Glaciation 1.2.5 - Erosion

  • Created by: BluJay117
  • Created on: 02-10-18 14:50
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  • Erosion
    • Abrasion
      • Ice at the bottom of the glacier carries debris with it and this, in turn, abrades the bedrock surface
      • The amount and rate of glacial abrasion is determined by a number of factors, including:  Ice thickness  Speed of glacier movement  Sub-glacial  meltwater      Debris supply, shape and relative hardness
      • Abrasion is evident in the formation of glacial striations or  striae  (scratches on bedrock)
      • The grinding down of the bedrock and debris as the ice moves produces a fine powder known as glacial flour
    • Plucking
      • Also known as joint block removal
      • Plucking requires the bedrock to be jointed and therefore weakened
      • Ice freezes onto the bedrock and then blocks of bedrock become incorporated into the sole of the glacier
      • Melting (pressure melting point) and refreezing need to occur and this is most likely to happen where there is an obstacle obstructing the flow path of the glacier.  The process of regelation occurs
    • Sub-Glacial Fluvial Erosion
      • works through both mechanical and chemical means, and increases in importance toward the snout of a glacier where there is most  meltwater
      • Fluvial abrasion occurs where   meltwater  flows across the bedrock surface under pressure.  This is the process by which particles carried in the flow abrade the bedrock, causing scouring and grooving
      • particularly effective if the meltwater is carrying a relatively coarse load of suspended sediment
      • also influenced by meltwater flow velocity and by the roughness and irregularity of the channel
      • Where meltwater flow accelerates around obstacles, for example, vapour bubbles can form: these eventually collapse causing shock waves that can be very effective in opening up microscopic cracks in the rock and loosening mineral grains
      • Depending on the type of bedrock, glacial meltwater can also cause erosion through dissolving minerals and carrying away the solutes

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