Geology: Mass Wasting

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  1. Define mass wasting and note its importance in landform development.
    Downslope movement of earth materials due to gravity
  2. Define Erosion.
    Incorporation and transportation of material by a mobile agent (e.g. wind, water, ice)
  3. Define Weathering.
    Disintegration or decomposition of rock near the surface of the earth
  4. Identify and describe the triggers for mass wasting.
    Water - diminishes particle cohesion (friction) and adds weight

    Oversteeping of slope - angle of repose (maximum angle at which rock and soil remain stationary without sliding(different for different meterials)

    Removing of anchoring vegetation (trees and plant absorb water. Removing them floods the surface with muddy water.)

  5. What three criteria do we use to classify types of mass wasting?
    • Fall - free fall of pieces
    • Slide - material moves along a surface (e.g. joint, fault, bedding plane, curved surfaces)
    • Flow - material moves as a viscous liquid
  6. What is a slump and what is unique about it?
    • Movement of a mass of rock or unconsolidated material as a unit along a curved surface.
    • Occurs often along steeped slopes
  7. How are talus slopes formed?
    When rocks break off of a cliff face or mountain.  The rocks tumble down the slope, coming to rest in a large pile of "talus."
  8. What is the difference between debris flow and earthflow?
    Debris flows are wet and fast while Earth flows are slow and dry.
  9. What is creep?
    Gradual movement of soil and regolith downhill
  10. What is Solifluction?
    The slow, downhill movement of soil down a steep slope

    Promoted by a dense clay hardpan or impermeable bedrock layer

    Can occur on gentle slopes
  11. What is the force that causes mass wasting?
  12. What force resists mass wasting?
  13. Describe the significance of the angle of repose.
    It causes oversteeping
  14. Explain why building a house on an alluvial fan might not be a good idea.
  15. Identify areas at risk of lahars.
    Areas of volcanism
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Geology: Mass Wasting
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