Meltwater, ice movement controlling factors and ice movement

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  • Ice Movement - 2 types
    • Basal sliding
      • Involves the movement of a large block of ice - usually in a series of short jerks
      • It occurs in warm glaciers, where meltwater is present to help libricate the base of the ice
    • Internal deformation
      • Involves ice crystals slipping & sliding over each other
      • The ice crystals may become deformed or fractured & gradually move downhill in response to gravity
      • Occurs in both cold and warm glaciers - often at the same time as basal sliding
  • Meltwater
    • Forms on the upslope side of obstacles on the valley floor
    • Meltwater enables the ice to flow up and over the obstacle, although it often refreezes on the downslope side, where the pressure is reduced
  • Ice Movement Controlling Factors
    • Ice mass
      • The heavier the ice, the more potential energy it has to move
    • Steepness of the gradient
      • The steeper the gradient, the faster the ice will flow and the thinner the ice will become as its stretched out
        • Called extensional flow
        • The stretching often results in the ice cracking (crevasses)
      • A reduction in the gradient further down the glacier will slow the ice flow causing it to pile up and become thicker
        • Called expression flow
        • Here any crevasses will close
    • Meltwater
      • The presence of meltwater lubricates the base of the ice, allowing it to slip downhill
    • Gravity
      • The steeper the gradient, the greater the pull of gravity


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