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UK Landscapes (Formation of a spit (1) Spits form at sharp bends in the…
UK Landscapes
Formation of a spit
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4) The sheltered area behind the spit is protected from waves - lots of material accumulates in this area, which means plants can grow there.
5) Over time, the sheltered area can become a mud flat or salt marsh.
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Chemical weathering is the breakdown of rock by changing its chemical composition. Carbonation weathering is a type of chemical weathering that happens in warm and wet conditions...
1) Rainwater has carbon dioxide dissolved in it, which makes it a weak carbonic acid.
2) Carbonic acid reacts with rock that contains calcium carbonate, so the rocks are dissolved by the rainwater.
Headlands and bays form where there are alternating bands of resistant and less resistant rock along a coast.
The less resistant rock, e.g. clay, is eroded quickly and this forms a bay - bays have a gentle slope.
The resistant rock, e.g. chalk, is eroded more slowly and it's left jutting out, forming a headland - headlands have steep sides.
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Mechanical weathering is the breakdown of rock without changing its chemical composition. There's one main type of mechanical weathering that affects coasts - freeze-thaw weathering...
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Mass movement is the shifting of rocks and loose material down a slope, e.g. a cliff. It happens when the force of gravity acting on a slope is greater than the force supporting it.
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Waves cause most erosion at the foot of a cliff. This forms a wave-cut notch, which is enlarged as erosion continues.
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Deposition is when material being carried by the seawater is dropped on the coast. It occurs when water carrying sediment slows down so that it isn't moving fast enough to carry so much sediment.
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Constructive waves
Features
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Backwash is weaker and doesn't take a lot of material back down the coast; this means material is deposited.
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Repeated erosion and enlargement of the cracks in the rocks causes a cave to form. Continued erosion deepens the cave until it breaks through the headland - forming an arch, e.g. Durdle Door in Dorset. Erosion continues to wear away the rock supporting the arch, until it eventually collapses. This forms a stack - an isolated rock that's separate from the headland, e.g. Old Harry in Dorset.