week 12 mass wasting glaciers

week 12 mass wasting glaciers - Mass wastings...

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Mass wastings “Landslide Hazards: A National Issue”    USGS -  Landslides constitute a major  geologic hazard because they are  widespread,  - Occur in all 50 states and U.S.  territories, - Cause $1-2 billion in damages  and > 25 fatalities on average each  year.  Landslides.usgs.gov
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Mass Wasting Movement of rock, regolith or soil under gravity - distinct from other erosional processes - does not require transport medium - may be imperceptibly slow or a thunderous landslide Worldwide “landslides” cause 600 deaths per year   extreme individual events can claim thousands Gravity  main driver, but also important: water : pores get filled with water and cohesion reduced Oversteepened slopes: angle of repose   exceeding angle causes failure also occurs in cohesive slopes (bedrock, cohesive soils) - e.g. coastal bluffs, river undercutting
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Vegetation -Binds slope material and reduces pore water reducing risk of mass wasting - removing vegetation can cause hazard Earthquakes -Often trigger mass movements - often mass movements cause more damage than damage from shaking
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DEFINITIONS: • Fall Movement without contact with other surfaces during event    • Slide Movement along a definable contact plane with no or little internal disruption • Flow Movement involving considerable internal deformation with no obvious contact plane      (Rheology: viscous)   Slide: No internal disruption (fortunately)
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Occurs on land   Source:  Roger J. Wyan/AP Wide World Photo
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Can be submarine
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Fall   June, 1999, Glacier Point June, 1996,  Happy Isles Yosemite National Park
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Rotational slide,  slumping planar,  along slip planes within the slope,  SLIDE Translational slide A B
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week 12 mass wasting glaciers - Mass wastings...

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