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Coastal Processes (Processes (Solution (This is a weathering process , it…
Coastal Processes
Processes
Solution
This is a weathering process , it is included here because it leads to coastal erosion. It occurs when rocks contain minerals that can be dissolved by salts in the sea water.This is mainly true for limestone or chalk coasts.
Differential Erosion
occurs since the rocks are eroded at different rates. The less resistant rocks undergo most erosion and retreat inland to form bays.The more resistant rock stands out as headlands.
Abrasion
sand, pebbles and boulders carried by the waves are thrown against the coast causing abrasion.
Hydraulic action
Is when the power of the waves erodes the coast.When waves hit the coast they create pressure of up to 25 tonnes.Its most effective where the rock has bedding planes , joint and faults.Cracks are widened and loose material is broken away.
Air compression
Air is trapped in the cracks and compressed. As the waves retreat, the air expands. This causes an explosive effect , which weakens the rock further
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WAVES: are produced by friction between wind and the surface of the sea. This results in the transfer of moving air to the water
the size and power of waves depends on; the strength of the wind as it blows onshore, and on the fetch of the wave
Fetchis the length of open water over which wind can blow unobstructed. the largest waves are produced where there is a long fetch accompanied by strong wind
Waves become steeper as they reach the shore due to the sea becoming shallower. When waves become unable to support themselves theybreak onto the shore
water is thrown forward by an incoming wave called the swash. the water that runs back toward the sea is called backwash
Types of Waves
Destructive waves:
erosional waves.
they're high (<1 metre).
short wavelength (>20metres).
plunge vertically onto the shore. high frequency (10-12 every min).
backwash is stronger than swash.
caused by local winds and storms
Constructive Waves:
depositional waves.
flat and low (>1metre)
long wavelength (100 metres)
spill gently onshore
backwash weaker than swash
caused by swell of distant storms
Wave Refraction:process by which waves bend and change as they approach the shore.
friction with seabed causes waves to slow. the part of the wave in shallow water move
more slowly then water in deep part resulting in wave refraction (bending).
at bays and headlands waves first meet shallow water in front of the headlands. the waves converge on the headland and use up most of the energy = erosion.
the opposite happens in a bay, waves spread out and use up less energy.deposition happens = forms beaches.
eventually, erosion of headlands and deposition in the bays straighten an irregular coastline.
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Sea stacks
the sea arch is enlarged as the processes of erosion continue. the roof is also weakened by weathering. Eventually the the seaward portion is cut off from the coastline and is left standing as a sea stack.
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Coastal Erosion
Hard coastlines consist of rock outcrops, rocky cliffs or structures that include sea walls, piers etc. rate of erosion is slow
soft coastlines consist of clay cliffs, shingle beaches, sandy beaches and sand dunes.
a lot of erosion
Sea arches
Are formed when to back to back caves form on opposite sides of the headland.
If the area of weakness cuts through a narrow headland, a cave may grow in length until it extends through to the other side, to form a bridge like feature called a sea arch.
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