Chapter 15 – Mass Wasting – Flashcards
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Define mass wasting.
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The downslope movement of sediment and rock under the direct influence of gravity.
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A __________ is formed when vertical incision by a stream is the primary process, with relatively minimal mass wasting.
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slot canyon
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Which of the following correctly states the role of rivers and mass wasting in the formation of the Grand Canyon?
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The Colorado River erodes downward, then mass-wasting processes move material from high to low areas, then the Colorado River transports material downstream.
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Over time, mass wasting causes __________.
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canyons to widen
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What rock type is the easiest for a river to cut through?
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shale
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The Gros Ventre slide is evident today by __________.
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a scar, runout area, and landslide debris filling the valley
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Which of the following is a reason the Gros Ventre rockslide took place?
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Because the river eroded material at the valley base, there was no support of the material upslope.
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A __________ acted as a sliding surface across which material moved downhill during the Gros Ventre Slide.
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clay layer
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Heavy rainfall caused the clay to lubricate and the sandstone to become __________.
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saturated and heavy
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Which of the following statements is true regarding the aftermath of the Gros Ventre rockslide?
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The rockslide debris dammed up the river and formed a lake.
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Creep is __________.
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mass wasting by the gradual downhill movement of sediment, influenced by freeze-thaw or wet-dry cycles
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Describe how a soil particle moves downhill during the freeze-thaw process.
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During the freeze, a soil particle moves at a right angle away from the surface, and thawing causes the particle to fall back to a slightly lower level.
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Why would trees be J-shaped?
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The trunks become tilted in the downhill direction due to creep, but continue to grow toward the sun.
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Which of the following is associated with creep?
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slow and subtle movement of material
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A __________ is a common result of creep.
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broken retaining wall
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Permafrost is __________.
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permanently frozen ground of tundra and subarctic climates that has remained 0°C for two years or more
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__________ is an example of mass wasting commonly seen in the active layer above permafrost.
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Solifluction
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What is name of the near-surface layer that thaws in the summer?
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the active layer
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If permafrost is melted, which of the following is a consequence?
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The ground subsides because the volume of water is less than that of ice.
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What is used to keep the Trans-Alaska pipeline from melting permafrost?
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stilts
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Mass wasting is possible only with the aid of a transportation agent such as water, wind, or ice.
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False
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What non-geologic term is commonly used to describe a sudden event in which large volumes of material move down steep slopes?
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Landslide
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What is the angle of repose?
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The steepest angle at which a material remains at rest
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The 2005 mass-wasting event in La Conchita, CA, can be classified as a ______.
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debris flow
