mass movement

• What are the two types of mass movement?

  Sliding (hard rock coastlines) - due to weathering, rocks break off from the cliff face and slide rapidly downslope along a straight slide plane

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  Slumping (soft rock coastlines) - heavy rainfall saturates rocks like clay, which become weaker and shift downslope along a curved slip plane, forming a ‘scar’ on the upslope and a ‘toe’ on the downslope.
• Describe how mass movement causes cliffs to retreat

  1. Some cliffs are made from permeable rock e.g. clay and which becomes saturated over time due to rain infiltration

  2. Erosion at high tide results in ‘undercutting’ of the base of the cliff which makes it unstable

  3. The increased weight of the saturated rock makes the cliff unstable and eventually results in ‘slumping’ due to gravity

  4. This process continues over time and results in cliff retreat
• How can human activity reduce or accelerate the rate of natural costal processe?

  Hard engineering such as groynes can trap sediment but can also reduce the amount of sediment there is down the coastline, which increases erosion further