Coastal Processes and Landforms- slides

• Fetch


  The distance over which the wind has blown
• Wave energy


  Depends on the fetch, the strength of the wind and the length of time over which the wind has blown
• Waves break when the bottom of the wave touches the sand, slows down and the top of the wave topples over

  
• Swash


  The movement of water up the beach
• Backwash


  The movement of water down the beach, always at right angles to the beach
• Destructive waves


  • Backwash > swash
• Constructive waves


  • Swash > backwash
• Processes of erosion


  • Attrition
  • Hydraulic action
  • Abrasion
  • Corrosion
• Attrition


  Material carried by the waves bump into each other and so are smoothed and broken down into smaller particles

  
• Abrasion/Corrasion


  The process by which the coast is worn down by material carried by the waves. Waves throw these particles against the rock, sometimes at high velocity

  
• Hydraulic action


  The force of water against the coast. The waves enter cracks (faults) in the coastline and compress the air within the crack. When the wave retreats, the air in the crack expands quickly causing a minor explosion

  
• Corrosion


  The chemical action of sea water. The acids in the salt water slowly dissolve rocks on the coast. Limestone and chalk are particularly prone to this process
• Landforms of coastal erosion

  • Headlands and Bays
  • Cliffs and Wave Cut Platforms
  • Caves, Arches, Stacks and Stumps
• Headlands and bays


  Formed by differential erosion of different rock types

  
• Cliffs


  Formed by the waves attacking the base of the cliff through abrasion, corrosion, hydraulic action and attrition, undercutting the cliff and causing it to collapse
• Wave-cut platform


  Formed as a result of further cliff retreat after the cliff has collapsed
• Formation of caves, arches, stacks and stumps


  1. Waves erode faults (cracks) in the headland

  2. Waves erode through the headland to form an arch

  3. The arch becomes unsupported and collapses to form a stack

  4. A stump is formed from the collapsed stack
• Caves, arches, stacks and stumps are formed in sequence as a headland is eroded
• Longshore drift


  The movement of sediment along the coastline
• Backwash is always at right angles to the beach
• Landforms of coastal deposition

  • Beaches
  • Spits
  • Tombolos and Bars
• Beaches


  Form in sheltered environments, such as bays, when the swash is stronger than the backwash
• Spits


  Formed by longshore drift, curved due to changing wind direction
• Tombolos


  A spit that joins the mainland to an island
• Bars


  A spit that joins one part of the mainland to another
• The river's current stops deposition across an estuary, preventing a spit from growing across it
• The majority of wave cut platforms are less than 2 kilometres in length