Deck 13: Unsafe Ground: Landslides and Other Mass Movements

Question 1

Which of the following types of mass movement takes place most gradually?

A) slump
B) creep
C) rock slide
D) mudflow

Answer 1

B

Question 2

Which of the following types of mass movement is actually a landslide?

A) slump
B) creep
C) rock slide
D) mudflow

Answer 2

C

Question 3

Which of the following mass movements will include large identifiable fragments of bedrock?

A) slump
B) creep
C) rock slide
D) mudflow

Answer 3

C

Question 4

You use a drill rig to explore the subsurface of a large slope for ancient slumps and may encounter any of the following features downhole or in core samples you recover from the drill hole.Which feature is least likely to indicate a failure surface of the slump?

A) decayed leaves and grasses
B) a layer of conglomerate
C) a high flow of water at a specific depth
D) a layer of highly weathered, clay-rich regolith

Question 5

Which type of mass movement includes a large proportion of ash derived from a volcanic eruption?

A) stromboli
B) lahar
C) debris flow
D) wadi

Question 6

If the slump shown below had occurred many thousands of years before,and the head scarp and toe were no longer visible,how might you infer the presence of this slump?

A) Look for bent-over trees.
B) Look for sedimentary layers that were dipping at different angles from those nearby.
C) Look for an unusually steep slope.
D) Apply absolute age-dating techniques.

Question 7

____________occur(s)when a semicoherent mass of material moves downslope on a failure surface.

A) Avalanches
B) Slumps
C) Creep
D) Solifluction

Question 8

Which of these processes is illustrated in this diagram?

A) avalanches
B) slumping
C) creep
D) solifluction

Question 9

Large ____________ may trigger tsunamis.

A) lahars
B) submarine mass movements
C) avalanches
D) rockfalls

Question 10

A ____________ may form at the head of a slump.

A) toe
B) failure surface
C) scarp
D) mass

Question 11

Which of the following types of mass movement is the least coherent internally?

A) slump
B) creep
C) rock slide
D) mudflow

Question 12

One property that geologists use to distinguish among different types of mass wasting is the ____________ of the moving material.

A) weight
B) color
C) composition
D) name

Question 13

A rockslide into a reservoir triggered catastrophic flooding of the landscape below which dam?

A) Vaiont (Italy)
B) Aswan (Egypt)
C) Hoover (Nevada)
D) Glen Canyon (Arizona)

Question 14

Mass wasting always involves a sudden movement of material downslope.

Question 15

Slumps typically arrive intact at the bottom of a slope.

Question 16

The principal difference between a debris slide and a debris avalanche is the ____________.

A) straightness of the path taken by the moving mass
B) grain size of material within the moving mass
C) degree to which the displaced material remains internally coherent
D) presence of pyroclastic (volcanically ejected material) within a debris slide

Question 17

____________occur(s)when debris or snow mixes with air to form a chaotic cloud.

A) Avalanches
B) Slumps
C) Creep
D) Solifluction

Question 18

____________occur(s)where thawed sediments move downslope over permafrost.

A) Avalanches
B) Slumps
C) Creep
D) Solifluction

Question 19

A warming climate at both higher elevations and polar lattitudes would increase the extent or area in which solifluction occurs.
a.
true
b.
false

Question 20

All types of mass wasting have approximately the same velocities.

Question 21

____________ are unlikely to occur in regions without volcanic activity.

A) Lahars
B) Rockfalls
C) Submarine mass movements
D) Avalanches

Question 22

Which process is illustrated below?

A) landslide
B) lahar
C) rockfall
D) mudslide

Question 23

Fires and deforestation may lead to slope failure.

Question 24

Which of the following types of mass movement is likely to move most rapidly?

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

Question 25

____________ may form parallel to slope surfaces in granite and become a failure surface.

A) Bedding planes
B) Exfoliation joints
C) Foliation planes

Question 26

To the geologist,____________.

A) landslides and mass movements are the same thing
B) all mass movements are landslides, but not all landslides are mass movements
C) all landslides are mass movements, but not all mass movements are landslides
D) mass movements differ from landslides in that a greater mass of material moves during a mass movement than during a landslide

Question 27

Which of the following processes probably caused the failure of this riverbank in Costa Rica?

