1. Marine Erosion Processes
VV ‘05

2. Hydraulic Action
The force of waves hitting a cliff (or sea wall) compresses water and air into cracks and joints. This can be equivalent to 30,000kg per square metre.
This increase in pressure may lead to cracks widening and pieces of rock breaking off.

3. Corrasion (abrasion)
Rock fragments may be picked up by waves and thrown against the rock face of cliffs by subsequent waves.
The effectiveness of the corrasion depends on the strength of the wave, the nature of its ‘load’ and the resistance of the rock in the cliff face.
Corrasion is most effective at the base of cliffs

4. Attrition
Rock fragments which have become detached by hydraulic action and corrasion are worn down into smaller and more rounded pieces.
Currents and tidal movements cause the fragments to be swirled around and to grind against each other.
This type of erosion produces pebble beaches.

5. Corrosion (solution)
Salts and acids in sea water can react with rocks , slowly dissolving them away.
The photo shows this process on a cliff of Portland limestone which has been chemically attacked by carbonic acid and other chemicals in sea water.

6. Rates of erosion depend on many factors:
Waves – strength, frequency, height
Weather – frequency of storm conditions
Geology of the coastline :
type of rock
degree of resistance
stratification
stability