There are three main processes at work in the sea. These are erosion, transportation and deposition.
Erosion
Erosion is destructive waves wearing away the coast.
There are four main processes which cause coastal erosion. These are corrasion/abrasion, hydraulic action, attrition and corrosion/solution.
Corrasion/abrasion is when waves pick up beach material (e.g. pebbles) and hurl them at the base of a cliff.
When waves hit the base of a cliff air is compressed into cracks. When the wave retreats the air rushes out of the gap. Often this causes cliff material to break away. This process is known as hydraulic action.
Attrition is when waves cause rocks and pebbles to bump into each other and break up.
Corrosion/solution is when certain types of cliff erode as a result of weak acids in the sea.
You can view animations of each of these processes here (this will open in a new window/tab).
You can find out about the landforms created as the result of coastal erosion here.
Transportation
Transportation is the movement of material in the sea and along the coast by waves. The movement of material along the coast is called longshore drift.
Longshore Drift
Longshore drift is the movement of material along the shore by wave action.
Longshore drift happens when waves moves towards the coast at an angle. The swash (waves moving up the beach) carries material up and along the beach. The backwash carries material back down the beach at right angles. This is the result of gravity. This process slowly moves material along the beach.
Longshore drift provides a link between erosion and deposition. Material in one place is eroded, transported then deposited elsewhere.
Transportation
Although longshore drift is the main process of transportation the material moves in four different ways. These are:
Traction - large material is rolled along the sea floor.
Saltation - beach material is bounced along the sea floor.
Suspension - beach material is suspended and carried by the waves. .
Solution - material is disolved and carried by the water.
Deposition
Deposition is when eroded material is dropped by constructive waves. It happens because wave have less energy. Deposition creates a range of landforms. You can find out more on the depositional landform geotopic.
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