Deck 16: Unsafe Ground: Landslides and Other Mass Movements

Question 1

________ occurs when debris or snow mixes with air to form a chaotic cloud.

A) An avalanche
B) A slump
C) Creep
D) Solifluction

Answer 1

A

Question 2

Geologists distinguish among different types of mass wasting based on factors such as the ________ of the moving material and the rate of movement.

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

Answer 2

C

Question 3

Identify the failure surface in the image below.

A) A
B) B
C) C
D) D

Answer 3

C

Question 4

The downslope movement of which of the following materials does NOT constitute a mass wasting event?

A) water
B) snow
C) ice
D) rock

Question 5

Which of the following types of mass movement often travels down a curved surface?

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

Question 6

Identify the toe of the slump in the image below.

A) A
B) B
C) C
D) D

Question 7

Which of the following types of mass movement is least coherent (most fluid-like)?

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

Question 8

Lahars occur on ________.

A) volcanic slopes
B) vertical cliff faces
C) undersea slopes
D) divergent plate boundaries

Question 9

What type of mass wasting event is beginning to form on the hillside shown in the image below?

A) an avalanche
B) a debris flow
C) solifluction
D) a slump

Question 10

A ________ may form at the head of a slump.

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

Question 11

Mass movements are driven by __________.

A) the addition of moisture
B) friction
C) cohesion
D) gravity

Question 12

Why do submarine slumps pose a hazard to people living in coastal areas?

A) Submarine slumps can trigger other mass movements on land.
B) Submarine slumps can induce liquefaction of the nearby land surface.
C) Submarine slumps can trigger tsunamis.
D) Submarine slumps can trigger earthquakes.

Question 13

The principal difference between a debris flow and a mudflow is ________.

A) the shape of the path taken by the moving mass
B) the grain size of the moving mass
C) that a debris flow contains abundant water,whereas a mudflow is dry
D) that a debris flow contains pyroclastic debris from a volcanic eruption

Question 14

Slumps typically arrive ________ at the bottom of a slope.

A) vertically stacked
B) intact
C) flattened
D) jumbled

Question 15

Tree trunks that have a pronounced curvature at their base are indicative of ___________.

A) creep
B) an avalanche
C) solifluction
D) a slump

Question 16

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

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

Question 17

Regolith consists of __________.

A) large rock fragments
B) loose sediments
C) loose sediments and large rock fragments
D) loose sediments,large rock fragments,and water

Question 18

What is happening to the hillside in the tundra pictured below?

A) an avalanche
B) a debris flow
C) solifluction
D) a slump

Question 19

The principal difference between a slump and a debris slide is ________.

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

Question 20

The principal difference between a lahar and a mudflow is ________.

A) the shape of the path taken by the moving mass
B) the grain size of the moving mass
C) that the lahar contains abundant water,whereas the mudflow is dry
D) that the lahar contains pyroclastic debris from a volcanic eruption

Question 21

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 22

________ can occur where undercutting by waves removes support from beneath cliff overhangs.

A) Liquefaction
B) Lahars
C) Rock falls
D) Mudslides

Question 23

You are a geologist trying to determine if the slope your client's house sits on is stable.You determine that the angle of repose of the hillside is 35°.Which of the following situations would be considered stable?

A) The slope is composed of water-saturated sand.
B) The slope is composed of dry sand.
C) The slope is composed of very well-rounded sand.
D) The slope is composed of dry gravel.

Question 24

Which of the following situations would be the least susceptible to slope failure?

A) a gently sloping hill in a dry desert region
B) a gently sloping hill with a river at the bottom of the hill
C) a steeply sloping hill overlooking the ocean
D) a steeply sloping hill in a dry desert region

Question 25

Which of the following situations is the most likely candidate for the occurrence of mass movements?

A) a flat,desert area with little vegetation
B) a gentle slope along the coastline that is across a highway from the surf zone
C) gently sloping hills in the tropics
D) a mountain terrain in a humid environment

Question 26

The most important factor in determining if an area will be subject to mass movement is _______.

A) relief
B) gravity
C) weather
D) water content

Question 27

In a _________,submarine sediments flow chaotically downslope in submarine canyons.

A) turbidity current
B) tsunami
C) submarine debris flow
D) submarine slump

Question 28

Well-rounded sand has an angle of repose __________ that of irregularly shaped gravel.

A) greater than
B) less than
C) equal to
D) incomparable to

Question 29

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
D) can promote stability if the grains are saturated

Question 30

The immediate cause of incidents of mass movement is ________.

A) electromagnetic attraction
B) gravity
C) magnetism
D) friction

Question 31

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

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

Question 32

Weathering is a failure trigger because it ____________ of the material.

A) decreases the strength
B) increases the friction
C) decreases the weight
D) takes vegetation off

Question 33

Well-rounded sand has a smaller ________ than irregularly shaped gravel.

