Introduction to Environmental Geology, 5e (Keller)
Chapter 10 Slope Processes, Landslides, and Subsidence
10.1 Multiple-Choice Questions
1) A comprehensive term for any type of downslope movement of Earth materials is
A) subsidence
B) debris flow
C) avalanche
D) mass wasting
2) What strategy has been suggested to stabilize the La Conchita, California, landslide?
A) retaining wall construction
B) water drainage
C) planting of vegetation
D) slope grading
3) In Yosemite National Park, strong bedrock influences the formation of what types of
hillslopes?
A) convex upper slopes
B) concave lower slopes
C) free face and talus
D) glacial
4) How do slumps and translational slides differ?
A) translational slides are more damaging
B) slumps are more damaging
C) slumps are rotational, while translational slides are planar
D) slumps create debris flows, while translational slides do not
5) The safety factor for landslides is
A) the degree to which engineered structures have been installed to prevent landslides
B) the ratio of resisting to driving forces
C) the influence of changing climate on landslide hazards
D) the length of time that is likely to pass before a major landslide
6) Why are landslides more common on steep slopes?
A) Slope angle determines the relative magnitude of driving forces.
B) Water flows much faster on steep slopes.
C) The steeper the slope, the less vegetation plays a role in anchoring the slope.
D) Steeper slopes typically are underlain by weaker Earth materials.
7) Vegetation influences landslides in part by
A) anchoring the slope materials
B) influencing the local climate
C) aerating the soil
D) promoting deeper weathering of underlying rock
8) Why might the infiltration of water deep into a slide mass increase landslide hazards?
A) Deep infiltration forces vegetation to root more deeply.
B) Water will erode the subsurface materials, reducing strength of the slide mass.
C) Water in the deep subsurface influences soil formation, leading to shallow soil slips.
D) The water increases the pore water pressure, effectively lifting the slide mass from stable
ground beneath.
9) How did geology influence the Vaiont Dam disaster?
A) The geology in the adjacent hillslopes was dominated by weak rocks.
B) Porous rocks increased groundwater flow beneath the dam and weakened the structure.
C) The rocks created a steep slope on the canyon wall.
D) The geologic structure included steeply dipping faults.
10) How does road construction associated with timber harvesting contribute to landslide
hazards?
A) The roads add weight to the hillslope.
B) The roads loosen the soil, making shallow soil slips more likely.
C) Road construction removes large numbers of trees.
D) The roads alter the movement of surface water and groundwater.
11) What aspect of hillside development has contributed to the frequency of landslides in
southern California?
A) drainage of naturally occurring subsurface water
B) grading of hillslopes to create pads for home construction
C) logging of hillside vegetation
D) addition of weight to slide masses
12) On what information is a landslide hazard map based?
A) geology and inventory of past landslides
B) subsurface water flow
C) climate
D) grading codes for home construction
13) Why is drainage control sometimes an effective method of landslide control?
A) it reduces the amount of water in the hillslope materials
B) it reduces the growth of vegetation
C) it reduces the thickness of the slide mass
D) it reduces the permeability of the rocks
14) How might the 1983 Thistle landslide have been prevented?
A) removal of the vegetation that added mass to the hillslope
B) rerouting of the highway that crossed the slide mass
C) construction of retaining walls at the foot of the slope
D) examination of landslide history and installation of drains
15) Why does withdrawal of fluids sometimes lead to subsidence?
A) The smaller amount of water leads to greater chemical weathering.
B) The water holds subsurface caverns open.
C) The fluid pressure provides partial support for the overlying rock mass.
D) The water adds weight to the mass of Earth materials.
10.2 True/False Questions
1) Hillslopes typically are static systems.
2) Hillslopes in weaker rocks tend to be more gently sloped.
3) Slumps and debris flows tend to occur separately in time and space.
4) A safety factor of 1 implies that driving forces are 10 times greater than resisting forces.
5) Debris avalanches tend to occur on steep slopes.
6) Climate influences landslides by determining the vegetation present on a slope.
7) Erosion of the base of a slope may increase landslide hazards.
8) Grading of slopes can either increase or decrease landslide hazards.
9) The expense of preventing landslides is usually too great for the prevention strategies to be
feasible.
10) Sinkholes often result from water table fluctuations.
11) Land subsidence in the Central Valley, California, results mostly from oil extraction.
12) The Vaiont Dam disaster occurred when landslides caused the dam to fail.
13) Logging operations always increase landslide hazards.
14) The cost of completely stabilizing the La Conchita, California, landslide is far less than the
10.3 Short Answer Questions
1) All slope movements fall under the term ________.
2) ________ is the downslope movement of a coherent block of Earth material.
3) The lower portion of a slump typically evolves into a(n) ________.
4) The ratio of resisting to driving forces is called the ________.
5) The noncohesive downslope movement of saturated Earth materials is called a(n) ________.
6) The spontaneous liquefaction of clay-rich sediment is called ________.
7) The Thistle landslide, in the state of ________, was one of the most expensive landslides in
U.S. history.
8) One of the most effective methods of stopping an active slide is ________.
9) Snow avalanches tend to move down tracks called ________.
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10) ________ are caused by the collapse of caverns.
11) ________ are designed to provide mechanical support at the base of a slope.
12) ________ and ________ can severely increase landslide hazards in mountainous terrains.
13) The ________ disaster in Italy was caused by landslides entering the lake