Question 1

How do the strength and cohesion of clay-rich regolith or soil change with the addition of water?
A)Water does not affect the cohesion but lowers the strength.
B)Water reduces the strength of clays but raises the cohesion of the soil.
C)Water increases the strength and cohesion.
D)Water lowers the strength and cohesion.

Accepted Answer

With the addition of water, clay-rich regolith or soil experiences a decrease in strength and cohesion. This is because water acts as a lubricant, reducing the friction between particles and making it easier for them to move past each other. The result is a loss of stability and ability to support weight or retain its shape.

Question 2

When descending cohesive material moves "en masse" along a curved surface of rupture that just formed, it is termed a ________.
A)creep
B)flow
C)slump
D)sag

Accepted Answer

This description is characteristic of a slump, which occurs when a cohesive mass of material slides down a curved slope or hillside. Creep refers to the slow, gradual downslope movement of soil or rock, flow typically involves the movement of unconsolidated material like sand, and sagging refers to the bending or dropping of a surface due to weight or pressure.

Question 3

What will the long term effect of mass wasting be on oversteepened slopes?
A)It will cause the steep slopes to retreat uniformly, widening the valley but keeping the steep slopes at the margins.
B)It will eventually restore an equilibrium profile by reducing the slope angle.
C)It will fill in the lowland up to the level of the surrounding highland region.
D)It will perpetuate catastrophic mass failures until the entire highland region is removed

Accepted Answer

Mass wasting will continue to occur until the slope angle is reduced to a more stable level. This process may take a long time, but eventually the oversteepened slopes will be levelled out through repeated mass wasting events. This will restore an equilibrium profile and reduce the frequency and severity of mass wasting events. Options A, C, and D are not likely outcomes of long-term mass wasting on oversteepened slopes.

Question 4

The angle of repose in unconsolidated materials varies from ________ depending on the size and cohesion of particles.
A)2.5° to 4.0°
B)5° to 14°
C)25° to 40°
D)50° to 90°

Accepted Answer

The angle of repose in unconsolidated materials typically ranges from 25° to 40°, depending on the size and cohesion of the particles. Option A and B are too low and option D is too high for the range.

Question 5

Which statement best describes slumping, a mass wasting process?
A)A block or blocks of rock and/or unconsolidated regolith slide downhill along a curved slip surface.
B)Blocks of hard bedrock rapidly slide downhill on the slope surface.
C)The soil and regolith move downhill very slowly.
D)A mass of soil or regolith becomes saturated with water and suddenly flows downhill to the base of the slope.

Accepted Answer

Slumping involves a block or blocks of material moving downhill along a curved slip surface, which distinguishes it from other types of mass wasting by the shape of the moving mass and the path it takes.

Question 6

Which one of the following materials has the maximum, sustainable, slope angle, as determined by the angle of repose?
A)unfractured granite
B)moist, sandy soil with a clay-rich matrix
C)dry sand
D)unsorted, crushed rock used for highway paving

Accepted Answer

Dry sand has a low cohesive strength and a high angle of repose, resulting in a maximum sustainable slope angle. The other materials have higher levels of cohesion and lower angles of repose, making them less suitable for steep slopes.

Question 7

Which natural factors routinely weaken slope materials and make them more prone to mass wasting and failure?
A)ablation, chemical weathering, and terracing of slopes
B)devegetation, oversteepening, saturation, and vibrations
C)erosion, sedimentation, and lithification
D)temperature changes and tidal variations in gravitational acceleration

Accepted Answer

Devegetation removes the stabilizing effect of plant roots and increases the potential for slope failure. Oversteepening occurs when a slope is steepened beyond the angle of repose, leading to instability. Saturation can occur from heavy rainfall or snowmelt, reducing the strength of the slope material. Vibrations from earthquakes or human activities can also weaken the slope and make it more prone to failure.

Question 8

What is the major and immediate controlling force in mass wasting?
A)Chemical weathering as bonds fall apart, weakening minerals.
B)Convection, as this drives mantle convection and tectonic uplift.
C)Coriolis force, as it controls cyclonic winds and transport of precipitation.
D)Gravity, as this pulls matter downhill.

Accepted Answer

Gravity is the major and immediate controlling force in mass wasting, as it causes the downhill movement of materials.

Question 9

How do forest or wild fires contribute to mass wasting?
A)by removing stabilizing vegetation
B)via wind transport of fines during the fire
C)by unloading the slope and reducing the rate of mass wasting
D)Human disturbance caused by fire fighting activities is the most destructive and leads to further slope failures.

Accepted Answer

Forest or wild fires contribute to mass wasting by removing the stabilizing vegetation that holds the soil and rock in place. Without vegetation, water can infiltrate the soil more easily, making it more susceptible to erosion and mass wasting. This can lead to landslides, rockfalls, and debris flows.

Question 10

All of the following are factors affecting mass wasting except for ________.
A)gravity
B)water
C)slope angle
D)geologic age

Accepted Answer

Geologic age is not a factor affecting mass wasting. The other factors (gravity, water, and slope angle) can all play a role in the occurrence and intensity of mass wasting events.

Question 11

How does water affect the internal cohesion of clay-bearing soils and regolith?
A)The soil or regolith has more internal cohesion when wet than when dry.
B)The soil or regolith has less internal cohesion when wet than when dry.
C)The soil or regolith has equal internal cohesion when wet or dry.
D)The soil or regolith has no internal cohesion when wet or dry.

Accepted Answer

Water acts as a lubricant between the clay particles, reducing the friction and thus the internal cohesion of clay-bearing soils and regolith when they are wet compared to when they are dry.

