Geography revsion

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  • Geography
    • Erosional Proesses
      • Hydraulic action: the force of the river against the banks cause air to be trapped in the cracks and crevices. making the bank weak and to wear away.
    • Meanders:In the middle course the river has more energy and a high volume of water. The gradient here is gentle and lateral (sideways) erosion has widened the river channel. The river channel has also deepened. A larger river channel means there is less friction, so the water flows faster:
      • As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders.
        • The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream
          • The force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy due to decreased friction
            • The inside of the bend,where the river flow is slower, material is deposited, as there is more friction.
  • Abrasion: rocks carried along by the river wear down the river bed and banks.
    • Hydraulic action: the force of the river against the banks cause air to be trapped in the cracks and crevices. making the bank weak and to wear away.
    • Attrition:rocks being carried by the river smash together and break into smaller, smoother and rounder particles.
      • Solution: soluble particles are dissolved into the river.
  • Formation of a waterfall
    • waterfalls often form in the upper stages of a river, where it flows over different bands of rock. it erodes soft rock more quickly than hard rock and this may lead to the creation of a waterfall.
      • The soft rock erodes more quickly, undercutting the hard rock
        • The hard rock is left overhanging and because it isn’t supported, it eventually collapses
          • The fallen rocks crash into the plunge pool. They swirl around, causing more erosion.
            • Over time, this process is repeated and the waterfall moves upstream
              • A steep-sided gorge is formed as the waterfall retreats

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