Coastal erosional processes

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Coastal erosional processes


When waves approach the coastline they are carrying material such as sand, shingle, pebbles and boulders. Abrasion occurs when this material is hurled against cliffs as waves hit them, wearing the cliff away.

Hydraulic pressure:

Cliffs and rocks contain many lines of weakness in the form of joints and cracks. A parcel of air can become trapped/compressed in these cracks when water is thrown against it. The increase in pressure leads to a weakening/cracking of the rock.


Seawater contains carbonic acid, which is capable of dissolving limestone. The evaporation of salts in seawater produces crystals and their formation can lead to the disintegration of rocks.


Coastal erosional processes that are not linked to the action of the sea. Erosion occurs via rain, weathering by wind and frost. Its impact is often seen in soil creep, slumping and landslides.

Human activity:

Much building and recreation occurs at the coast, and this increases pressure on cliff tops, making them more liable to erosion and subsidence. The building of sea defences upsets the dynamic equilibrium of the coastline.

The rate at which a stretch of coastline is eroded is related to the following factors:

  1. The point at which the wave breaks - (if at the foot of a cliff, the cliff is subject to maximum energy and most erosion).
  2. Steepness of the wave.
  3. Depth of sea, fetch, aspect.
  4. Amount of beach material - (a wide beach protects a cliff more than an arrow beach).
  5. Rock type and structure - (hard rock such as granite is far more resistant to erosion than soft rocks, such as clay).