Deck 8: Landslides and Other Downslope Movements

Question 1

A steep slope will not collapse if the load is light.

Answer 1

False

Question 2

The frictional resistance depends on the ____.

A)slope angle only
B)load and area of contact only
C)load, slope angle, and area of contact
D)slope angle and load only
E)slope angle only

Answer 2

D

Question 3

A daylighted bed is ____.

A)an area of slippage due to subsurface ice exposed to sunlight
B)a fan-shaped spill of rock below a cliff edge
C)the bedrock uncovered during a translational slide
D)the area below an overhanging mass of snow
E)a gently sloped internal surface intersecting the lower slope

Answer 3

E

Question 4

Fresh snowfall tends to reduce the chance of an avalanche.

Question 5

Water pressure becomes an important factor in increasing landslide danger when ____.

A)slope surfaces become saturated
B)pressure increases with depth
C)pore spaces are filled with water
D)the water has significant clay content
E)the slope is composed of clays

Question 6

Rotational slumps are most common when slope material is strongly bonded together and lies on top of a linear slope.

Question 7

A slope will slide if the ____.

A)driving force is zero
B)resisting force is zero
C)driving force is greater than the resisting force
D)driving force is less than the resisting force
E)resisting force is equal to the driving force

Question 8

Water-rich sand or quick clay is likely to cause a ____.

A)deviational slide
B)divergent slide
C)rotational slump
D)lateral-spreading slide
E)translational slide

Question 9

Landslides can be caused by adding soil moisture.

Question 10

Hummocky landscapes and wavy roads are indications of landslides due to earthquakes only.

Question 11

In debris avalanches, the mass of material does not affect runout.

Question 12

Soil creep can be accelerated by freezing and thawing.

Question 13

The danger of quick clay is enhanced when the ____.

A)clay plates form triangular or tetrahedral structures
B)clay layer is frozen
C)clay grains align with slope angle
D)clay grains compact to take up less space
E)clay absorbs moisture

Question 14

The angle of repose of sand is ____.

A)lower for damp sand with small grain size
B)always higher for large grain size
C)always lower for large grain size
D)always higher for damp sand
E)always higher for dry sand

Question 15

Higher-mass rocks will have a shorter runout than smaller rocks.

Question 16

Water is a key factor in slope stability.

Question 17

The equilibrium of a slope is likely to be disturbed if the ____.

A)slope angle steepens or the load is either increased or decreased
B)slope angle is steepened or shallowed and the load is decreased
C)angle of repose is decreased
D)slope angle steepens or the load is increased
E)cohesion of grains is increased

Question 18

You would expect to find quick clays in ____.

A)the interior of a talus
B)old freshwater stream beds
C)exposed subsurface material from translational slumps
D)headscarps of rotational slumps
E)old marine beds or estuaries

Question 19

Thin films of water on sand grains ____.

A)can either increase or decrease cohesion depending on grain size
B)reduce cohesion and increase resisting forces
C)reduce cohesion and decrease resisting forces
D)increase cohesion and decrease resisting forces
E)increase cohesion and increase resisting forces

Question 20

Dams formed by rockfalls are a hazard that must always be removed before failure.

Question 21

The angle of _______________ is the steepest angle at which a slope will remain stable.

Question 22

Fluidization would be a hazard in a(n) ____.

A)snow avalanche
B)rockfall
C)rotational slump
D)lateral slump
E)debris flow

Question 23

Soil creep is most likely to result from ____ .

A)vibrational disruption of a slope
B)a desaturated soil with less cohesion
C)soil expansion and contraction
D)a higher angle of repose for the material than the slope angle
E)removal of mass at the head of the slope

Question 24

The greatest cause of death due to snow avalanches is ____.

A)frostbite
B)asphyxiation
C)blunt trauma
D)pressure
E)hypothermia

Question 25

The key element in creating avalanche danger is ____.

A)a frozen "cornice" or overhang
B)a frozen "cornice" or overhang
C)recent freezing or packing of the surface layer
D)a source of vibration
E)a weak layer in the snowpack

Question 26

In winter, Mount Rainier is ____.

