Stacks

Cards (12)

  • Hydraulic action is a process where pounding waves compress trapped air in the rocks, creating an explosive blast which weakens and loosens rock fragments.
  • Abrasion is a process where rock fragments are thrown against the headland, breaking down the cliff face and wearing away the rock.
  • Solution is a process where salts in sea water dissolves rock.
  • Attrition is a process where rock fragments are slowly ground down by friction from wave action into smaller and rounder pieces which can then be used as an abrasive material.
  • Rocks contain weak points that are more easily eroded.
  • Over time, lines of weakness are enlarged and develop into small sea caves.
  • In some cases, a blowhole can form in the roof of the cave as compressed air is pushed upwards by the power of the waves, causing vertical erosion.
  • There may be erosion on both sides of the headland due to wave refraction until eventually the sea cuts through the back walls of the caves, forming an arch.
  • Continued erosion enlarges the arch.
  • The base of the arch is also undercut by the erosion, causing the arch to become unsupported.
  • Eventually the arch collapses due to gravity to form a stack.
  • Old Harry is an example of a stack.