Attrition
The rock fragments during their to and for movement along with the prevalent waves and currents, collide with one another and are themselves worn down, as a result the fragments are reduced in size and facilitates easy transportation.
Corrosion
This is the solvent action of sea water. This is of relatively minor importance since the sea water has high salt content and calcium carbonate.
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The chemical action of the sea water is, however, seen where coasts are composed of readily soluble rocks such as limestone, dolomite etc.
Features Formed By Marine Erosion
Erosional processes by seas produce coastal cliffs, wave-cut benches etc.
(i) Cliffs
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As we know, steep shores suffer more destruction. Cliffs are steep wall like features carved in to a bedrock mass by a combination of marine undercutting and subaerial processes.
These are most important especially on coasts facing the full force of major storm waves. Because of the abrasion taking place actively at the base of the cliff, its upper part is undermined and crumbles and the cliff gradually recedes with a steep face towards the advancing sea.
Intense wave erosion causes the formation of a notch at the base of some cliffs. These are known as ‘wave-cut notch’ which mark the initial stages of under-cutting that leads to a mass movement as the cliff breaks away above the notch and falls into the sea.
Other minor erosional features associated with cliffs are the stacks, sea caves and sea arches. These are the isolated remnants of former land, produced as a part of the cliff retreat along lines of weakness in the rocks.
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These may be due to the differences in the strength of the rock, and structure of the rocks exposed.
When the rocks exposed in the cliff are composed of stratified sediments of varying strength, the weaker units are under cut rapidly forming sea caves and arches, which have resistant capping layers.
When an arch collapses, columnar masses or rock remain standing isolated as islands just off the shore. These columnar rock masses are called stacks.
These are temporary features which are ultimately leveled and are of minor relevance to the overall development of a coast.
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(ii) Wavecut bench
It is known variously as abrasion platform, shore platform, marine terraces etc. With continuous abrasion the rocks that have been dislodged from the cliff get dumped at the cliff foot, which is a gently seaward sloping seafloor, called the wave-cut bench. This sloping rock floor, with continued abrasion grows wider in the landward direction.