erosion process

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  • geography revision resourses
    • erosion process
      • Hydraulic  action
        • Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.
      • Abrasion
        • Bits of rock and sand in waves grind down cliff surfaces like sandpaper.
      • Attrition
        • Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.
      • corrosion/ solution
        • Acids contained in sea water will dissolve some types of rock such as chalk or limestone.
      • Acids contained in sea water will dissolve some types of rock such as chalk or limestone.
    • transport process
      • traction
        • Pebbles and larger sediment are rolled along the sea bed.
    • characteristics of a river
      • upper course
        • steep valleys, narrow/ shallow river channels, high bed load (pebbles and rocks)
      • middle course
        • open/ gentle sloping, valley with floodplains with more suspended sediment
    • formation of a meander
      • meander is a bend in the river. water is always faster on the outside of the bend.
      • Water twists and turns around stones and other obstructions resulting in areas of slower and faster water movement. Slower areas are found in deeper parts of the river filled with fine sediments and are called pools. Faster areas are found in shallower parts of the river around larger stones and are called riffles.
        • The river starts to flow from side to side in a winding course but still in a relatively straight channel. The pools tend to move to opposite sides of the channel over time and this is where a meander  will develop. Water moving faster has more energy to erode. This occurs on the outside of the pool.
  • saltation
    • Load is bounced along the sea bed, eg small pieces of shingle or large sand grains. Currents cannot keep the larger and heavier sediment afloat for long periods.
    • transport process
      • traction
        • Pebbles and larger sediment are rolled along the sea bed.
  • suspension
    • Small particles are carried in water, eg silts and clays, which can make the water look cloudy. Currents pick up large amounts of sediment in suspension during a storm, when strong winds generate high energy waves.
    • Minerals are dissolved in sea water and carried in solution. The load is not visible. Load can come from cliffs made from chalk or limestone, and calcium carbonate is carried along in solution.
      • solution
      • lower course
        • open/ gentle sloping valley with flood plains, flat and wide floodplains, and very wide and deep channels
        • characteristics of a river
          • upper course
            • steep valleys, narrow/ shallow river channels, high bed load (pebbles and rocks)
          • middle course
            • open/ gentle sloping, valley with floodplains with more suspended sediment

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