Coastal Erosion Features

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Coastal Erosion Features

Coastal erosion processes create a number of significant landforms. There are a number of factors which affect the rate of this erosion:

i) Rock Type - A more resistant rock, such as granite, will be eroded slowly, whilst a less resistant rock, such as clay or mud, can be eroded very quickly.

ii) Jointing / Faulting - The more faults and joints a rock has the more susceptible it is to erosion, both from coastal and sub-aerial processes.

iii) Coastal Rock Arrangement - A coastlinewith rocks that run parallel to the coast is called a concordant or "Pacific" coastline. One that has rocks running at right angles to the coast is calleda discordant or "Atlantic" coastline.

Coastal Erosion Features

iv) Rock Angle - The angle that the coastalrocks dip can also cause erosion to occur at different rates. Many rocks aroundthe coasts of Britain are sedimentary, meaning they are layered.

  • Rocks that dip towards the sea produce gently sloping cliffs that are often affected badly by mass movement processes.
  • Rocks that dip away from the sea produce an uneven, steep cliff face with many overhangs.
  • Rocks that are horizontally bedded produce a steep cliff with small overhangs.
  • Rocks with vertical beds will produce vertical cliffs if the layer closest to the sea is resistant.
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Headlands and Bays.

  • Formed on an Atlantic (discordant) coastline due to the softer rock being eroded quicker than the harder rock.
  • Beaches form in the bays where the soft rock has been eroded away.
  • Headlands of more resistant, hard rock are left behind.

Cliffs & Wave Cut Platforms

  • Cliffs are formed when destructive waves attack the bottom of the rock face between high and low water mark.
  • The area under attack is eroded using the major processes of coastal erosion.
  • Points of weakness, such as faults and joints are attacked most, and eventually a wave-cut notch is gouged out.
  • The rock above overhangs the notch, and as it is cut deeper into the rock, gravity causes the overhanging rock to collapse.
  • The loose rocks are removed by the sea and transported along the coast by long shore drift.
  • The whole process of undercutting the cliff begins again.
  • As the cliff is eroded backwards it leaves behind a wave-cut platform, at the level of the low water mark.
  • This platform is rarely eroded, as the waves energy is concentrated on eroding the area between the high and low water mark, and not the rock that is underneath them.
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Caves, Arches, Stacks and Stumps

  • Mainly seen on headlands.
  • Waves start by attacking the main points of weakness in the rock: the joints and faults.
  • A point of weakness is increased in size until it becomes a cave
  • The waves continue to attack the cave, which finally results in an arch being formed through the headland.
  • The arch is attacked both by coastal erosion and sub-aerial erosion and finally the roof of the arch falls into the sea.
  • This leaves behind a stack, which is then slowly eroded down to become a stump.
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