A) a combination of higher river level and stronger current after a recent storm
B) a lahar from one of Costa Rica's volcanoes
C) a rock slide triggered by an earthquake
D) soil creep

Question 28

All regions are susceptible to mass movements.

Question 29

____________ in sedimentary rock may become a failure surface.

A) Bedding planes
B) Exfoliation joints
C) Foliation planes

Question 30

The principal difference between a slump and a debris slide is the ____________.

A) shape of the path taken by the moving mass
B) grain size of the moving mass
C) slump's abundant water, compared to the dry debris slide
D) slump contains pyroclastic debris from a volcanic eruption

Question 31

The principal difference between a debris flow and a mudflow is the ____________.

A) shape of the path taken by the moving mass
B) clastic particles within the moving mass
C) debris flow's abundant water, compared to the dry mudflow
D) debris flow's pyroclastic debris content from a volcanic eruption

Question 32

Submarine mass movements have been found along hot-spot volcanoes and active plate boundaries.These massive slumps have been attributed to ____________.

A) subduction
B) earthquakes
C) mantle upwelling
D) liquefaction

Question 33

The principal difference between a lahar and a mudflow is the ____________.

A) shape of the path taken by the moving mass
B) grain size of the moving mass
C) lahar's abundant water, compared to the dry mudflow
D) lahar's pyroclastic debris content from a volcanic eruption

Question 34

The immediate cause of mass movement is ____________.

A) magnetic attraction
B) gravitational attraction
C) water content
D) frictional resistance

Question 35

Tectonic activity generally destabilizes slopes.

Question 36

Which of these factors would probably NOT help you distinguish between an ancient subaerial and a submarine mass movement preserved in lithified rock?

A) clam-like fossils in the deposit
B) clasts of sediment or sedimentary rock within the deposit
C) peat or coal within the deposit
D) a thick bed of evaporate deposits directly above the deposit

Question 37

The principal difference between a debris flow and a debris slide is the ____________.

A) shape of the path taken by the moving mass
B) grain size of the moving mass
C) debris flow's abundant water, compared to the dry debris slide
D) debris flow's pyroclastic debris content from a volcanic eruption

Question 38

____________ in metamorphic rock may become a failure surface.

A) Bedding planes
B) Exfoliation joints
C) Foliation planes

Question 39

You are mapping a new roadcut made through a wide,sloped plain.The roadcut exposes uniformly dipping sedimentary rocks.Which geologic feature listed below would indicate that creep had been occurring in the area before the roadcut was made?

A) a layer of rounded clasts in the bedrock
B) greater chemical weathering near the top of the newly exposed beds
C) a uniform tilting of the sedimentary beds toward the downslope direction of the sloped plain.
D) small ravines and ephemeral channels in the plain

Question 40

Which of the following increases the risk of mass movement?

A) adding a small amount of moisture to dry sediment
B) waves breaking on a beach before reaching a vertical sea cliff
C) saturating the sediment with water
D) reducing the steepness of the slope

Question 41

____________ may help stabilize slopes to prevent mass wasting.

A) Revegetation
B) Regrading
C) Preventing undercutting
D) All of the above are correct.

Question 42

During the last ice age it rained more in the southwest United States,compared to now.Which factor below would probably have DECREASED the likelihood that increased rainfall would have caused more slope failure?

A) increased plant growth resulting from increased precipitation
B) increased extent of frozen soils and solifluction
C) higher lake levels and groundwater levels
D) less precipitation of salts because of the higher ratio of rainfall to evaporation

Question 43

How could you distinguish a debris flow from a lahar?

A) Look for volcanic ash.
B) Look at the steepness of the failure surface.
C) Look for evidence of trees within the deposit.
D) All of the above are correct.

Question 44

Ground shaking can transform wet sediments into liquid-like slurries in a process known as ____________.

A) liquefaction
B) slumping
C) undercutting
D) sloping

Question 45

Which of the following factors decreases the risk of mass movement?

A) nearby earthquakes
B) excavation into the base of a hill
C) adding weight to the top of a hill
D) adding vegetation to the side of a hill

Question 46

Highway departments sometimes drill holes into roadside slopes excavated into regolith or weak rock.The holes are drilled to angle slightly upward from the curb,and after drilling is complete a perforated pipe is installed in each hole.How will this help stabilize the roadside slopes?

