Wave-cut Platforms, Notches and Cliffs

• Cliffs are common coastal features. They are formed by a combination of erosion and weathering, weathering working on the upper parts of the cliff and erosion wearing away the base of the cliff.

Photograph of a stack just off shore, showing steep cliff faces on all sides

• Steep cliffs are formed where the land is made up of hard, more resistant, rocks, their height is determined by the difference between the sea level and the level of the land. Hard rocks erode and weather slowly, and the less cracked the rock is, the better it will resist breaking down.
• Igneous rocks such as granite and basalt form rugged vertical cliffs.
• Softer rocks, such as clay, shale and some sandstones erode more easily and can create more gently sloping cliffs.
• Generally though, remember that hard rocks form steep cliffs and soft rocks and badly broken/fractured rocks form more gently sloping cliffs.

• Wave-cut platform, or shore platform is the narrow flat area often seen at the base of a sea cliff or along a large lake shore caused by the action of waves.
• Wave-cut platforms are often most obvious at low tide when they become visible as huge areas of flat rock.
• Sometimes the landward side of the platform is covered by sand, forming the beach, and then the platform can only be identified at low tides or when storms move the sand.
• It forms after destructive waves hit against the cliff face causing corrasion and hydraulic action, creating a wave-cut notch. This notch then enlarges into a cave. The waves undermine this portion until the roof of the cave cannot hold due to the pressure and freeze-thaw weathering acting on it, and collapses, resulting in the cliff retreating landward.
• The base of the cave forms the wave-cut platform as attrition causes the collapsed material to be broken down into smaller pieces, while some cliff material may be washed into the sea. This may be deposited at the end of the platform, forming an off-shore terrace.

  File:Wavecut platform southerndown pano.jpg