Coastal Processes: Erosion

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fileycliffs2_sm.jpgThe distinctive landscape of a cliff coastline has been formed by action. Cracks develop along weak points and caves begin to develop at sea level. These grow in size and feventually either carve through the cliff or meet another cave formed on the other side of the headland to make an arch. In some caves a blow hole is formed where compressed air escapes to the cliff top through a gap in the cave's roof. chalk stacks1_sm.jpg
Erosion continues until the roof of the arch collapses to form a which eventually wears down to leave a stump. Further out to sea the remains of the former coastline are revealed as a platform.

A cliff can also collapse if there is more than one rock type present. If the rock is below a harder rock it wears away faster forming a wave cut notch and the overhanging cliff can collapse. Another example is where the weaker rock is and absorbs lots of water causing a movement which makes this rock slip downhill, a process known as .

perran_stack1_sm.jpgThe waves themselves act in different ways. There can be 1) corrosion where erosion takes place or 2) corrasion also known as where material that is carried in a wave wears away the rock or 3) attrition where the power of the waves caused rocks to break up. Another effect is caused by 4) action where air is first trapped in a wave, is then compressed and the extra air pressure pushes through weak points causes them to expand and eventually collapse.

bay1_sm.jpgEventually the cliff retreats inland and the land in front of the cliff is covered in pebbles or shingle or sand and shaped bays form in between the headlands.
The coasts of Britain are also noted for beaches which are the result of the land first being pushed down by the weight of an ice sheet, then flooded to form a new coast once the ice melted. This new coast was attacked by the sea but the land began to rise as the ice pressure was no longer present and these beaches were raised above sea level.
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Some valleys are still flooded and these either form in mountaineous areas where the glaciers carved quite straight paths or where the ice sheet didn't reach.