Hengisbury Head Coastal Processes

Category: Force, Geology, Nature, Water

Last Updated: 19 Jan 2017

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What are geomorphic processes and how do they affect the coast at Hengistbury Head? Setting the scene Hengistbury Head is a scenic and historic headland near the town of Bournemouth on the south coast of England. It stands mid-way between Poole harbour and Hurst spit and forms the main division between Poole and Christchurch Bays. Coastal Processes| Description| Sub Aerial | Coastal erosional processes that are not linked to the action of the sea. Erosion occurs via rain, weathering by wind and frost. Its impact is often seen in soil creep, slumping and landslides. Corrosion| When waves approach the coastline they are carrying material such as sand, shingle, pebbles and boulders. Abrasion occurs when this material is hurled against cliffs as waves hit them, wearing the cliff away. | Human activity| Much building and recreation occurs at the coast, and this increases pressure on cliff tops, making them more liable to erosion and subsidence. The building of sea defences upsets the dynamic equilibrium of the coastline| Hydraulic pressure| Cliffs and rocks contain many lines of weakness in the form of joints and cracks.

A parcel of air can become trapped/compressed in these cracks when water is thrown against it. The increase in pressure leads to a weakening/cracking of the rock. | Corrasion| When waves approach the coastline they are carrying material such as sand, shingle, pebbles and boulders. Abrasion occurs when this material is hurled against cliffs as waves hit them, wearing the cliff away. | Coastal Transport| Description| Solution| Minerals are dissolved in seawater and carried in solution. The load is not visible.

Load can come from cliffs made from chalk or limestone, and calcium carbonate is carried along in solution. | Suspension| Small particles are carried in water, e. g. silts and clays, which can make the water look cloudy. Currents pick up large amounts of sediment in suspension during a storm, when strong winds generate high-energy waves. | Saltation| Load is bounced along the seabed, e. g. small pieces of shingle or large sand grains. Currents cannot keep the larger and heavier sediment afloat for long periods. | Traction| Pebbles and larger sediment are rolled along the seabed. |

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