Deck 10: Slope Processes, Landslides, and Subsidence

Question 1

A safety factor of 1 implies that driving forces are 10 times greater than resisting forces.

Answer 1

False

Question 2

Hillslopes in weaker rocks tend to be more gently sloped.

Answer 2

True

Question 3

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

Answer 3

A

Question 4

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

Question 5

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.

Question 6

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

Question 7

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

Question 8

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

Question 9

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

Question 10

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.

Question 11

A comprehensive term for any type of downslope movement of Earth materials is

A)subsidence
B)debris flow
C)avalanche
D)mass wasting

Question 12

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

Question 13

Debris avalanches tend to occur on steep slopes.

Question 14

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

Question 15

Slumps and debris flows tend to occur separately in time and space.

Question 16

Hillslopes typically are static systems.

Question 17

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.

Question 18

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

Question 19

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.

Question 20

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.

Question 21

________ are designed to provide mechanical support at the base of a slope.

Question 22

The cost of completely stabilizing the La Conchita, California, landslide is far less than the cost of relocating residents to more stable ground.

Question 23

Snow avalanches tend to move down tracks called ________.

Question 24

The noncohesive downslope movement of saturated Earth materials is called a(n) ________.

Question 25

Sinkholes often result from water table fluctuations.

Question 26

The ratio of resisting to driving forces is called the ________.

Question 27

________ are caused by the collapse of caverns.

Question 28

Climate influences landslides by determining the vegetation present on a slope.

Question 29

One of the most effective methods of stopping an active slide is ________.

Question 30

________ is the downslope movement of a coherent block of Earth material.

Question 31

The expense of preventing landslides is usually too great for the prevention strategies to be feasible.

Question 32

All slope movements fall under the term ________.

Question 33

Grading of slopes can either increase or decrease landslide hazards.

Question 34

Land subsidence in the Central Valley, California, results mostly from oil extraction.

Question 35

The Vaiont Dam disaster occurred when landslides caused the dam to fail.

Question 36

Logging operations always increase landslide hazards.

Question 37

The lower portion of a slump typically evolves into a(n) ________.

Question 38

Erosion of the base of a slope may increase landslide hazards.

Question 39

The spontaneous liquefaction of clay-rich sediment is called ________.

Question 40

The Thistle landslide, in the state of ________, was one of the most expensive landslides in U.S. history.

Question 41

The ________ disaster in Italy was caused by landslides entering the lake

Question 42

________ and ________ can severely increase landslide hazards in mountainous terrains.