Earth: An Introduction to Physical Geology, 11e (Tarbuck)
Chapter 15 Mass Wasting
15.1 Multiple-Choice Questions
1) ________ is the downslope movement of rock, regolith, or soil under the direct influence of
gravity.
A) Mass Wasting
B) Erosion
C) Weathering
D) Dissolution
2) What non-geologic term is commonly used to describe a sudden event in which large volumes
of material move down steep slopes?
A) Mass Wasting
B) Carbonization
C) Landslide
D) Lahar
3) Which of the following locations would be most likely to see large-scale, rapid mass wasting?
A) Florida Everglades
B) Central Illinois
C) Mojave Desert
D) Rocky Mountains
4) Which of the following factors does not influence mass wasting?
A) Gravity
B) Geologic age
C) Water
D) Vegetation
5) What is the angle of repose?
A) The angle of the slip plane from a slide
B) The steepest angle at which a material remains at rest
C) The angle of an inclined rock layer measured from a horizontal line
D) The angle of plunge into the interior
6) Which sediment size has the steepest angle of repose?
A) Gravel
B) Sand
C) Silt
D) Clay
7) Which of the following scenarios will be able to maintain the steepest angle of repose?
A) Wet sand-silt mix
B) Moist, clay-rich shale layers
C) Dry silt
D) Dry sand
8) A piece of gravel is resting on a slope. Which of the following best describes how the
gravitational force pulling the gravel downward will vary with the inclination of the slope?
A) Gravitational force is not affected by the slope angle
B) Gravitational force will increase as the slope angle decreases
C) Gravitational force will only change with the addition of water
D) Gravitational force will decrease as the slope angle decreases
9) What is the angle of repose for a larger sediment such as sand?
A) 7°
B) 12°
C) 33°
D) 42°
10) A stream is flowing over a hill composed of clay-rich soil. The stream is eventually blocked
to create a small pond in order to free land downhill for construction. What will happen to the
strength and cohesion of the soil in the area around this pond?
A) Strength and cohesion will decrease
B) Strength and cohesion will increase
C) Strength will decrease and cohesion will increase
D) Neither will be affected
11) A stream is cutting into a valley wall. Which of the following is the most likely trigger for a
mass-wasting event?
A) The stream will saturate the slope and generate a mudflow
B) The stream erodes the toe of the slope, which results in the slope becoming oversteepened
C) Upslope trees will be removed, reducing slope strength
D) The stream will deposit extra sediment on the slope, increasing the weight on the slope
12) Which of the following will not oversteepen a slope and lead to mass wasting?
A) Quarrying
B) Coastal erosion
C) Construction
D) None of the above
13) Which of the following is not a way an earthquake can trigger mass wasting?
A) Friction from the fault blocks grinding against each other reduces the angle of repose of slope
sediments
B) Shaking creates a landslide
C) Liquefaction caused sediments behave like fluids and move
D) Shaking created rock falls that blocked canyons, which led to later problems during flash
floods
14) Which slope composition is the most stable?
A) Unconsolidated sediments
B) Rock layers inclined parallel to the slope
C) Solid bedrock
D) Carbonate rock affected by dissolution
15) What is the fastest form of mass wasting?
A) Slide
B) Slump
C) Creep
D) Rockfall
16) What is the slowest form of mass wasting?
A) Slump
B) Debris Flow
C) Creep
D) Earthflow
17) What is the crescent-shaped mark found at the top of a slump block?
A) Scarp
B) Ditch
C) Overburden
D) Earthflow
18) Which mass-wasting process, generated on Nevado del Ruiz, destroyed the city of Armero in
1985?
A) Lahar
B) Rockfall
C) Solifluction
D) Debris Flow
19) What combination of factors was responsible for the Vaiont Dam disaster in Italy in October
1963?
A) Rockfalls filling the lake with debris until the water overtopped the dam and eroded through
the concrete
B) Water migrating along foliation layers in the metamorphic rock destabilized the dam, which
collapsed and flooded the valley
C) Heavy rains and the drawing down of the reservoir led to a landslide that filled the reservoir
and displaced the water
D) Drainage from the reservoir generated a lahar, which destroyed small towns downstream
20) Which sedimentary environment of deposition will be controlled in part by debris flows?
A) Fluvial
B) Dunes
C) Lacustrine
D) Alluvial fan
21) Which of the following types of flows will have the largest particle sizes?
A) Debris flow
B) Quick clay
C) Mudflow
D) Earthflow
22) What kind of sediment flow is found at the base of slump blocks?
A) Debris flow
B) Quick clay
C) Mudflow
D) Earthflow
23) Which of the following scenarios best describes the creation of the lahars associated with the
eruption of Mt. St. Helens in 1980?
A) Hot gases melted the volcano’s snowcap, generating meltwater that mixed with ash
B) A volcanic flank collapsed in a landslide, which flowed into Spirit Lake
C) Ash deposited during the eruption was remobilized by a flood years later
D) The volcanic dome exploded, depositing fine ash in the Toutle River
24) Which factor exerts the greatest control over the velocity of debris flows and the distance
they will travel?
A) Friction
B) Water content
C) Slope angle
D) Vegetation
15.2 True/False Questions
1) Mass wasting is possible only with the aid of a transportation agent such as water, wind, or
ice.
