Landforms Of Erosion

Question 1

Describe how a Cave, Arch, Stack and Stump are formed

Answer 1

1. A crack is formed in the side of the headland by marine erosion.
   In particular by processes such as hydraulic action and abrasion. Waves and currents are the main SOE here
2. Over time the cracks will be enlarged by further marine erosion. The process of wave refraction will accelerate erosion rates – this is an example of positive feedback
3. In time the caves will be eroded through the headland – the main component in this system - to produce another component called an arch
4. Sub-aerial erosional processes such as salt weathering and freeze thaw weathering will weaken the arch roof. Eventually it will collapse and the material will be transported away by the energy of the waves. This is a transfer of sediment – perhaps by the rip current. This leaves an isolated sea stack
5. Eventually the only remaining component is a stack. This has been weathered by sub-aerial processes. Marine erosion will attack the base of the stack causing it to collapse. Any sediment transferred out of the system will be an output

Question 2

Describe Wave Refraction

Answer 2

As waves approach a coast they are refracted so that their energy is concentrated around headlands but reduced in the bays. So erosion occurs on headlands and deposition in bays.