Rivers

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  • Created by: vampette
  • Created on: 12-04-14 08:37
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  • Rivers
    • Long profile of a river
      • Upper course
        • Steep gradient
          • V-shaped valley, steep sides, narrow, shallow channel
      • Middle course
        • Medium gradient
          • Gently sloping valley sides, wider deeper channel
      • Lower course
        • Gently gradient
          • Very wide, almost flat valley, very wide, deep channel.
    • Erosion can be vertical or lateral- both types happen at the same time but one is more dominant at different point along the river
      • Vertical eroion
        • This deepens the river valley (and channel), making it V-shaped. it's dominant in the upper course of the river
      • Lateral erosion
        • This widens the river valley (and channel). It's dominant in the middle and lower course.
    • There are four processes of erosion
      • Hydraulic action
        • the force of the water breaks rock particle away from the river channel
      • Abrasion
        • Eroded rocks picked up by the river scrape and rub against the channel, wearing it away.
      • Attrition
        • Eroded rocks picked up by the river smash into each other and break into smaller fragments. Their edges also get rounded off as they rub together.
      • Solution
        • River water dissolves some types of rock, e.g. chalk and limestone
    • Transportation is the movement of eroded material
      • Traction
        • Large particles like boulders are pushed along the river bed by the force of the water
      • Saltation
        • Pebble-sized particles are bounced along the river bed by the force of the water
      • Suspension
        • Small particles like silt and clay are carried along by the water
      • Solution
        • Soluble material are dissolved in the water and carried along.
    • Deposition is when a river drops eroded material
      • It happens when a river slows down (loses velocity)
        • reasons why a river loses velocity and deposits material:
          • The water is shallower, e.g. on the inside of a bend
          • The amount of eroded material in the water increases
          • The river reaches its mouth
          • The volume of water in the river falls

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