Coastal Erosion Processes

Erosion is the wearing away and removal of material from the coastline by natural processes. At A-Level, you must understand not only the marine processes that erode the coast directly, but also the sub-aerial processes (weathering and mass movement) that weaken rock and contribute material to the coastal system. The interplay between marine and sub-aerial processes determines the rate and pattern of coastal retreat.

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Marine Erosion Processes

Marine erosion occurs where waves attack the coastline. There are four principal mechanisms:

1. Hydraulic Action (Wave Quarrying)

Hydraulic action is the sheer force of water striking rock surfaces. When waves crash against a cliff face, water is driven into cracks, joints and bedding planes under enormous pressure. As the wave retreats, the compressed air within these cracks expands explosively, progressively widening the fissures and eventually causing blocks of rock to fracture and detach.