Chapter 16 (GEOL107)

Identify the true statement. Choose one: A. Weathering does not affect the stability of a slope. B. Vegetation is heavy, and therefore deforesting an area can help keep slopes stable. C. Forest fires followed by heavy rains are likely to result in severe mud and debris flows. D. Saturating a slope with water tends to hold unconsolidated grains together and thus helps stabilize slopes.

C. Forest fires followed by heavy rains are likely to result in severe mud and debris flows.

Where did the following mass-wasting event take place? A layer of rock broke loose along an exfoliation joint and caused damage in a famous recreation area. Choose one: A. Elm, the Swiss Alps (1881) B. Armero, Colombia (1985) C. Yosemite National Park (1996) D. Gros Ventre Slide, Wyoming (1925)

C. Yosemite National Park (1996)

Where did the following mass-wasting event take place? Quarrying undercut a 600-m-high cliff and triggered a rockfall of over 10 million cubic meters that buried a nearby town and its inhabitants to a depth of 10 to 20 m. Choose one: A. Elm, the Swiss Alps (1881) B. Armero, Colombia (1985) C. Yosemite National Park (1996) D. Gros Ventre Slide, Wyoming (1925)

A. Elm, the Swiss Alps (1881)

Where did the following mass-wasting event take place? A river eroded away the base of the mountain slope it flowed alongside, causing a huge landslide that filled the valley and dammed its flow. Choose one: A. Gros Ventre Slide, Wyoming (1925) B. Armero, Colombia (1985) C. Elm, the Swiss Alps (1881) D. Yosemite National Park (1996)

A. Gros Ventre Slide, Wyoming (1925)

Identify the statement that is true about mass movement. Choose one: A. It becomes possible when strong, intact rock gets weathered. B. Mass-movement zones are difficult to predict. C. It happens when joints and faults are oriented perpendicular to slopes. D. It occurs when downslope force equals resistance force.

A. It becomes possible when strong, intact rock gets weathered.

Mass movement Choose one: A. is a gravity-driven downslope movement of natural materials. B. happens only when the slope of a hill gets steeper than the angle of repose. C. can't happen underwater because the buoyancy force of water is too great. D. is more likely to happen under dry conditions than under wet conditions.

A. is a gravity-driven downslope movement of natural materials.

Which of the following increases the chances of a mass movement? Choose one: A. raising the water level behind a dam to hold down a potential failure surface B. adding subsurface drainage to reduce water content on a slope C. redistributing the mass on a slope by terracing D. planting vegetation on newly graded slopes

A. raising the water level behind a dam to hold down a potential failure surface

Solifluction Choose one: A. means that the level of the water table fluctuates with precipitation. B. is a kind of creep that is found in high-elevation regions or in the Arctic on slopes that are underlain by permafrost. C. is the proper term for alternate expanding and contracting of swelling clays. D. is a faster-than-usual kind of slump in wetlands.

B. is a kind of creep that is found in high-elevation regions or in the Arctic on slopes that are underlain by permafrost.

The Vaiont Dam area was vulnerable to mass movement because Choose one: A. underlying granite bedrock had begun to weather. B. limestone beds there dipped parallel to the mountain slope and were interlayered with weak shale. C. logging in the region had stripped the mountain tops of vegetation. D. shale layers in that region dipped into the mountain slope, causing weakness.

B. limestone beds there dipped parallel to the mountain slope and were interlayered with weak shale.

Landslides are likely to happen when Choose one: A. weight is added at the bottom of a slope. B. the downslope force becomes greater than the resistance force. C. the angle of repose of a sandy slope becomes greater than 9°. D. weak surfaces dip into the slope.

B. the downslope force becomes greater than the resistance force.

Which of the following would increase the risk of having a landslide? Choose one: A. adding support to the toe of the slope B. removing weight at the top of the slope C. allowing water to infiltrate the slope D. recontouring the slope to reduce its slope angle

C. allowing water to infiltrate the slope

Avalanches Choose one: A. never happen twice in the same place; therefore, the pathway an avalanche creates is a safe place to build. B. always contain snow and/or ice. C. can be triggered by explosions, people, or even just new snow. D. are slow mass-movement events.

C. can be triggered by explosions, people, or even just new snow.

The Vaiont Dam disaster Choose one: A. occurred in the early 1800s before engineers understood how to build safe dams. B. was the worst dam disaster in the United States. C. happened because a properly engineered dam was built in a geologically unstable location. D. came as a total surprise, with no warning signs.

C. happened because a properly engineered dam was built in a geologically unstable location.

The tragedy in 1970 at Yungay, Peru, Choose one: A. was surprising because there was no evidence of previous landslides there. B. could happen again, unfortunately; the government rebuilt the town in the same place. C. started with an earthquake that triggered an icefall that triggered a debris flow. D. is not considered mass wasting, because it happened quickly and, by definition, mass wasting is slow movement of material downslope.

C. started with an earthquake that triggered an icefall that triggered a debris flow.

Where did the following mass-wasting event take place? A lahar in the Andes buried this town and its inhabitants. Choose one: A. Elm, the Swiss Alps (1881) B. Yosemite National Park (1996) C. Gros Ventre Slide, Wyoming (1925) D. Armero, Colombia (1985)

D. Armero, Colombia (1985)

Identify the true statement. Choose one: A. Lahars are mudflows that have been triggered by earthquake shaking. B. Slow movement of unconsolidated material downslope is called a turbidity current. C. The head scarp of a slump is found at the base of the slump block. D. The angle of repose is the steepest angle at which unconsolidated sediments can sit without slipping downhill.

D. The angle of repose is the steepest angle at which unconsolidated sediments can sit without slipping downhill.

Quick clay Choose one: A. behaves like a liquid when still. B. is an example of solifluction. C. isn't clay at all, but a deposit of sand that moves downslope. D. can move like a liquid when vibration or shaking separates the water-coated particles.

D. can move like a liquid when vibration or shaking separates the water-coated particles.

Which of the following processes most logically explains the different tilts of gravestones in a hillside cemetery? Choose one: A. mudflow B. slump C. liquefaction D. creep

D. creep

Slides with a spoon-shaped (concave-up) surface are called Choose one: A. avalanches. B. debris flows. C. creep. D. slumps.

D. slumps.

Which of the following is a suitable method of managing snow avalanches? Choose one: A. increasing the slope's load by planting vegetation on the cornice of mountain slopes B. expansive water drainage systems C. allowing skiers to use only avalanche chutes (regions where avalanches will not occur) D. targeted, controlled explosions

D. targeted, controlled explosions

Classification of mass-movement events is based on Choose one: A. the slope angle (greater than or less than 30˚) B. the amount of turbulence (low, medium, or high levels). C. the age of the material involved (historic, thousands of years old, or millions of years old). D. the type of material involved (rock, regolith, snow, and ice).

D. the type of material involved (rock, regolith, snow, and ice).