Coastal Landforms

  • Created by: 15changj
  • Created on: 21-09-19 09:49

Formation of Headlands and Bays

  • Rocks of different resistance in alternating layers lay at right angles to the sea 
  • The sea erodes the rocks through the process of hydraulic action and abrasion.
  • Less resistant rock is erroded at a faster rate
  • Creates inlet in soft rock known as bay
  • Areas of hard rock left jutting out in sea known as headlands
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Formation of Headlands and Bay

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Formation of a Sea Stack

  • Natural cracks in headland
  • Sea attacks cracks through processes of hydraulic action and abrasion
  • Erosion is caused by pressurised air and powerful waves
  • Expands crack to create a cave in side of headland
  • Over time the cave is erroded all the way through the headland
  • Creates an arch
  • Arch is unsupported and subaerial processes such as rain can lead to the top of the arch becoming saturated with water
  • Top of the arch becomes heavy and along with the force of gravity can lead to the top of the arch collapsing
  • Leaves behind an isolated stack of rock - a sea stack
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Formation of a Sea Stack

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Formation of a Wave-Cut Platform

  • Waves hit base of cliff 
  • Leads to erosion of base of cliff as they are pounded rocks, waves and pebbles.
  • Abrasion and hydraulic action leads to formation of a wave-cut notch
  • Erosion continues and an overhang develops
  • Overhang increases in size
  • Pressure on overhang increases due to sub-ariel processes e.g. heavy rainfall
  • Rock is unable to support itself 
  • Rock collapses
  • Process occurs again
  • Leaves a layer of rock (wave-cut platform) at foot of cliff over time
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Formation of a Wave-Cut Platform

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Formation of a Coastal Spit

  • Longshore drift moves sediment down a coastline due to the angle of prevailling wind
  • When coastline changes direction longshore drift deposits sand in the sea 
  • Over time sand is deposited out at sea creating a long ridge of sand (spit)
  • Spit eventually ends when sand reaches an area of water with high energy (e.g. river estuary)
  • Area of water behind spit is sheltered and eventually forms a salt marsh
  • Spit sometimes changes direction due to change in prevailling wind - creates hooked end
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Formation of a Coastal Spit

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Formation of a Coastal Bar

  • Longshore drift moves sediment down coastline due to angle of prevailling wind
  • When coastline changes direction longshore drift moves and deposits sand in the sea 
  • Coastal bar - ridge of sand that grows across a bay due to longshore drift
  • Often creates a shallow lake (lagoon) behind them
  • Lagoon eventually fills up with sediment or storm waves break through bar leaving lagoon exposed to sea
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Formation of a Coastal Bar

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