Deck 12: Mass Wasting: the Work of Gravity

Question 1

Why was the Alaskan pipeline built above ground and insulated?

A)to protect against damage from roots of large trees uprooted in windstorms
B)to keep the crude oil cool and highly fluid
C)to protect against damage from herds of elk and deer
D)to protect the pipeline against damage due to thawing ground and to keep the crude oil hot and fluid

Answer 1

D

Question 2

Which mass wasting process has the slowest rate of movement?

A)creep
B)solifluction
C)rock avalanche
D)slump

Answer 2

A

Question 3

Consider a steep highway cut made by removing slightly weathered to fresh, fractured, granite bedrock. Which of the following situations is most stable against rockslides?

A)two sets of fractures, one inclined toward the road cut and the other away
B)two sets of fractures, one widely spaced and sub- horizontal, the other inclined away from the highway cut
C)one set of widely spaced fractures inclined towards the road cut
D)one set of widely spaced, sub- horizontal fractures

Answer 3

D

Question 4

Which of the following statements concerning mudflows is NOT true?

A)In hilly areas, mudflows move down the canyons and stream valleys.
B)Mudflows may be caused by heavy rains or melting snow.
C)Mudflows deposit talus slopes.
D)Mudflows can move and carry very large boulders and other coarse debris.

Question 5

All of the following are factors affecting mass wasting EXCEPT for _ .

A)geologic age
B)water
C)slope angle
D)gravity

Question 6

All of the following are possible indicators that creep is occurring EXCEPT for .

A)curved tree trunks
B)cracks in roads or sidewalks
C)tilted fences or power line poles
D)an extremely thick soil profile

Question 7

Which of the following mass movements is most likely to occur in a geologic setting where the rock strata are inclined?

A)debris flow
B)rockslide
C)slump
D)creep

Question 8

During wet weather or times when snow is melting, sometimes the downhill toe of a slump .

A)becomes an earthflow
B)turns into a rock avalanche
C)stops moving because water makes the clay sticky
D)collapses and is deposited as talus at the base of the slope

Question 9

Which one of the following operates primarily in areas of permafrost?

A)soil creep
B)mudflow
C)solifluction
D)rock avalanche

Question 10

Which of the following locations was affected by mudflows triggered by an earthquake in 2001?

A)Oslo, Norway
B)Buffalo, New York
C)Johannesburg, South Africa
D)Santa Tecia, El Salvador

Question 11

How do freezing, thawing, wetting, and drying contribute to soil creep?

A)Gravity exerts a much stronger force when the soil is wet and thawed.
B)The soil expands and contracts, lifting particles and dropping them a slight distance downslope.
C)Eventually, these cause the soil and regolith to suddenly slide down the slope.
D)The soil becomes much weaker when dry and frozen.

Question 12

A geologist wants to locate a horizontal coal bed on a soil- covered slope where soil creep is active. A distinctive sandstone bed underlies the coal bed. On the basis of weathered sandstone fragments in the soil, where is the coal bed?

A)just below the lowest piece of sandstone seen in the soil
B)just above the highest piece of sandstone seen in the soil
C)just above the lowest piece of sandstone seen in the soil
D)just below the highest piece of sandstone seen in the soil

Question 13

Consider a weathered rock or soil particle lying on a slope. How will the gravitational force pulling the particle downward along the land surface vary with the inclination of the slope?

A)It will possibly increase or decrease as slope angle is lessened, depending upon other factors.
B)It is not affected by the slope angle.
C)It will decrease as the slope angle is lessened.
D)It will increase as the slope angle is lessened.

Question 14

Which statement best describes slumping, a mass wasting process?

A)A mass of soil or regolith becomes saturated with water and suddenly flows downhill to the base of the slope.
B)A block or blocks of unconsolidated regolith slide downhill along a curved slip surface.
C)The soil and regolith move downhill very slowly.
D)Blocks of hard bedrock rapidly slide downhill along fracture surfaces.

