Cliff-top scouring and associated storm deposits are restricted in their development to the exposed outer coast of Orkney. They occur at three sites where cliffs are exposed to the west on the Atlantic coast and one site on the North Sea coast.
The single most important factor determining cliff form on the hard rock coasts of Orkney is the structure of the rock - the way that the rocks are lying and the orientation and number of fractures. The effects can be seen in both plan view - on the map and from above - and in cross section - moving from sea level to the cliff top.
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.
Classic models of the evolution of rocky coasts, like the one below, do not generally reflect the complexity of form on the rocky shorelines on Orkney. This is a reflection of the dominance of hydraulic action over abrasion in coastal erosion and also the variety of coastal configuration on Orkney.
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