- Created by: moonbow0701
- Created on: 15-11-18 18:02
How are Headlands & Bays formed?
- Some rocks on the coast are tougher and more resistant than others, for example, chalk, sandstone, and granite are hard and clay is much weaker
- Different types of rock are eroded at different rates. The softer rocks are eroded by hydraulic action much faster causing the cliff to retreat.
- The hard rock erodes much slower which creates headlands, the softer rock continues to erode quickly which creates the bay.
- The hard rocks erode slowly over time but eventually, they are undercut by the waves causing them to fall and create stacks. The stacks and headlands take the most impact from the oncoming waves which slows down as it flows into the bay, sediment are deposited here creating sheltered beaches.
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How are Stacks and Stumps formed?
- A joint or fault in the resistant rock
- Hydraulic action widens the faults as well as weathering
- This continues and sea caves being to form this is because the waves undercut the cliffs
- The waves eventually undercut through the cave and form arcs
- This continues and the arcs continue to grow in size, different types of weathering also result in the arc collapsing
- After the arc collapses a stack is formed if hydraulic action and weathering continue stumps are formed and they eventually disappear
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Development of Wave Cut Platforms
- Abrasion occurs between high and low tide - rocks are hauled at the base of the cliffs
- Cliff starts to become 'stressed' because the base has been eroded away, the cliff face eventually falls exposing the rock behind it.
- The cliff face is eroded into smaller bits of rock, these small bits of rock are part of a process called abrasion which erodes the wave cut platform more and more.
- The cliff face will retreat slowly over time and wave cut platforms are constantly eroded and the cycle repeats.
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How are Beaches formed?
- Sediment is transported by longshore drift, this is done by the swash, this carries sediment up the beach as it has power. Then it deposits the sediment as it has no power left. The backwash pulls back some sediment and the process repeats again. The waves are caused by the southeast prevailing winds.
- Groynes slow down this process as they decrease the amount of sediment that is spread across
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How are Spits formed?
- Longshore drift moves material along the coastline.
- A spit forms when the material is deposited.
- Over time, the spit grows and develops a hook if the wind direction changes further out
- Waves cannot get past a spit, which creates a sheltered area where salt marshes form.
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How are Sand Dunes formed?
- Embryo dunes form around deposited obstacles such as pieces of wood or rocks. These develop and become stabilized b vegetation to form foredunes and tall yellow dunes. Marram grass is adapted to the windy, exposed conditions and has long roots to find water. These roots help bind the sand together and stabilize the dunes. In time, rotting vegetation adds to organic matter to the sand making it more fertile. A much greater range of plants colonize these back dunes. Winds can form a depression in the sand called dune slacks.
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How are Bars formed?
- Longshore drift may cause a spit to grow right across a bay, trapping a freshwater lake (or lagoon) behind it. This feature is called a bar. An offshore bar forms further out to sea. Waves approaching a gently sloping coast deposit sediment due to friction with the seabed. Occasionally, longshore drift may cause a spit to grow right across a bay.
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