Cold Environments Basics

Global distribution
1. Glacial environments
  1. areas covered by ice sheets and glaciers
  2. Antarctica or Greenland
2. Periglacial (Tundra) Environments
  1. North Alaska & Canada
  2. exist in dry high-latitude areas not permanently covered in snow and ice
3. Alpine regions
  1. Himalayas and the Alps
  2. May contain small ice caps, mountain glaciers and tundra environments
Ice formation and movement
1. The snowline
  1. The line between the areas of permanent snow and areas where snow melts
2. Firn
  1. when snow is compressed
    1. between being snow and ice
  2. Sometimes known as neve
    1. Will eventually become ice
3. Two types of Glacier
  1. Temperate (alpine) Glaciers
    1. melt in the summer
      1. release huge amounts of meltwater
        acts as a lubricant reducing friction
    2. Move by basal flow, extending/ compressing flow, creep and surges
    3. more likely to erode, transport and deposit material
  2. Polar Glaciers
    1. occur where the temp is always below 0 degrees C
      1. no melting occurs
    2. Movement is slower as the glaciers are frozen to their beds
      1. They move mainly by internal flow
      2. Much less erosion, transportation and deposition occurs
  3. How ice moves down a hill
    1. Upper Zone
      1. ice is brittle, breaking apart to form crevasses
    2. Lower Zone
      1. has a steady pressure
      2. meltwater from the pressure and friction allows a more rapid, plastic flow
        at depth in the glacier the melting point of the ice is raised slightly by the increased pressure
        Basal ice is therefore more likely to melt at temperatures close to 0 degrees C
4. How ice moves
  1. Compressing Flow
    1. when there is a reduction in the gradient of the valley floor
      1. Ice decelerates
        a thickening of ice mass
      2. erosion is at its max
  2. Extending Flow
    1. when the valley floor becomes steeper
      1. ice acceleration and becoming thinner leads to less erosion
  3. Basal Flow
    1. Friction as moves over bedrock
      1. melting at bottom
        acts as a lubricant
        can flow more rapidly
  4. Surges
    1. occur when there is an excessive build-up of meltwater under glacier
      1. 250-300m in one day
      2. presents hazards for those living in the valley below the snout
  5. Internal Flow
    1. when ice crystals orientate themselves in the direction of the glacier's movement and slide past each other
      1. as surface ice moves faster, crevasses develop
    2. the main way polar glaciers move as no need for meltwater
  6. Creep
    1. occurs when stress builds up in the glacier
      1. allows ice to behave with plasticity and flow
      2. It occurs particularly when obstacles are met
  7. Rotational Flow
    1. Occurs within a corrie
      1. ice moving downhill pivots about a point
        this produces rotational movement
        increased pressure within the rock hollow, leads to greater erosion and an over deepening of the corrie floor

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Cold Environments Basics

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