EROSION, TRANSPORTATION AND DEPOSITION.

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  • EROSION, TRANSPORTATION AND DEPOSITION.
    • EROSION
      • Vertical and lateral erosion change the cross profile of a river
        • Can be vertical or lateral- both happen at the same time.
          • One is usually dominant over the other at different parts of the river.
        • VERTICAL EROSION.
          • depends on the river valley and channel, making it V-shaped.
          • its dominant in the upper course of the river
        • LATERAL EROSION.
          • widens the river valley and channel.
          • dominant in the middle and lower course
      • HYDRAULIC ACTION: force of the water breaks down rock particles away from the river channel
      • ABRASION
        • eroded rocks picked up by the river scrape and rub against the channel, wearing it away.
        • most erosion happens by abrasion
      • ATTRITION
        • eroded rocks picked up by the river smash into each other and break into smaller fragments
        • their edges get rounded off as they rub together
      • SOLUTION: river water dissolves some types of rock; e.g. chalk and limestone
    • TRANSPORTATION
      • The material a river has eroded is transported downstream
      • 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 water
      • SUSPENSION: small particles like silt and clay are carried along by the water
      • SOLUTION: soluble materials dissolve in the water and are carried along.
    • DEPOSITION
      • happens when a river slows down (loses velocity)
      • when a river drops the eroded material its transporting
      • reasons why rivers slow down and deposit material:
        • volume of water in the river falls
        • river reaches its mouth
        • water is shallower, e.g. on the inside of a bend
        • amount of eroded material in the water increases

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