Deck 14: Mass Movement

Question 1

All of the following can be used to predict an immediate mass- movement event EXCEPT:

A) eyewitness observation of slowly accelerating creep.
B) previous or historic occurrences of such events.
C) strange animal behavior.
D) electric slide detectors.

Answer 1

B

Question 2

Large slump areas can be camouflaged beneath vegetation and creeping materials. These are best detected by using:

A) satellite imagery.
B) aerial photographs.
C) historical records.
D) seismic profiling.

Answer 2

B

Question 3

What is the cause of solifluction seen in very cold regions?

A) Summer thawing of permafrost.
B) Volcanic activity.
C) Tsunamis.
D) Movement on a fault.

Answer 3

A

Question 4

The first step in preventing mass- movement events is:

A) to determine how to reduce slope forces promoting mass movement.
B) investigation of subsurface geology in the area.
C) identification of potential trigger mechanisms in the region.
D) to determine how to enhance slope forces resisting movement.

Question 5

Which of the following best describes the magnitude of damage and death due to mass- movement events in the United States?

A) Mass movement causes virtually no damage or deaths.
B) Mass movement causes more damage and deaths than any other type of natural disaster.
C) Mass movement causes fewer deaths, but more damage than any other type of natural disaster.
D) Mass movement causes little damage, but more deaths than any other type of natural disaster.

Question 6

The principal factor driving mass movement is:

A) lack of cohesion in a slope.
B) friction.
C) gravity.
D) an unstable slope angle.

Question 7

Evidence of past slope failure is demonstrated by all of the following EXCEPT:

A) gently sloping, vegetated hillsides.
B) jumbles of slide and flow debris.
C) talus slopes.
D) landslide scars.

Question 8

All of the following events were associated with the Madison Canyon mass- movement event of 1959 EXCEPT:

A) a wall of water rushed over Hegben Dam.
B) a landslide moved downslope at 160km/hr.
C) lava was erupted from nearby fissures.
D) the soil surface rolled like sea waves.

Question 9

Risk- level maps issued by government agencies depicting mass- movement events are based on:

A) geologic evidence of previous slope failure.
B) eyewitness accounts.
C) analysis of possible triggering mechanisms.
D) terrain analyses.

Question 10

Mass- movement events on the Moon are triggered primarily by:

A) meteorite impacts.
B) the freezing and thawing of crater slopes.
C) volcanic eruptions.
D) moonquakes.

Question 11

Slopes composed of bedrock are most susceptible to mass movement when:

A) the rock is sedimentary, and the bedding planes lie parallel to the slope surface.
B) the rock is igneous and lacks joints or fractures.
C) the rock is metamorphic, and the foliation planes lie perpendicular to the slope surface.
D) the rock is igneous, and planes of weakness lie perpendicular to the slope surface.

Question 12

Ancient Martian mudflows most likely gained their water from:

A) melted snow from volcanic peaks.
B) torrential rains.
C) melted permafrost.
D) melted polar ice caps.

Question 13

All of the following are true of earthflows EXCEPT:

A) they are the fastest and most dangerous type of flow.
B) they do a great deal of damage to structures in their paths.
C) they consist of relatively dry masses of clayey or silty regolith.
D) they are highly viscous.

Question 14

The most common type of mass movement is:

A) fall.
B) flow.
C) creep.
D) slide.

Question 15

Underwater landslides on the southeastern flanks of the K'ilauea volcano are due to:

A) tsunamis.
B) inflation of the volcano before eruption.
C) explosive volcanic eruptions.
D) earthquakes.

Question 16

More than any other factor, can cause a previously stable slope to become unstable.

A) the addition of heavy loads
B) the burrowing of animals
C) the removal of vegetation
D) the addition of large amounts of water

Question 17

Which of the following represents a common relationship between types of mass movement?

A) Slides are often preceded by creep.
B) Falls are often preceded by slumps.
C) Falls are often preceded by slides.
D) Flows are often preceded by falls.

Question 18

All of the following indicate potential future mass movement EXCEPT:

A) steam emitted from the local soil.
B) displaced fence lines and bent tree trunks.
C) water leakage from swimming pools.
D) tilted utility poles and sagging power lines.

Question 19

Which of the following best describes the forces involved in the stability of a slope?

A) Gp pulls materials perpendicular to the slope; F pulls materials parallel to the slope; and Gd opposes motion between two bodies in contact.
B) pulls materials perpendicular to the slope; Gp pulls materials parallel to the slope; and Gd opposes motion between two bodies in contact.
C) Gp pulls materials parallel to the slope; Gd pulls materials perpendicular to the slope; and F opposes motion between two bodies in contact.
D) Gd pulls materials parallel to the slope; Gp pulls materials perpendicular to the slope; and F opposes motion between two bodies in contact.

Question 20

On a slope susceptible to mass movement, the best way to reduce the movement potential is to:

A) remove excess vegetation.
B) increase the angle of the slope.
C) freeze the slope with liquid nitrogen.
D) reduce the water content of the slope.

Question 21

Which of the following statements about the role of water in mass movement is NOT true?

A) A larger amount of water increases slope stability by increasing surface tension between adjacent particles.
B) A small amount of water increases slope stability by aiding the growth of vegetation.
C) A larger amount of water decreases slope stability by reducing friction between surface materials and the underlying material.
D) A small amount of water somewhat increases slope stability because the water's surface tension attracts particles.

Question 22

All of the following are true of lahars EXCEPT:

A) Mount St. Helen's eruption was accompanied by a lahar.
B) they occur only during a volcano's eruptive period.
C) their water content may be gained from rain caused by the volcanic eruption.
D) they are one of the fastest types of flows.