A)at equal risk of landslides as compared to summer time
B)less at risk of landslides, as snow increases pressure on frozen water in rock fissures
C)less at risk of landslides, as snow lowers magma temperature
D)more at risk of landslides due to higher earthquake frequency
E)more at risk of catastrophic landslides due to the weight of snow and freezing water in rock fissures

Question 27

Which characteristic is NOT a factor when deciding to convert a natural landslide dam into a permanent dam?

A)geometry of the landslide dam
B)material of the landslide dam
C)rate of stream flow
D)ability to construct spillways and breaches
E)temperature of the water

Question 28

A(n) _______________ bed dips at a gentler angle than the hill it resides in.

Question 29

A large runout can be expected to extend a distance about ____ the height of the scarp.

A)equal to
B)a dozen times
C)twenty-five times
D)a hundred times
E)double

Question 30

A translational slide would be most likely in ____.

A)new snow on top of hoarfrost
B)large boulders embedded in sand
C)thick gravel over tuff
D)areas with deep, dry sand
E)thick, vegetated soil over bedrock

Question 31

The _______________ of a rockfall is the distance it will travel.

Question 32

The runout of a rockfall depends most heavily on ____.

A)pore size and cohesion
B)liquefaction and fluidization
C)mass and slope angle
D)slope angle and height of fall
E)mass and height of fall

Question 33

_______________ slopes form as fan-shaped piles of rock fragments against the base of a cliff.

Question 34

The most important factor in creating a translational slide hazard is ____.

A)a pre-existing weak surface parallel to a slope
B)ground motion and shaking
C)injection of water into the headscarp
D)removal of vegetation
E)collapse of a talus

Question 35

Which list is correctly ordered from the least rapid to the most rapid type of landslide?

A)debris flow, rockfall, rotational slump
B)debris flow, rotational slump, rockfall
C)rotational slump, debris flow, rockfall
D)rotational slump, rockfall, debris flow
E)rockfall, debris flow, rotational slump

Question 36

A rotational slide is most likely to occur in ____.

A)rounded sand grains on a gentle slope
B)large boulders with smooth sides
C)new snow lying above packed snow
D)homogenous, cohesive materials
E)slopes with high water pressure

Question 37

Removal of vegetation from a slope increases landslide danger because vegetation ____.

A)removes water from the soil
B)removes clays from the soil
C)holds the surface in a homogenous layer
D)concentrates water in the soil
E)amplifies the effect of shock and vibration

Question 38

_______________ slides move on preexisting weak surfaces roughly parallel to the slope.

Question 39

A rotational slump typically occurs in ____.

A)any material that lacks a planar surface guide
B)heterogeneous, cohesive material with a planar surface guide
C)heterogeneous, non-cohesive material with no planar surface guide
D)homogenous, cohesive material with a planar surface guide
E)homogenous, cohesive material with no planar surface guide

Question 40

A landscape hazard is best reduced when ____ of the slope.

A)mass is added at the head and water drained from the toe
B)mass is added at the head and water injected in the toe
C)mass is removed from the toe
D)water is removed at the head
E)mass is added at the toe and water drained from the toe

Question 41

You are hiking and come across a curious sight. To your left is a firm, rocky slope angled downward toward you. To your right are trees, which are pointed toward the slope at an angle. What would you conclude? What produced the effect?

Question 42

If air cannot escape spaces between rock fragments, _______________ may lubricate the flow.

Question 43

You are an avid skier. What factors should you be sensitive to when skiing to avoid avalanche hazards?

Question 44

Discuss the ways that water is able to increase and decrease the hazard of landslides.

Question 45

The vertical part of a slip surface is the _______________.

Question 46

Explain the cause and motion of a rotational slump.

Question 47

Soil _______________ is a slow downslope movement.

Question 48

_______________ is an important force holding soil grains together through static attraction, surface tension, or chemical bonds.

Question 49

The lowest end of a slip surface is the _______________.

Question 50

A road engineer is looking for ways to improve safety on a stretch of road bordered by a moderately steep field of small boulders. Suggest and describe three techniques that could be used practically.