AQA Specification Geography A.pdf

The Coastal Zone

  • Waves are usually formed by the wind blowing over the sea which creates friction, causing the water the form ripples. The stretch over which the wind blows is called the Fetch. The longer the fetch, the more powerful the waves.
  • Waves are caused by earthquakes and volcanoes as well, which can cause Tsunamis.
    • For Example, in December 2004, an earthquake triggered a Tsunami in the Indian Ocean.
  • There is little forward motion of water in waves, only when waves approach the shore, do they gain forward momentum.
  • This happens because the seabed intercepts the circular orbital movement of the water. The water then rushes up the beach as the friction of the seabed, distorts the motion and forces it upwards.

Water that rushes up the beach is the swash. The water flowing back is called the backwash.

Constructive Waves

  • these have a powerful swash
  • large amounts of sediment are deposited and they construct the beach (this is called deposition)
  • little erosion takes place however as they have a weak backwash
  • they are good for surfing and are usually formed by distant storms

Deposition

  • Coasts are built up when the amount of deposition is greater than the amount of erosion.
  • The amount of material deposited on an area increases when there is lots of erosion elsewhere on the coast.

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