Coasts

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Wave Refraction

1. When waves approach an irreegular coastline, they are refracted and become increasingly parralel to the coastline

2. The part of the wave that is still in deeper water moves faster causing the wave to bend around the headland. Wave energy becomes concentrated on the headland - causing greater erosion

3. The low energy part of the wave spills onto the beach causing deposition. As waves pile against the headland, there may be a slight rise in sea level that results in long shore currents from the headland, moving some of the eroded material towards the bay, contributing to beach build up.

  • Parralel
  • Bend around the headland
  • Beach depoisition
  • Rise in sea level
  • Longshore currents
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Formation of a Spit

  • Formed where the coast suddenly changes direction i.e. across a river mouth
  • Longshore drift continues to deposit material across the mouth of a river which results in the formation of a long bank of sand and shingle forming
  • Changes to the dominent wind and waves may lead to the spit having a recurved end
  • Area behind the spit is sheltered from the waves - salt marsh
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Sea level rise

Isostatic change = Local changes in sea levels due to the rise and fall in land masses where ice accumulates and its weight presses down on the crust causing land to sink lower into the mantle. 

Caused by isostatic uplift or tectonic uplift

Eustatic change = Global changes in sea level rise due to variations in the amounts of water in the oceans

Caused by tectonic movements of the earths crust or changes in climate

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Landforms of Submergence

  • Land sinking or sea level increase

Rias

  • Submerged river valleys
  • The lowest part of the rivers course and the floodplains along the river may be completely drowned but higher land remains exposed
  • Valley curved out by ice - freeze thaw action in glaciers gauged valley out with it. Then sea levels rose and filled it up
  • Supplied by tributaries
  • Wide channel due to lateral erosion
  • Broad v-shaped valley
  • 40-50 metres deep
  • i.e. UK
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Coastline of Submergence

Fjords

  • Valley due to retreating ice
  • U-shaped
  • Fed by water falls
  • 300-400 metres deep
  • Straight profile
  • i.e Norway
  • Formed when descending glacier carves u-shaped valley into the bedrock
  • Have a threshold that occurs due to reduced glacial erosion as the glacier comes into contact with the sea and the sea became thinner, therefore eroding less.
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Landforms of Emergence

  • Sea level decrease, land rising
  • Sub-aerial weatherign and a lack of marine erosion means weathered debris collects at the foot of the cliff which over time produces gentle slopes e.g isle of Arran -8,15,30 metre beaches
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