A) cohesion
B) angle of repose
C) mineral stability
D) cross-sectional area

Question 34

Adding a small amount of water to a substance increase its cohesion; whereas,adding a lot of water decreases its cohesion.Why?

A) A small amount of water decreases surface tension,allowing the grains to bond together,whereas too much water will increase surface tension and force the grains away from each other.
B) A small amount of water increases surface tension and holds the grain together.Too much water between the grains will eliminate surface tension.
C) Water has a small electrostatic force that disrupts the gravitational attraction of the grains and forces them to move away from each other.
D) A small amount of water will precipitate cement into the pores of the material,whereas too much water will not allow that cement to form.

Question 35

As shown in the figure below,________ may form parallel to slope surfaces in granite and become a failure surface.

A) bedding planes
B) exfoliation joints
C) foliation planes
D) uplift planes

Question 36

Liquefaction is most likely to occur in which type of area?

A) hills in Florida
B) the coast of California
C) the coast of Texas
D) a desert in California

Question 37

Which of the following increases the risk of mass movement?

A) adding a small amount of moisture to loose,dry sediment
B) waves breaking before they reach sea cliffs
C) flooding the sediment with water to the point of saturation
D) reducing the grade of the slope

Question 38

Why does the removal of material at the base of a slope decrease its stability?

A) Removing material decreases the surface tension between grains.
B) The force of gravity decreases,and the slope will fail.
C) The slope now has a much lower angle of repose.
D) The slope now exceeds the angle of repose.

Question 39

The ________ in the sequence of sedimentary rocks shown below may become a failure surface.

A) bedding planes
B) exfoliation joints
C) foliation planes
D) uplift planes

Question 40

Which of the following situations would be the most susceptible to slope failure?

A) a large mansion built on top of a gentle sloping hill covered with vegetation
B) a hotel built on a flat surface with a large river flowing next to the hotel
C) a large resort built on top of a cliff directly above the ocean
D) a small house built on top of a steep slope in a desert region

Question 41

Which of the following consist(s)of large boulders placed at the base of coastal slopes?

A) rock dams
B) rock sheds
C) riprap
D) retaining walls

Question 42

Which areas are most susceptible to slope failure?

A) water-saturated vertical road cuts
B) slopes at 30° next to rivers
C) saturated and vegetated slopes
D) unsaturated vertical road cuts

Question 43

Notice the cliff in the image below.Is this cliff stable? Why or why not? What could be done to increase the stability of the cliff?

Question 44

What is the most effective means of mitigating the risk of a slope failure for slope shown in the figure below?

A) applying shotcrete
B) revegetating with new plants
C) installing riprap
D) dewatering the slope

Question 45

What is a turbidity current? How is this related to mass movements?

Question 46

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 47

Construction workers often cut benches or terraces,such as those seen in the image below,along the sides of roads to help mitigate landslides.This is because terraces

A) provide flat areas where large trees and shrubs can be planted.
B) mitigate slope failure by removing weight from the hillside.
C) force cars to be farther from steep slopes that might fail.
D) allow flat areas where houses can be built without adding weight.

Question 48

Describe two ways of mitigating landslide hazards and describe how they work and what issues they may have.

Question 49

How can the amount of water play a role in slope stability and slope failure?

Question 50

Examine the photograph below.What type of mass wasting event is beginning to take place here? How can you tell?

Question 51

After finishing a new construction project,why is the first task often to install new landscaping around the area?

A) The plants will provide nutrients for animals that will carry away the soil.
B) The roots will grow into the slope and work to keep the slope intact.
C) The plants will add additional weight to the slope and keep it stable.
D) The roots take in oxygen and release it into the soil to increase surface tension.

Question 52

Slope failures are more likely to occur in ________ than in ________.

A) forests; deserts
B) mountains; deserts
C) deserts; mountains
D) deserts; forests

Question 53

Why would Florida,which receives plentiful rainfall and remains humid for a large portion of the year,be less susceptible to landslides than the California desert?

Question 54

What is the resistance force and how is it derived? What happens when the resistance force exceeds the downslope force? What happens when the downslope force exceeds the resistance force?

Question 55

How can you use a landslide hazard map to help buy a piece of property?

A) to determine if there are large rivers running by the property
B) to determine if the property is in a high-risk zone for landslides
C) to determine if the property is near a high-risk flood zone
D) to determine if the property has been exposed to fires recently

Question 56

Compare and contrast a debris flow and a debris fall.

Question 57

Describe two factors that affect the resistance force and explain how they affect the stability of the slope.

Question 58

In the figure below,what would be the most effective way to stabilize the slope,assuming that the slope is in a dry,desert environment?

A) regrading the slope
B) moving the road
C) adding more vegetation
D) installing riprap

Question 59

Why are submarine mass wasting events of concern to people living near sea level in coastal regions? (What hazard can be triggered by submarine mass wasting events?)

Question 60

Slope failures are most likely to occur in ________ conditions.

A) dry,mountainous
B) dry,flat
C) wet,mountainous
D) wet,flat