a translational slide Steep surfaces are most prone to sliding Surfaces that have loose or weak rocks or soil are also more prone to having slides Slumps happen along a curving concave up surface of failure often spoon like in shape while transitional slides happen most often on a relatively flat sloping surface of failure 8 List the main factors that affect whether a slope will fail driving forces of mass wasting The main factors that affect whether a slope will fail are an 1 increase in the slope s steepness 2 a reduction of slope strength usually because of weathering burrowing animals or infiltration of water 3 Water saturation when heavy rain rapid snowmelt leaking water or sewage lines or poor drainage happens in a short time 4 an increase in weight at top of a slope 5 the removal of support at the base of a slope and 6 shaking by either natural processes such as an earthquake or by human cause such as an explosion or heavy traffic 9 List three ways in which human activity can increase the danger of mass wasting Humans can increase the risks of mass wasting by overbuilding and depleting the nutrients in the land and causing the soil to become unstable conducting explosions or it can be caused by heavy traffic 10 List several distinctly different ways in which water can be removed from a wet slope that has slide potential Some possible ways that water can be removed from a wet slope are by planting trees or other kinds of vegetation drainage ditches can be set up to run down the slope the water can be drained out hydrauger holes can be drilled into the ground and then lined with perforated pipe so the excess water can then leak out 11 What three methods can be used to minimize damage from rockfalls 1 Rock bolts used to reinforce slopes consisting of cracked and fractured rock can be inserted 2 a deflection wall can be built to divert and funnel debris flows around structures and 3 a Shotcrete a layer of concrete is sprayed out of a pressurized gun to cover a slope can be built 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 Inserting rock bolts are a great way to stabilize steep cliffs and protect the roads and highways underneath from falling debris The bolt is a retaining device used to reinforce slopes consisting of cracked and fractured rock They can be used to reinforce cliffs overhangs and tunnels Bolts that are anchored in concrete are particularly strong 13 The disastrous Vaiont landslide in Italy involved what combination of circumstances Case in Point A Coherent Translational Slide Triggered by Filling a Reservoir The two most common circumstances are when the land starts dipping in planes of weakness toward an open space These planes might be sedimentary bedding planes faults or fractures in the rock 14 What causes caverns in limestone that is where does the limestone go and why The cavers in limestone is caused by groundwater which is slightly acidic the caverns are called karst terrain 15 What is in water in the ground that helps it dissolve limestone Where does that substance come from The water in the ground contains acid which is what helps to dissolve the limestone That acid comes from rocks and other sediments in the earth 16 What causes sinkhole collapse that is where is the cavity that it collapses into and how does that cavity form Sinkholes are caused by acidic groundwater The cavity is directly underneath and the surface The acidic water sinks down forming cavers and then the caverns collapse and form the sinkholes 17 What types of human behavior typically lead to widespread ground subsidence The most severe in the United States happen in agricultural areas with intensive groundwater pumping 18 Name three of the eight states with the largest areas of ground subsidence including sinkholes Three of the states with the largest areas of ground subsidence are Nebraska Illinois and Florida 19 What is karst and how does it form How would you recognize a karst landscape Land that has been completely perforated with sinkholes has the rugged and otherworldly appearance 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
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