Friday, 13 December 2013

The Impact

Coastal erosion will change the landform of the coastal. Some coastal landforms serve as natural erosion protective features, minimizing the amount of coastal erosion to land and structure behind them. These includes beaches and dunes, bluffs, stacks, stumps, caves, offshore bars, spits and shoals, bays and headlands, and coastal wetlands and the vegetation on them.

Bays and headlands
Headlands form along coastlines in which bands of soft and hard rock outcrop at right
angles to the coastline (see image below). Due to the different nature of the rock erosion
occurs at different rates. Less resistant rock (e.g. boulder clay) erodes more rapidly than
less resistant rock (e.g. chalk).

Stack, stump and caves
-These features are formed on cliffs or headlands. Waves attack vertical lines of weakness in the rock known as faults. Processes such as hydraulic action and abrasion widen these faults into cracks and eventually the waves will penetrate deeply enough to create caves.

-Over time, the cave will be eroded into an arch, accessible to the sea on both sides.  Weathering will also play a role, with physical weathering processes such as freeze thaw and salt crystallisation and chemical processes such as carbonation weakening the rock surrounding the cave or arch making it more susceptible to mass movement and collapse.

-Finally, the erosion and weathering continues and the arch collapses leaving behind a stack (a vertical column of rock) .  These stacks can be attacked further, and eventually the stack may collapse to leave a low lying stump. 

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