Cliffs are shaped by waves acting on complex rock structures. The nature of wave action varies according to the sea state and to the sea bed topography. Waves may arrive at cliffs breaking, plunging and, in deep water, unchanged and different processes of erosion occur under each condition. The up-rushing water from waves impacting on the cliff itself generates powerful hydraulic forces and the deluge of water on the cliff top washes and removes loose debris to create a scoured zone. During big storms, debris is removed from the edge of the cliff top and washed inland to form spreads or ridges of boulders. These cliff-top storm deposits give way inland to dumps of angular gravel and finally turf littered with pebbles and granules of air thrown debris.
Cliffs also can be regarded as rock walls subject to all the forces of rock mechanics. The cliff is affected by mass movement, especially by processes associated with lithologies with high rock mass strength. The cliff faces above the limit of common wave wash is also subjected to weathering. The influence of salt water spray may be particularly important here.
Definition: subaerial processes of fall, slide, flow and creep that transfer debris to the foot of a slope