CGP Coastal Processes

• Coastal processes

  Caused by the sea (erosion and deposition) and sub-aerial processes (caused by the sea and weathering)
• Six main ways waves erode the coastline

  • Corrasion (abrasion)
  • Hydraulic action
  • Cavitation
  • Wave quarrying
  • Solution (corrosion)
  • Attrition
• Transportation of eroded material

  1. Solution

  2. Suspension

  3. Traction

  4. Longshore drift
• Swash

  Carries sediment (sand, shingle, pebbles) up the beach, parallel to the prevailing wind
• Backwash

  Carries sediment back down the beach, at right angles to the shoreline
• Angle between prevailing wind and shoreline


  Causes a few rounds of swash and backwash to move sediment along the shoreline
• Deposition


  When material being transported is dropped on the coast
• Types of deposition

  • Marine deposition
  • Aeolian deposition
• Sediment load exceeds ability of water or wind to carry it


  Causes deposition
• Friction increases

  Causes water or wind to slow down
• Flow becomes turbulent


  Causes water or wind speed to decrease
• Wind drops

  Wave height, speed and energy will decrease
• Types of sub-aerial weathering

  • Salt weathering
  • Freeze-thaw weathering
  • Clay weathering
  • Chemical weathering
• Mass movement

  Shifting of material downhill due to gravity
• Types of mass movement

  • Landslides
  • Slumping
  • Rockfalls
  • Mudflows
  • Soil creep
• Unconsolidated rocks are prone to collapse as there's little friction between particles to hold them together
• Heavy rain can saturate unconsolidated rock, further reducing friction and making it more likely to collapse
• Runoff can erode fine particles and transport them downslope