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  • 1. Coasts 3 Syllabus: Key Idea: The coast is shaped by weathering, mass movement, erosion, transportation and deposition NT pg 144- 149
  • 2. Lesson objectives:
    • To explain the coastal erosion processes – hydraulic power, abrasion, attrition and solution.
    • To describe the coastal transportation – longshore drift, traction, saltation, suspension and solution.
    • To explain the reasons for coastal deposition.
  • 3. Erosion
  • 4.  
  • 5. Coastal erosion
  • 6. How waves erode …
    • They crash against the rock. Over time, this breaks the rock up
    • They throw sand, pebbles against the rock. This acts like sand paper and wears the rock away = abrasion
    • They force water and air into cracks in the rock. The air is compressed by the surging water and then the air expands explosively as the wave retreats, This weakens joints and cracks and causes the rock to shatter = hydraulic action
    • The sea water dissolves soluble material from the rock. This happens along limestone and chalk coasts when calcium carbonate is dissolved = solution
    • Rocks and boulders already eroded from the coast are knocked together and slowly worn into smaller and rounder pieces = attrition
    • These processes are important only at the base of the cliff.
    • Weathering processes attack the rest of the cliff causing landslips and rockfalls?
  • 7. Reflect….
    • What causes a wave?
    • Why does a wave break?
    • What is the fetch of a wave?
    • What processes are affecting a cliff face?
    • What are the 4 coastal erosion processes?
  • 8. Transportation
  • 9.
    • Loose, eroded materials of all sizes are transported by waves and deposited further along the coast.
    • The methods of travel are the same as in a river channel:
    • Large boulders are rolled along the sea bed = traction
    • Boulders are bounced along = saltation
    • Sand grains are carried in suspension
    • calcium carbonate from limestone and chalk dissolves and is carried in solution
  • 10.  
  • 11. Sand and pebbles are transported along the coast by the process of LONGSHORE DRIFT
  • 12.
    • Waves approach a coastline at an angle
    • Sand grains and pebbles roll back down the beach at right angles to the coastline because due to gravity because it is the steepest gradient
    • As a result material is moved along the coastline
    • The general direction of longshore drift around the coasts of the British Isles is controlled by the direction of the prevailing wind
  • 13.  
  • 14.
    • Waves approach the _____ at an angle due to the direction of the ____. The ______ carry material up the beach at the same angle (due to the wind) and then down at 90 º to the beach (due to the pull of______). This means ______ is carried along the beach in a zig zag pattern.
    TRANSPORTATION Long Shore Drift (LSD) waves wind material coast gravity
  • 15. Deposition
    • The load of the waves (sand, shingle, pebbles) is deposited by constructive waves
    • These waves add more material than they remove from the beach
    • Constructive waves
      • Are long in relation to their height
      • Break gently on the beach so that the swash carrying materials up the beach is stronger than the backwash carrying them away
      • Break gently with between only 6 and 9 waves per minutes
  • 16. Wells next the Sea, Norfolk Slapton Sands, Devon