Question 12

Excavated road cuts or quarry faces, and eroding natural river bluffs and sea cliffs, are all examples of ________ which can lead to mass wasting.
A)landscape stabilization
B)oversteepening
C)lithospheric hydration
D)vivisection

Accepted Answer

Oversteepening, or steepening a slope beyond its natural angle of repose, can occur through excavation or erosion of a slope. This increases the likelihood of mass wasting, as the slope is no longer stable under its own weight. The other choices are not related to the phenomenon of mass wasting.

Question 13

How are talus slopes built?
A)by glacial transport
B)by rock falls
C)by debris flows
D)between major earthquakes by intense low temperature chemical weathering

Accepted Answer

Talus slopes are typically built by the accumulation of rockfall debris that has fallen from the slopes above. As rocks weather and erode, they break apart and fall down the slope. Over time, the accumulation of fallen rocks can form a steep and unstable talus slope. Glacial transport and debris flows are also involved in the formation of some talus slopes, but rockfalls are the primary mechanism in most cases. Intense low temperature chemical weathering does not build talus slopes.

Question 14

________ describes the downslope movement of cohesive material along a well defined surface such as a joint or a bedding plane.
A)Avalanche
B)Fall
C)Slide
D)Woo hoo!

Accepted Answer

The term that best describes this type of downslope movement is slide. This is because the cohesive material moves along a well-defined surface, such as a joint or a bedding plane, rather than moving freely (like in a fall or avalanche). It is a slow movement and does not involve free-fall. "Woo hoo!" is not a relevant answer.

Question 15

How do mass wasting processes differ from erosional ones?
A)Mass wasting is always very fast and catastrophic whereas erosion is always slow and gradual.
B)Erosion usually requires steep slopes whereas mass wasting can happen even on flat terrains.
C)Mass wasting is a spring and summer phenomenon while erosion is year around.
D)Mass wasting does not require a transport agent such as wind, water, or glacial ice.

Accepted Answer

Mass wasting involves the movement of rock and soil down slopes due to gravity alone, without the need for a transporting medium like wind, water, or ice, which are essential for erosion processes.

Question 16

Frost wedging and thawing on vertical cliffs produces ________.
A)alluvial fans
B)debris flows and torrents
C)fast moving rock glaciers
D)talus cones

Accepted Answer

Frost wedging and thawing on vertical cliffs causes individual blocks of rock to break loose and fall downward due to gravity. These blocks create talus cones at the base of the cliff as they accumulate over time. Alluvial fans are formed by the deposition of sediment from flowing water, while debris flows and torrents typically occur in steep, confined channels, and fast-moving rock glaciers are typically found in high-altitude regions and are formed from a combination of ice and rock.

Question 17

What two properties of rain water and snow melt have the greatest effect on soil strength and slope stability?
A)acidity and strong dipole forces
B)electric conductivity and viscosity
C)increased lubrication and added weight
D)solvation properties and surface tension

Accepted Answer

Rain water and snow melt can increase lubrication and add weight to soil, which can greatly affect its strength and slope stability. This is because wet soil is less able to hold its shape and support weight, making it more prone to erosion and landslides.

Question 18

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 increase as the slope angle is decreased.
B)It will decrease as the slope angle is decreased.
C)It is not affected by the slope angle.
D)It will decrease as the slope angle is increased.

Accepted Answer

The gravitational force is dependent on the weight of the particle and the angle of the slope. As the slope angle is decreased, the component of gravitational force pulling the particle along the land surface decreases, resulting in a decrease in overall gravitational force. Therefore, as the slope angle is decreased, the gravitational force pulling the particle downward also decreases.

Question 19

Which statement best describes liquefaction?
A)Upon intense shaking, surface materials lose their strength and behave as fluid-like masses that flow.
B)High volumes of liquid are injected into the ground, eliminating its cohesion.
C)Coal beds are heated and liquified for fuel.
D)Deep-sea sediments lose water during subduction which liquefies overlying mantle rock.

Accepted Answer

Liquefaction occurs when intense shaking causes loosely packed surface materials to lose their strength and act as fluid-like masses that flow. This can lead to soil liquefaction and the formation of features like sand volcanoes and lateral spreading. Options B, C, and D do not accurately describe liquefaction.

Question 20

What do slumps, rockslides, debris flows and earthflows all have in common?
A)They all happen in frozen soils on steep slopes.
B)They all require water for lubrication.
C)They all transport on a cushion of compressed air.
D)They are all forms of mass wasting.

Accepted Answer

Slumps, rockslides, debris flows and earthflows are all different types of mass wasting (also known as landslides).

Quiz 14: Mass Wasting: The Work of Gravity

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

When descending cohesive material moves "en masse" along a curved surface of rupture that just formed, it is termed a ________.

What will the long term effect of mass wasting be on oversteepened slopes?

The angle of repose in unconsolidated materials varies from ________ depending on the size and cohesion of particles.

Which statement best describes slumping, a mass wasting process?

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

Which natural factors routinely weaken slope materials and make them more prone to mass wasting and failure?

What is the major and immediate controlling force in mass wasting?

How do forest or wild fires contribute to mass wasting?

All of the following are factors affecting mass wasting except for ________.

How does water affect the internal cohesion of clay-bearing soils and regolith?

Excavated road cuts or quarry faces, and eroding natural river bluffs and sea cliffs, are all examples of ________ which can lead to mass wasting.

How are talus slopes built?

________ describes the downslope movement of cohesive material along a well defined surface such as a joint or a bedding plane.

How do mass wasting processes differ from erosional ones?

Frost wedging and thawing on vertical cliffs produces ________.

What two properties of rain water and snow melt have the greatest effect on soil strength and slope stability?

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?

Which statement best describes liquefaction?

What do slumps, rockslides, debris flows and earthflows all have in common?