HYDRAULIC ACTION Power of the water breaks fragments off cliffs because air is compressed into cracks by incomming waves but when the waves move away the air expands explosively weakening the rock.
CORROSION The chemical reaction between certian rock types such as chalk and limestone and the salt and acids in seawater which breaks down the cliff.
CORRASION sand and pebbles carried in water are thrown against the cliff by the breaking wave, wearing it away.
BIOLOGICAL Plant roots that force into cracks in the cliff (or grow from a seed in a crack) can cause rock fragments to break off as they dislodge the rock. Animals burrowing in the cliff face…