Question 23

The primary difference between slides and slumps is that:

A) slides move much more rapidly than slumps.
B) in slides, loose material behaves like a solid, and in slumps, loose material behaves like a liquid.
C) slides occur along a plane surface, and slumps occur along a curved surface.
D) slides involve fragments of bedrock, whereas slumps involve soil.

Question 24

Geologists can date mass- movement events by which of the following methods?

A) Lichenometry.
B) Dendrochronology.
C) C¹⁴ dating of organic materials.
D) All of the above.

Question 25

Vegetation hinders mass movement by:

A) halting the downslope flow of heavy rainfall.
B) decreasing the weight on the slope.
C) preventing slope steepening by natural or human causes.
D) binding and stabilizing the soil.

Question 26

All of the following are practical methods for reducing the water content of a slope EXCEPT:

A) constructing a perforated- pipe drainage system.
B) remove vegetation from slope.
C) covering the slope with sheets of plastic or a layer of concrete.
D) erecting a barrier to divert water away from a slope.

Question 27

All of the following are common human- induced triggers of mass movement EXCEPT:

A) diversion of surface water onto sensitive slopes at construction sites.
B) leaky septic fields.
C) removing material from slopes.
D) over- irrigation of slopes.

Question 28

Geologists classify mass movements based on:

A) the amount of material involved.
B) their speed and the manner of movement of the material.
C) the amount of damage incurred.
D) the distance the material travels.

Question 29

The city of La Conchita was located on an old landslide that was reactivated by:

A) an earthquake in the region.
B) high waves from the ocean.
C) road construction in the area.
D) heavy rains in the region.

Question 30

The steep, exposed cliff face that forms where a slump mass has pulled away from the rest of the slope is a:

A) talus slope.
B) joint.
C) slump block.
D) scarp.

Question 31

Loose, unconsolidated material will remain stable if the:

A) arrangement of the materials exceeds the angle of repose.
B) friction between the material and the slope equals the downslope component of gravity.
C) downslope component of gravity exceeds the friction between the material and the slope.
D) friction between the material and the slope exceeds the downslope component of gravity.

Question 32

All of the following are true of flows EXCEPT:

A) the most dangerous flows have a very high water content.
B) they are mixtures of solid particles that behave like a viscous fluid.
C) some flows can be relatively dry.
D) they are classified by speed and the angle of the underlying slope.

Question 33

Of the following types of mass movement, the fastest and slowest, respectively, are:

A) slide and slump.
B) fall and creep.
C) slide and solifluction.
D) fall and flow.

Question 34

Which type of mass movement moves along a concave surface?

A) Slump.
B) Creep.
C) Rock fall.
D) Slide.

Question 35

Which of the following conditions make rocks less stable in resisting downslope movement?

A) Chemical weathering produces solution cavities.
B) Mechanical weathering produces cracks in the rock.
C) Tectonic forces produce fractures.
D) All of the above.

Question 36

Natural triggers of mass- movements include all of the following EXCEPT:

A) torrential rains.
B) earthquakes.
C) intrusion of magma.
D) volcanic eruptions.

Question 37

The first clues to the future behavior of past or ongoing mass movements are often gained from:

A) information about the frequency of possible triggering mechanisms.
B) terrain analysis.
C) geological evidence of previous slope failure.
D) eyewitness accounts of unusual terrain behavior.

Question 38

The velocity of falls is very high because of the:

A) shape of rock masses.
B) steep slope angle.
C) acceleration of gravity.
D) type of rock involved.

Question 39

The best definition of mass movement is:

A) the transport of Earth materials by wind.
B) the transport of Earth materials downslope by the pull of gravity.
C) the transport of Earth materials by glaciers.
D) the transport of Earth materials by streams.

Question 40

All of the Earth systems promote mass movement events EXCEPT:

A) hydrosphere; erosion causes oversteepened slopes.
B) atmosphere; saturation of materials with water.
C) biosphere; binding effects of vegetation.
D) lithosphere; fracturing of rocks.

Question 41

A boulder is most likely to slide downhill if:

A) Gd is relatively high and F is relatively low.
B) Gd is relatively low and F is relatively high.
C) Gp is relatively high and Gd is relatively low.
D) Gp is relatively low and F is relatively high.

Question 42

Houses in California that are built on slopes that face the Pacific Ocean are frequently destroyed as a result of mass movement. Without knowing the specific geology of these slopes, what can you determine about the other factors likely to contribute to these mass movements?

Question 43

For dry sand, the angle of repose is generally in what range?

A) 10- 15°.
B) 30 to 35°.
C) 45- 50°.
D) 60- 70°.

Question 44

Discuss methods of preventing mass- movement events.

Question 45

Differentiate among the different types of mass movement based on the speed and the manner of movement.

Question 46

What is solifluction?

Question 47

Discuss how different slope compositions affect the likelihood of mass movement.

Question 48

How do lahars differ from other types of mass movements?

Question 49

Define the term "mass movement" and discuss the damages and deaths caused by mass- movement events in the United States.

Question 50

Which of the following could maintain the greatest angle of repose?

A) Dry sand.
B) Round creek pebbles.
C) Talus slopes containing large, highly angular boulders.
D) Wet sand.

Question 51

A fragile balance between driving and resisting forces can be upset by all of the following EXCEPT:

A) increase in slope angle by cutting the slope.
B) decrease the slope stability by shaking in an earthquake.
C) decrease in slope angle by grading the slope.
D) increase the weight on the slope by heavy rainfall.

Question 52

What forces encourage and oppose downslope movement?

Question 53

How does creep differ from other types of mass movements? What are the causes of creep?

Question 54

Describe the causes and types of mass movement found on the Moon and Mars.

Question 55

Could the La Conchita mudslide have been predicted?