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EQ2: How do characteristic coastal landforms contribute to coastal landscapes? GapFill
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waves have a long wavelength, small height and low frequency. Their swash is stronger than the backwash, pushing material forwards and upwards, and water percolates across the large swash area. They often ‘spill’ onto the beach, rather than plunge, and, therefore, build up the beach.
waves are frequent waves with a short wavelength. They plunge down onto the beach, eroding sediment with a strong backwash. They can create a steep beach profile as material is gouged away, and swash is reduced because incoming waves meet the strong backwash.
Where the cliffs are exposed to the waves, abrasion, hydraulic action and solution create a at the base of the cliffs. Eventually, it grows too big to support the overburden, and the surface layer of the cliff collapses, exposing a fresh surface for erosion. The rock fallen at the bottom of the cliff is then worn down and away. Over time, the cliffs retreat.
platforms (also known as shore platforms) are the remains of eroded cliffs. They are very gently sloping sheets of rock which can be further eroded by abrasion.
After the formation of a headland, a small crack can form in the side of the headland called a geo as weakness in the rock is exploited by action and other erosion processes. Over time, the geo expands into a large hole called . Sometimes, erosion is forced upwards to the surface, creating .
Sometimes, two caves erode backwards, or one cave makes its way all the way through, forming . Over time, the hole gets bigger through erosion and subaerial weathering, and the top section collapses. There’s now a column of rock, separated from the land, called .
The stack is gradually eroded until it collapses. Subaerial processes and mass movement reduce its height, while the waves thin the base through hydraulic action, corrasion and abrasion, and solution, until the stack collapses. The collapsed material is eventually worn away until is left behind, on top of the wave-cut platform.
Sediment reaches the coasts from many different sources. Most of the material comes from . This is material that is eroded inland and in the uplands, and is transported out to the sea. If you have ever been to a coast after a storm, you will have seen that the rivers run brown into the sea. Humans can influence the rate of coastal erosion by building dams.
Some material does come from the , especially when they are made of soft material such as boulder clay – the randomly packed silt and boulders left behind by retreating glaciers thousands of years ago. Hard cliffs will provide very little material in comparison.
Other sources include material from sinks such as beaches, which is moved by longshore drift and currents; from estuaries; from offshore – the seabed and sandbanks; and from shells and corals – biological origin.
Within the coastal environment, there are essentially closed systems called (or littoral cells). They have boundaries such as deep water or headlands. However, they do have sources of material, sinks and flows, and processes such as erosion and deposition, and transport. There are 11 major cells in England and Wales, some of which can also be divided into subcells.
Each stretch of coast has a sediment – the difference between the amount of material added and the amount of material removed. Areas where material is deposited are called sinks. Material is transferred from sources to sinks.
Positive budgets mean there is more material deposited than removed, so the coastline builds up. The opposite is true for negative budgets – increased removal means that the coastline recedes.