Introduction to glaciers

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  • Created by: darcie_cl
  • Created on: 25-02-14 11:53
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  • Introduction to glaciers
      • Large bodies of ice that flow downhill in response to gravitational forces
      • Glaciers range in size from small valleys to vast ice sheets
      • Glaciers can be classified according to size and shape and by the glacial ice temperature
      • Niche - patches of snow and glacial ice in small hollows and gullies
      • Cirque - glacier that sits in a basin (bowl) feature
      • Valley - large streams of ice that glows within a valley from an up-slope cirque or ice cap
      • Piedmont - large blobs of spreading ice when valley glaciers expand onto flat land
      • Ice cap - done shaped mass of glacial ice that peaks over mountains
      • Ice sheets - masses of ice that covers an entire landscape
      • Ice shelves - floating ice where glaciers extend out to sea
      • Polar or Cold based
        • In very cold environments glaciers are frozen into the bedrock beneath and melting only occurs at the surface during the short summer season
      • Temperate or warm based
        • In mild summer temperatures melting occurs at the base of the glaciers as temperatures are close to the pressure melting point
      • Polythermal
        • Glaciers contain both cold and warm ice
      • Primary source of ice in a glacier is snowfall
      • The transformation of snow into ice is a complex sequence of compression, partial melting and refreezing
      • Step 1 - the thick snow base (5-10m) is compressed by the weight of the overlying snow into a mass of granular ice crystals = firn
      • Step 2 ; summer meltwater from the snow above percolates down into firn and refreezes
      • Step 3; the weight of overlying ice squeezes any remaining air bubbles out
      • Cross - section through a glacier = bedrock, glacial ice, firn, granular ice (50% air), freshly fallen snow
      • Latitude - must be north or south
      • Altitude - height
      • Aspent - way the glacier is facing
      • Contientality - extent/thickness of temperature and precipitation
      • Topography - shape of land


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