Investigating

Coasts

A Website designed for Geography education in Primary Schools.

Coastal Processes

Coastlines are ever changing.This is because of the Sea. The sea is extremely powerful and has the ability to transport sediment and to erode beaches and cliffs. Erosion causes parts of the land to be lost, whereas Deposition causes parts of the land to be built up. There are three main coastal processes:

Changing Coastlines

Erosion is the eroding away of a substance, such as cliffs and beaches on the coastline. Erosion on the coast happens in a number of ways, but all are caused by the sea. Erosion may be caused by abrasion, where rocks are hurled at cliffs and the rocks wear the cliff away. Erosion of the coastline by these processes, causes the shaping of it and creates erosional features.

There are other methods of erosion on coasts, these are:

• attrition
• solution
• hydraulic action

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Transportation

This is the process where the sea moves coastal material, such as pebbles and sand particles. The sea has energy which allows it to pick up these materials and as the sea is always moving, it moves the material around also, until it deposits it when it loses some of its energy, for example when the waves move onto the beach.

The process of transportation causes the movement of beaches, known as Longshore Drift. This happens when the wind makes the waves move towards the coast at an angle. This washes material, which has been transported by the sea up the beach (swash) in that direction. As the waves come back down the beach (backwash) it moves straight down the beach, carrying the material with it. This happens along the coastline, with material moving along the beach in a zig-zag pattern.

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Longshore Drift

diagram courtesy of www.geography.learnontheinternet.co.uk

Deposition

This occurs where the sea loses some of its energy and moves more slowly, meaning it can no longer carry sediment. The sea deposits its load, some of this will be carried out to sea by the current but the rest will be deposited on the surrounding shoreline, by the waves. This process causes depositional features found on the coastline, such as beaches and spits. Deposition can have positive and negative effects on the coastline, the formation of beaches is a positive effect because they protect the cliffs and attract tourists. Sometimes deposition can silt up harbours and this causes danger for ships, so this is a negative effect.

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