coastal cliff

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Steep slope rising from the sea to a considerable height, and consisting of either bare rock or an accumulation of deposited material such as clay. The nature of the cliff depends on a number of factors such as the nature of the rock (its strength, weaknesses in the rock and bedding planes), its exposure to waves, and whether any coastal protection measures have been used.

Limestone has a well-developed jointing and bedding structure and forms geometric cliff profiles with steep, angular cliff faces, and flat tops. Coastal erosion causes complete blocks to fall away resulting in angular overhangs such as those at Tresilian Bay, Llantwit Major, Wales. The rate of cliff retreat is much more rapid in chalk, and steep cliffs are created by erosion and landslides. Cliffs can also be found in areas of softer rock such as the clay cliffs of Norfolk and Holderness, England.

The dip of rock bedding planes also affects the cliff profile. If beds dip vertically, a sheer cliff face will be formed, as at the Old Red Sandstone cliffs in Dyfed, Wales. If they dip steeply seaward then steep, shelving cliffs will occur, as at the cliffs at Tenby, Wales.

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