Mass Movement

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  • Mass Movement
    • 'downslope movement of regloith by gravity'
    • Shear Strength
      • - the internal resistance of a body to movement
      • Factors contributing to reduce shear strength
        • Weathering effects
          • Disintegration of rocks;hydration of clay minerals;solution of minerals in rocks or soil
        • Changes in soil and ground-water pressure
          • Saturation, softening of material
        • Changes of structure
          • Creation of fissures in clays, removal of sands and clays
        • Biological effects
          • Burrowing of animals, growth and decay of roots
    • Shear Stress
      • - the force acting on a body that causes movement of the body down slope
      • Factors contributing to increased shear stress
        • Removal of suuport through undersutting or slope steepening
          • -e.g. erosion by rivers, glaciers, wave action, faulting, previous rockfalls or slides
        • Removal of underlying support
          • Undercutting by rivers waves, subsurface solutuion
        • Loading of slope
          • Weight of water, vegitation, accumulation of sediments
        • Lateral pressure
          • water in cracks, freezing in cracks, swelling, pressure release
        • Short term stresses
          • Earthquakess, movement of trees in wind
    • Types of mass movements
      • very slow movement (soil creep)
      • Fast movement (avalanches)
      • Dry movement (rockfalls)
      • Very fluid movements (mudflows)
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