Question 15

How do the strength and cohesion of clay- rich regolith or soil change with the addition of water?

A)Water lowers the strength and cohesion.
B)Water does not affect the cohesion but lowers the strength.
C)Water reduces the strength of clays but raises the cohesion of the soil.
D)Water increases the strength and cohesion.

Question 16

The most rapid type of mass movement is a _ .

A)debris flow
B)lahar
C)slump
D)rock avalanche

Question 17

involves movement on a zone of compressed air.

A)Soil creep
B)A mudflow
C)A rock avalanche
D)A slump

Question 18

What caused the mudflows (1985)on the Nevado del Ruiz volcano?

A)Warm weather caused rapid melting of snow and ice near the summit.
B)Hot ash fell onto snow near the summit.
C)A crater lake was broken during an eruption.
D)all of the above

Question 19

denotes the exposed, crescent- shaped rupture surface at the head of a slump.

A)Scarp
B)Sole
C)Scoop
D)Toe

Question 20

Of the following, which one would most likely be triggered by an earthquake?

A)soil creep
B)slump
C)solifluction
D)rock avalanche

Question 21

denotes the downslope movement of soils and regolith.

Question 22

Which one of the following materials has the maximum, sustainable, slope angle, as determined by the angle of repose?

A)moist, clay- rich shale layers
B)dry silt
C)moist, sandy soil with a clay- rich matrix
D)dry sand

Question 23

denotes the exposed portion of the slip surface beneath a slump block.

Question 24

Based on the examples and discussion in chapter 12, what is the relationship of climate to mass wasting? Also, are certain climates more susceptible to mass wasting? Why?

Question 25

Talus slopes are associated with what type of motion-a fall, a slide, or a flow?

Question 26

a. slope angle b. water c. vegetation d. earthquake

Question 27

What is another name for volcanic mudflows, like those formed during the Mount St. Helens and Nevado del Ruiz eruptions?

Question 28

As a geologist working in a foreign country for the first time, you are asked to assess the potential for rapid mass wasting in a particular region. In what aspects or characteristics (geologic, geographic, biologic, etc.)of the region do you need for your assessment? Also, how could you possibly determine if mass wasting has been active in the recent geologic past (hundreds or thousands of years)?

Question 29

Which of the following was a major factor leading to the Gros Ventre, Wyoming, slide?

A)Dry weather caused the clay- rich strata to compact, allowing the overlying sandstone to slide into the valley.
B)Soils and shallow bedrock were very wet and locally saturated.
C)Erosion by the river had undercut the slope- forming shale and exposed the underlying sandstone.
D)A strong earthquake caused the unstable rock layers to move.

Question 30

Which process of mass wasting occurs primarily in permafrost regions?

Question 31

Where do the most rapid mass- wasting events occur?

A)gently sloped mountains
B)rugged, geologically young mountains
C)older, gradually sloped mountains
D)areas with a high occurrence of earthquakes

Question 32

is the basic force that moves or accelerates soil and regolith down a slope.

Question 33

What process of mass wasting is illustrated in the diagram below?

Question 34

Although it was not discussed in chapter 12, what are some preventive measures that can be done to reduce or lessen the impact of mass wasting? (Hint: Think about the controls and triggers of mass wasting.)

Question 35

What is the fastest moving of the mass wasting processes?

Question 36

Unconsolidated, granular materials such as gravel and sand will support maximum slope angles of about 33 to 35 degrees. What is the name for this maximum slope angle?

Question 37

involves the downslope movement of a block or blocks of unconsolidated soil and regolith along a curved, slip surface.

Question 38

As an erosional process, how is mass wasting unique from wind, water, and ice?

A)Mass wasting affects particles of all sizes whereas the others affect only smaller particles.
B)Mass wasting affects much larger geographic areas than does wind, water, and ice.
C)Mass wasting does not require a transporting medium.
D)All of the above make mass wasting unique compared to wind, water, and ice.