Weathering and Mass Movement Processes

• Weathering is the breakdown of rocks (mechanical, biological or chemical) over time, leading to the transfer of material into the littoral zone, where it becomes an input to sediment cells.
• Positive Feedback:

  If the rate of removal of the weathered rock from the base of the cliff is higher than the rate of weathering, then this will promote further weathering as this will increase the area of exposed rock . This will increase the amount of erosion that occurs because this will increase the supply of rocks which can become part of the erosive processes of saltation and abrasion.
• Negative Feedback:

  • If the removal of weathered rock from the base of the cliff is slower than the rate of weathering then this will lead to a build up of debris at the base of the cliff , reducing the exposed cliff area and therefore reducing the rates of weathering . It will also reduce erosion as the cliff foot will be protected from the other forces of erosion
• Freeze-thaw (Frost-Shattering): Water enters cracks in rocks and then the water freezes overnight during the winter. As it freezes, water expands by around 10% in volume which increases the pressure acting on a rock, causing cracks to develop. Over time these cracks grow, weakening the cliff making is more vulnerable to other processes of erosion
• Salt Crystallisation: As seawater evaporates, salt is left behind. Salt crystals will grow over time, exerting pressure on the rock, which forces the cracks to widen. Salt can also corrode ferrous (materials that contains iron) rock due to chemical reactions
• Chemical Weathering: The breakdown of rocks through chemical reactions
• Biological Weathering: The breakdown of rocks by organic activity:
• Mass movement is the movement of material down a slope under the influence of gravity . Mass movement can be categorised into four main areas: creeps, flows, slides and falls.
• The type of mass movement is dependent on:

  ● Cliff/slope Angle

  ● Rock Type

  ● Rock Structure

  ● Vegetation

  ● Saturation of Ground

  ● Presence of Weathering
• The Different Types of Mass Movement are:

  • Soil Creep
  • Solifluction
  • Mudflows
  • Rockfall
  • Landslide
  • Landslip or Slump
  • Runoff