coasts

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  • coasts
    • coastal weathering/ erosion
      • weathering is where rocks are damaged where they are, erosion takes away excess
      • mechanical weathering: freeze-thaw. (water freezes in faults and expands it)
      • chemical weathering: carbonation weathering. (rainwater has CO2 in it so bonds with calcium carbonate in rock to dissolve it)
      • mass movement - rocks fall down causing coasts to retreat. Three types: slide, slump and rockfall.
      • (only destructive) waves use hydraulic action (air compressed and expands rock), attrition (particles rub together to get smaller) and abrasion (particles scrape against rock to remove bits)
      • destructive waves have higher frequency and a more powerful backwash to carry things away.
      • wave-cut platforms made as waves cause most erosion at bottom of cliff making a notch which then grows and collapses the material above until a platform is found
      • soft rocks such as clay is eroded more quickly to form a bay whereas hard rock such as chalk forms headlands.
      • on a headland, there will be faults that become bigger from abrasion and hydraulic action to form caves, arches, stacks and stumps.
    • coastal transport/ deposition
      • transportation through longshore drift occurs when there is a prevailing wind that causes the swash to be at an angle.
      • traction - rolling rocks. saltation - bouncing rocks. suspension - carried in water. solution - dissolved in water
      • deposition happens when the wave doesn't have enough energy to carry sediment so leaves it. deposition increases when there's lots of erosion and transportation
      • constructive waves deposit material as they're low and long and their swash is powerful compared to backwash meaning sediment can't be taken back down the beach.
      • beaches are found between the high water mark (highest point of land the sea gets to) and the low water mark (lowest point) by constructive waves
      • sand beaches are gently sloping and flat as the material can be easily moved whereas shingle beaches are steep as the backwash can't move them back down the beach.
      • spits are formed by longshore drift at sharp bends in the coastline. a bar is a spit that joins two headlands together to form a lagoon behind it.
      • sand dunes are also formed by longshore drift as sand colonises around plants to form embryo dunes which move inland over time to form mature dunes.
    • identifying landforms
      • stacks look like blobs in the sea, cliffs are shown as black lines, wave cut platforms are shown as bumpy edges.
      • sand beaches are pale yellow, shingle beaches are shown as speckles. spits are shown as an extension of land
      • example of an arch - durdle door in dorset. Old harry is a stack and old harry's wife is a stump.
      • lulworth cove is an example of a bay, chesil beach is a bar with the fleet lagoon behind it.
    • coastal management strategies
      • hard engineering is man-made, soft is when schemes are set up with knowledge of the sea
      • sea wall - wall that reflects waves to prevent erosion and flooding but they're expensive to maintain
      • gabions -  rocks in a cage that absorb energy to reduce erosion cheaply but they're ugly and corrode
      • rock armour - boulders that absorb wave energy to stop erosion and flooding but can be moved around with strong waves
      • groynes - fences built at right angles to trap material to create bigger beaches and therefore slower waves and protection from erosion / flooding but may starve beaches of sand elsewhere.
      • beach nourishment - sand added to upper beach from lower partto make bigger beaches for greater protection but can kill organisms and is expensive as it has to be repeated
      • dune regeneration - planting vegetationto provide a barrier, stabilisation is cheap but nourishment is expensive and can only cover small area
      • managed retreat - allowing area to flood to protect area behind it and is cheap and easy but causes anger over certain lands being lost.

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