AQA AS Geography Coasts: Mindmap 2

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  • Physical geography
    • Factors that determine the energy of a wave
      • Strength of the wind (controlled by the pressure gradient)
        • Wind moves from areas of high pressure to low pressure. The greater the difference in pressure, the faster the wind.
      • Duration of the wind
      • The fetch
    • Tides and currents
      • Rip currents: occur on some beaches and are strong, localised underwater currents. They normally form when a series of plunging waves causes a build up of water at the top of the beach.
      • Tides: tides are changes in the water level due to gravitational pull from the moon.
    • Formation of waves
      • Wind blows over the surface of the water, creating tiny ripples.
        • Circular motion of the water particles begins.
          • Closer to the coast, the water becomes shallower and the water particles' circular orbit elongates, becoming elliptical.
            • The wavelength and velocity then decreases due to friction along the seabed, increasing wave height.
    • Low energy and high energy coastline characteristics
        • Rocky coatline
        • streches of the atlantic facing coast wher wave are more powerful eg. Cornwall
        • Where erosion occurs mire than deposition
        • Lots of erosional landforms eg. headlands
      • LOW ENERGY
        • Sandy coastline
        • sheltered from large waves eg. bays of lincolnshire
        • Where deposition occurs more than eroison
        • Lots of depositional landforms eg. beaches and spits
    • Wave refraction
      • Wave refraction causes energy to be concentrated at headlands and dissipated at bays. This us why both erosional and depositional landforms form.
    • Sources of sediment
      • Rivers, glaciers, offshore, wind, cliff erosion, longshore drift
    • A sediment cell is a stretch of coastline, usually bordered by 2 prominent headlands, where the movement of sediment is more or less contained. A sediment cell contains...
      • Inputs
      • Outputs
      • Transfers
      • Sinks (stores)
      • Material in a sediment cell can be considered as a sediment budget with losses and gains. In principle, a state of dynamic equilibrium is attempted to be achieved through various gains and losses though this can be upset by events such as large river discharge.


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