mechanical weathering

• What is frost shattering?

  • Water enters a crack or joint in the rock when it rains and then freezes in cold weather
  • when water freezes it expands in volume by 10%, exerting pressure on rock and forcing the crack to widen
  • rock breaks
  • TAKES A LONG TIME
• What is salt crystallisation?


  • When salt water evaporates, it leaves salt crystals behind
  • these can grow over time and exert stresses in the rock, causing ice to break up
  • salt can also corrode rock especially if it contains iron traces
• What is WETTING AND DRYING?


  Frequent cycles of wetting and drying are common on the coast

  Rocks rich in clay (eg shale) expand when they get wet and contract as they dry

  This can cause them to crack and break up