caves, arches, stacks and stumps

• caves, arches, stacks and stumps are examples of erosion
• caves, arches, stacks and stumps:

  features created through erosion of a headland
• example of caves, arches, stacks and stumps:

  caves, stack and stump: Old Harry's rocks (the stacks) at the foreland and arch at Durdle Door, Dorset
• characteristics of a cave:

  • wide entrance becoming smaller further back
• characteristics of an arch:

  • unsupported top of the arch
  • wide base with wave-cut notches
  • water goes all the way through
  • arch is part of the headland
• characteristics of stacks:

  • detached pillars / blocks off a headland
  • several metres high
  • wave cut notches at base
• stage 1

  a large crack is enlarged by the pressure on / off effect of hydraulic action
• stage 2

  the crack grows into a notch and then a cave as destructive waves converge on the headland and continue to erode it
• stage 3

  over time, the cave becomes larger. wave refractions draws waves to all sides of the headland so caves may form back to back
• stage 4

  the sea breaks through the back of the caves forming a natural arch. the base is widened as notches form
• stage 5

  weathering such as freeze-thaw continues to weaken the top of the arch, making it less stable
• stage 6

  the top of the arch eventually collapses
• stage 7

  this leaves a pillar of detached rock called a stack
• stage 8

  notches form at the base of the stack which eventually makes it unstable
• stage 9

  the stack will eventually topple into the sea, leaving only its base. this stump is normally only visible at low tide
• label this diagram:

  here ganggg

  A) large crack, hydraulic action

  B) crack grows

  C) cave becomes larger

  D) breaks through headland and forms arch

  E) arch erodes and collapses

  F) leaves tall stack

  G) stack erodes and forms stump

  
• what does this picture show?

  caves, arches, stacks and stumps