Deck 10: Mass Wasting

Question 1

What factors contribute to mass wasting in tropical versus arid and semiarid climates?

Answer 1

In the tropics, high temperatures and rainfall extend weathering to depths of tens of meters, and mass movements are common in the deep weathering zone. In arid and semiarid regions, the weathering zone is much shallower, but a short period of intense rain falling on a slope with little vegetation to absorb the water can also cause rapid runoff and mass wasting.

Question 2

Compare and contrast mudflows, debris flows, and earthflows.

Answer 2

Mudflows consist of small particles (at least 50% silt and clay) with a significant amount of water. They are common in arid and semiarid environments where occasional heavy rainfalls mix with slope material. Debris flows consist of larger particles with less water; they are more viscous and are slower. Earthflows are even slower; material slumps from the upper part of a hillside. They are more common in humid climates on grassy, soil-covered slopes following heavy rains.

Question 3

How does the geology (dip of rock layers or joints) on a slope affect slope stability?

Answer 3

If the rocks underlying a slope dip in the same direction as the slope, water can percolate along the various bedding planes and decrease the cohesiveness and reduce friction between adjacent rock layers. If joints dip in the same direction as the slope, water may seep through the joints in the rocks that would result in freezing and thawing during winter, which would crack open the rocks rendering them unstable.

Question 4

What is the angle of repose for a slope? What forces are acting? What numerical value does this angle have?

Question 5

How does gravity affect a slope?

Question 6

What factors played a role in the tragic rockslide at Frank, Alberta, Canada, in 1903?

Question 7

How does vegetation affect slope stability? What happens if vegetation is removed from the slope?

Question 8

What are quick clays, and how do they cause damage?

Question 9

What is shear strength? What factors collectively define a slope's shear strength?

Question 10

What is the effect of reducing water on a slope to mass movements? How can this be done?

Question 11

Briefly explain why saturated clays are considered as very unstable slope materials.

Question 12

What are some ways by which a slope can become oversteepened? How can oversteeping cause mass wasting?

Question 13

How can areas with high potential for slope failure be identified?

Question 14

Why is the California coastline so susceptible to losses (both property and monetarily) due to mass wasting? Put together what you've learned so far for the answer.

Question 15

Why is there sometimes a wire mesh covering the sides of a steep slope? What are the characteristics of the type of mass wasting this is meant to prevent?

Question 16

What role does weathering play in mass wasting?

Question 17

How would reducing the angle of slope in a hillside help to stabilize it? What two methods can be used to reduce a slope's angle?

Question 18

In what ways are slope-stability maps useful to planners and developers?

Question 19

What is permafrost, and what problems are associated with construction in a permafrost environment?

Question 20

Compare and contrast rapid mass movements and slow mass movements.

Question 21

Short Answer
What is mass wasting?

Question 22

What climatic conditions are most conducive to solifluction?

Question 23

How can slow mass movements be detected?

Question 24

What types of changes in a slope can lead to mass wasting?

Question 25

Because water can be so important in mass movement, what is one of the most effective and inexpensive ways of reducing mass wastage risk and damage?

Question 26

How can vegetation affect the likelihood of mass wasting?

Question 27

How does water content affect mass wasting?

Question 28

What is the most important step that can be taken to minimize mass wasting or damage from it?

Question 29

How can overloading affect slope stability?

Question 30

What is a slope-stability map?

Question 31

How does weathering promote mass wasting?

Question 32

What methods can be used to stabilize a hillside?

Question 33

Which of the following mass wasting phenomena (flow, slide, fall, creep) has the fastest rate of flow and why?

Question 34

How does a slump differ from a rock slide?

Question 35

What is meant by the term "flow" when used with reference to mass movements?

Question 36

What human activities contribute to or cause mass wasting?

Question 37

Give an example of a way in which mass wasting can affect human life.

Question 38

If you were surveying hillside property on which you planned to build a home, what are some of the evidences of former mass wasting you would pay attention to?

Question 39

How does a mudflow differ from a debris flow?

Question 40

On the basis of what three criteria are mass movements classified?

Question 41

The downward movement of material along a curved surface of rupture, which is characterized by the backward rotation of the displaced block, is called a(n) ____________________.

Question 42

The fundamental cause of mass wasting is ____________________.

Question 43

A rapid downslope mass movement of snow and ice is called a(n) ____________________.

Question 44

Creep is most effective and significant in a(n) ____________________ climate.

Question 45

Additional weight added to a hillside, which is always the result of human activities, is called ____________________.

Question 46

A general term for mass movements of Earth is ____________________.