2) Low, old, rounded terrain is actively undergoing mass wasting.
3) Rapid mass-wasting events do not always need a trigger.
4) Triggers are the first step in a mass wasting event that leads to great damage.
5) Post-fire debris flows are most common in the first two years after a fire.
6) Frost action will make a slope less stable.
7) Grasses will create more slope stability than trees because there are more individual plants.
8) Thick deposits of soil over bedrock are more stable than thin deposits over bedrock.
9) When the slope is composed of layers of sedimentary rock, the most stable slope orientation is
when the planes of weakness between the layers are at right angles to the slope.
10) Solifluction is a slow type of mass wasting that moves at a rate of a few centimeters per year.
11) Rockfalls are the primary way in which talus slopes are built and maintained.
12) Mudflows are big enough to move independently of the topography.
13) Slow forms of mass wasting such as creep and solifluction are considered slow because they
are restricted to gentle slopes and cannot achieve the same velocity.
14) Solifluction occurs during the warmer months of the melt season.
15) Hummocky terrain is a sign of a landscape undergoing creep.
16) Creep is the most widespread mass-wasting process.
15.3 Short Answer Questions
1) What is the controlling force of mass wasting?
2) Evaluate the statement, “Weathering alone does not produce significant landforms” in the
context of mass wasting.
3) What are three examples of pre-existing slip planes for translational slides?
4) Why can rock avalanches move at such high speeds?
5) Southern California is famous for its wildfires that are often exacerbated by the Santa Ana
winds blowing through the canyons. What mass-wasting event will devastate the same area in
those fire-affected areas?
6) Consider the climate and weather patterns of the area where your school is located. At what
time of year would mass wasting be most likely?
7) In what climates is solifluction prevalent?
8) Why won’t meltwater infiltrate into permafrost?
15.4 Matching Questions
Match the type of motion with the correct definition.
A) Detached material moves in a free-fall
B) Mass movements in which there is a distinct plane of weakness between the slide material and
underlying stable material
C) Material moves downslope as a viscous fluid
1) Fall
Diff: 1
Bloom’s Taxonomy: Knowledge
Global Sci Out: 7
Section: 15.3 – Classification of Mass-Wasting Processes
Focus/Concepts: 15.3
Earth Science LO: 4.8 – Weathered and unstable rock materials erode from some parts of Earth’s
surface and are deposited in others.
2) Slide
Diff: 1
Bloom’s Taxonomy: Knowledge
Global Sci Out: 7
Section: 15.3 – Classification of Mass-Wasting Processes
Focus/Concepts: 15.3
Earth Science LO: 4.8 – Weathered and unstable rock materials erode from some parts of Earth’s
surface and are deposited in others.
3) Flow
Diff: 1
Bloom’s Taxonomy: Knowledge
Global Sci Out: 7
Section: 15.3 – Classification of Mass-Wasting Processes
Focus/Concepts: 15.3
Earth Science LO: 4.8 – Weathered and unstable rock materials erode from some parts of Earth’s
surface and are deposited in others.
16
Match the mass wasting process with the correct definition.
A) Material moving as an intact mass along a flat slip plane
B) Movement of detached materials through open air
C) Soil saturated with water flows downslope in permafrost areas
D) Material moves as an intact mass along a curved slip plane
E) Gradual movement of sediment due to repeated freezing and thawing
4) Rockfall
Diff: 1
Bloom’s Taxonomy: Knowledge
Global Sci Out: 2
Section: 15.4 – Rapid Forms of Mass Wasting & 15.5 – Slow Movements
Focus/Concepts: 15.4 & 15.5
Earth Science LO: 4.8 – Weathered and unstable rock materials erode from some parts of Earth’s
surface and are deposited in others.
5) Creep
Diff: 1
Bloom’s Taxonomy: Knowledge
Global Sci Out: 2
Section: 15.4 – Rapid Forms of Mass Wasting & 15.5 – Slow Movements
Focus/Concepts: 15.4 & 15.5
Earth Science LO: 4.8 – Weathered and unstable rock materials erode from some parts of Earth’s
surface and are deposited in others.
6) Solifluction
Diff: 1
Bloom’s Taxonomy: Knowledge
Global Sci Out: 2
Section: 15.4 – Rapid Forms of Mass Wasting & 15.5 – Slow Movements
Focus/Concepts: 15.4 & 15.5
Earth Science LO: 4.8 – Weathered and unstable rock materials erode from some parts of Earth’s
surface and are deposited in others.
7) Rockslide
Diff: 1
Bloom’s Taxonomy: Knowledge
Global Sci Out: 2
Section: 15.4 – Rapid Forms of Mass Wasting & 15.5 – Slow Movements
Focus/Concepts: 15.4 & 15.5
Earth Science LO: 4.8 – Weathered and unstable rock materials erode from some parts of Earth’s
surface and are deposited in others.
8) Slump
Diff: 1
Bloom’s Taxonomy: Knowledge
Global Sci Out: 2
Section: 15.4 – Rapid Forms of Mass Wasting & 15.5 – Slow Movements
Focus/Concepts: 15.4 & 15.5
Earth Science LO: 4.8 – Weathered and unstable rock materials erode from some parts of Earth’s
surface and are deposited in others.