2B.4C: Coastal Landscapes Produced by Erosion

• Cave-arch-stack-stump sequence


  1. Large crack, opened up by hydraulic action
  2. The crack grows into a cave by hydraulic action and abrasion
  3. The cave becomes larger
  4. The cave breaks through the headland, forming a natural arch
  5. The arch is eroded and collapses (e.g. Durdle Door, Dorset)
  6. This leaves a tall rock stack (e.g. Stack Rocks, Pembrokeshire)
  7. This stack is eroded, forming a stump (e.g. Old Harry Rocks, Dorset)
• Wave cut notch

  • A wave cut notch is a curved indentation of about 1-2 m high extending along the base of a cliff. It forms between the high tide and low tide marks, where destructive waves impact against the cliff.
  • It's eroded by hydraulic action and abrasion, and in some cases corrosion.
  • The depth of the notch varies depending upon the resistance of the rock at different points.  
• Wave cut platform

  • A flat rock surface exposed at low tide, extending out to sea from the base of a cliff. 
  • The notch deepens by further erosion until the overlying material collapses by mass movement due to gravity, forming a cliff. 
  • The process repeats, and the position of the cliff retreats (coastal recession)
  • The rock just below low tide level is always submerged, it's uneroded as it's never exposed to wave impact. 
  • As the overlying material is eroded, uneroded rock at low tide level is left as flat rock surface, the wave cut platform.