Different Types of Glacier and Glacier Movement

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a) Formation of glacier ice

Snow

  • Flakes with open, feathery structure
  • Low density (0.05 g/cm^3)

Firn/Neve

  • Snow that survives a summer/whole year
  • Compressed and compacted by the fresh snow fall
  • Air expelled
  • Density is 0.4 g/cm^3

Glacier Ice

  • Further Compaction
  • Diagenesis- process by which snow becomes ice due to compression. Takes as little as 30-40 years up to over 1000 years
  • Density is 0.3 to 9.1 g/cm^3
  • Not found until depth of 100m
  • Blueish in colour
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b) Valley glaciers and ice sheets

  • Glacier- Large, slow moving mass of ice
  • Ice Sheet- Largest Accumulation of ice (>50,000km^2 (Otherwise called an ice cap))
  • There are only 2 ice sheers today (Greenland and Antarctica)
  • Antarctica- 13.6 million km^2, 30 million km^3, over 4700m deep in eastern antarctica

Valley Glacier

  • Confined by Valley Sides
  •             EITHER outlet glacier from ice sheet/cap OR fed by snow and ice from one or more corrie glaciers
  • Follow course of existing river valleys or corridors of lowland
  • Typically 10-30km long- Karakoram Mountains glacier in Pakistan up to 60km
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c) Warm based and cold based glaciers

Basal Temperature

  • Temperature at the base of the glacier where the ice meets the ground

Pressure Melting Point (PMP)

  • Temperature at which ice is on the verge of melting
  • At the surface it is 0°C
  • Further down is lower due to pressure

Temperature (Warm Based) Glaciers

  • Water at the surface in summer- may end up at base via fluvio-glacial system.

Polar (Cold Based) Glaciers

  • Temperatures at surface too cold for water to exist at any point of the year
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c) Warm based and cold based glaciers

Warm Based Glaciers

  • High altitude locations
  • Steep Relief
  • Basal Temperature at or above PMP
  •            Water at base of glacier between ice and ground
  •            Rapid movement rates
  •            20 to 200m per year
  • Significant amount of glacial erosion
  • Maximum impact on landscape

Cold Based Glaciers

  • High latitude locations
  • Low Relief
  • Basal temperatures below PMP
  • Ice frozen to bedrock
  • Very slow movement rates
  • Few metres per year or less
  • Limited movement or erosion
  • Limited landscape impact
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d) Glacial Movement

  • Gravity leads to glacial ice movements
  • Gradient- Steeper Gradient = faster movement
  • Thickness of ice affects basal temperatures and PMPs
  • Internal Temperatures of the ice- variations can allow movement of one area of ice relative to another
  • Glacial Budget- positive budget causes glacial advance
  • Nature and location of ice in the glacier can also affect movement
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