A) Air within the pipes will help dry out the slope.
B) Minerals will precipitate into the pipe where water enters it, making the slope stronger.
C) Air and bacteria that enter the hillside via the pipe will introduce rooting systems that will stabililize the slope.
D) Groundwater will flow into the pipes and drain out, thus decreasing the saturation of the slope.

Question 47

Why might a several-week rise in the Mississippi or Missouri River cause earthen levees (built of soil and sediment)along the riverbanks to fail?

A) The water tables in the levees would rise with the rising river levels
B) Floodwaters would drown plants on the levee banks, kill the plants and roots, and thereby decrease the soil-binding effects of the plant roots on the levees.
C) Rains would wash away the levees.
D) All of the above are correct.

Question 48

Which type of bedrock provides the greatest risk of landslide?

A) granite
B) gneiss
C) sandstone
D) shale

Question 49

The flow of water from a spring on a hillside increases.Why does this make the hillside less stable?

A) The increased spring flow will precipitate-out more minerals and make the slope heavier.
B) The increased spring flow will cool the hillside and discourage plant growth that normally stabilizes a hillside.
C) The increased spring flow will saturate more of the hillside and thereby increase its instability.
D) All of the above are correct.

Question 50

Which features in the figure are indicative of ongoing or recent slump movement?

A) dead trees
B) sinking foundations
C) tilted utility poles
D) All of the above are correct.

Question 51

The United States Geological Survey (USGS)sometimes issues debris flow advisories for parts of coastal California-much like the severe weather forecasts or flood forecasts that are issued for other regions of the country.Which one of these factors is the USGS unlikely to consider important in forecasting the likelihood of debris flows?

A) forecasted rainfall
B) the steepness of slopes in the area
C) the seasonal and diurnal variation in water uptake by plant root systems
D) the expected air temperatures

Question 52

Mixing gypsum,cement,or other materials into soils or regolith is a treatment sometimes used to increase the strength of the soil or regolith.What is one reason you might NOT want to apply this treatment to soil or regolith near the top of a roadside embankment?

A) The material you mix into the soil or regolith will harm plant root systems, and any plants that contributed to the stability of the slope will die.
B) If the soil or regolith has decreased permeability after you mix the material into it, water will drain out of it less easily and it will become more saturated over time.
C) Operating construction equipment near the top of a slope cannot be done safely.
D) If any of the gypsum, cement, or other material leaks out of the hillside, it will be dangerous to traffic on the road.

Question 53

Well-rounded sand has a gentler angle of repose than irregularly shaped gravel.

Question 54

Slope stability is determined by which two forces?

A) downslope and resistance
B) gravity and friction
C) resistance and gravity
D) downslope and friction

Question 55

Look at the remedial measures proposed for unstable grounds in the figures below.Which figures show the remedial measures that would have the most widespread applicability,be the least expensive,and be politically acceptable?

A) C and D
B) F and H
C) E and G
D) A and B

Question 56

Unstable slopes start to move when the ____________ force exceeds the ____________ force that holds the material in place.

A) downslope; gravity
B) resistance; downslope
C) downslope; resistance
D) gravity; resistance

Question 57

Moisture among sediment grains ____________.

A) always increases the likelihood of mass wasting
B) always decreases the likelihood of mass wasting
C) can promote stability if present in small amounts, but promotes mass wasting if sediment is saturated
D) can promote stability if the grains are saturated, but the presence of a small amount has little effect on the likelihood of mass wasting

Question 58

Conditions such as ____________ may exacerbate a developing slump.

A) persistent rain
B) rising floodwaters
C) earthquake aftershocks
D) All of the above are correct.

Question 59

For dry sediments,the angle of repose is usually between ________ and _______ degrees.

A) 10; 17
B) 17; 27
C) 30; 37
D) 30; 45

Question 60

Why would a slope be more prone to slumping after storm A (ten successive days of 1/3-inch of rain every day)in comparison to storm B (a five-hour storm that totals 6 inches of rainfall)?

A) In storm A, much of the water is likely to run off and not percolate into the slope.
B) In storm A, the rainfall is slow and steady enough for nearly all of it to percolate into the slope.
C) In storm B, debris flows might occur rather than slumps.
D) All of the above are correct.