Friday, 25 December 2015

Marine Agents of Erosion

1) Corrasion :- Waves armed with rock debris of all sizes and shapes charge against the base of the cliffs, and wear them back by corrasion. On-coming currents and tides complete the work by sweeping the eroded material into the sea.

2) Attrition:- The constantly moving waves that transport reach materials such as boulders, pebbles, shingle and fine sand also hurl these fragments against one another, until they are broken down by attrition into very small pieces. The grinding and polishing of such fragmental materials against cliff faces and against each other is largely responsible for the fine sand which forms the beaches that are so typical of the seaside resorts.

3) Hydraulic action :- In their forward surge, waves splashing against the coast may enter joints and crevices in the rocks. The air imprisoned inside is immediately compressed. When the waves retreat, the compressed air expands with explosive violence. Such action repeated again and again soon enlarges the cracks and rock fragments are prised apart.

4) Solvent action :- On limestone coasts, the solvent action of sea water on calcium carbonate sets up chemical changes in the rocks and disintegration takes place. This process is limited to limestone coasts.

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