Question 47

In the ____________________ and ____________________ method of protecting slopes, material is removed from the top of the slope and used as fill at the base.

Question 48

Curved tree trunks, displaced monuments, tilted power poles, displaced and tilted fences, roadways moved out of alignment, and hummocky surfaces are all evidence of ____________________.

Question 49

Mass movements in which rocks freefall through the air are known as ____________________.

Question 50

All slopes are constantly adjusting to new conditions referring that they are in a state of ____________________.

Question 51

Movement that is made of more than one type of mass wasting, each of which are more or less equally involved, is called ____________________ movement.

Question 52

____________________ can be constructed to provide support to the base of a slope. They are anchored into bedrock, backfilled with crushed rock, and provided with drain holes to prevent buildup of water pressure in the hillside.

Question 53

Clays that spontaneously liquefy and flow like water are called ____________________ clays.

Question 54

Completion
Geologists call the downslope movement of material under the direct influence of gravity ____________________.

Question 55

The material accumulated at the base of cliffs where rocks fall is known as ____________________.

Question 56

The downslope movement of water-saturated surface sediment is called ____________________.

Question 57

Mass movements in which material flows as a viscous fluid or displays plastic movement are termed ____________________.

Question 58

In the ____________________ method of protecting slopes, steps are cut into a hillside to reduce the overall average slope and catch small landslides or rockfalls.

Question 59

Ground that remains permanently frozen is called ____________________.

Question 60

A type of mass wasting that forms quickly, moves rapidly, and transports both small and very large objects and can be very dangerous are ____________________.

Question 61

Mudflows are particularly common in climates that are:

A) humid and warm.
B) temperate.
C) arid to semiarid.
D) cool.
E) very rainy.

Question 62

Mass wasting is more likely to occur in:

A) heavily weathered material.
B) thin layers of loose material.
C) bedrock.
D) well-sorted material.
E) material of large grain size.

Question 63

Overloading of a slope is rarely the fault of human action.

Question 64

Most mass wasting is enhanced or promoted by:

A) erosion.
B) weathering.
C) flash floods.
D) wind erosion.
E) plate tectonics.

Question 65

Among the types of slides are:

A) slumps.
B) block slides.
C) mudflows.
D) slumps and block slides.
E) slumps, block slides, and mudflows.

Question 66

Mass wasting is most likely to occur in:

A) arid warm regions.
B) humid tropical regions.
C) arctic regions.
D) temperate regions.
E) none of the above

Question 67

A rainstorm can trigger the landslide of an unstable slope.

Question 68

Some mass wasting occurs at almost imperceptibly slow rates.

Question 69

Permafrost lies beneath ____% of the land surface on Earth.

A) 0
B) 10
C) 20
D) 40
E) 50

Question 70

The type of mass wasting that is responsible for the greatest amount of monetary damage is:

A) creep.
B) slumps.
C) rockfall.
D) slides.
E) avalanches.

Question 71

Multiple Choice Landslides can be caused by:

A) earthquakes.
B) volcanic eruptions.
C) natural causes.
D) human activity and poor engineering.
E) all of the these

Question 72

Creep occurs only on weathered or soil-covered surfaces of moderate slope.

Question 73

All other factors being equal, the chance of mass wasting is increased by:

A) the amount of material involved.
B) the lack of friction on the slope.
C) the angle of the slope.
D) the kind of event that initiates the mass wasting.
E) whether there exists a positive or negative gravity anomaly.

Question 74

The removal of vegetation is a significant cause of slope failure and mass wasting.

Question 75

Mass movement that occurs along a curved surface of a rupture is known as:

A) rockfall.
B) slide.
C) creep.
D) slump.
E) none of these

Question 76

Mass wasting occurs on:

A) unstable material.
B) near-level slopes.
C) steep slopes.
D) gradual slopes.
E) all of these

Question 77

After gravity, the major cause of mass wasting is:

A) slope angle.
B) weakening by weathering.
C) overloading.
D) vegetation loss.
E) increased water content.

Question 78

A common triggering mechanism for mass wasting is:

A) vibrations due to earthquakes.
B) a sudden influx of excessive water.
C) erosion of the slope base.
D) vibrations due to earthquake and a sudden influx of excessive water.
E) vibrations due to earthquakes, a sudden influx of excessive water, and erosion of the slope base.

Question 79

The type of mass movement that moves the greatest amount of material downslope is:

A) creep.
B) slumps.
C) rockfall.
D) slides.
E) avalanches.

Question 80

The slow downslope movement of water-saturated surface sediment is:

A) quick clay.
B) solifluction.
C) creep.
D) slump.
E) earthflow.