3.2 Weathering and Rocks

• weathering


  process by which exposed rocks are broken down on the spot by rain, frost, wind and other elements of the weather
• decomposition


  chemical weathering that creates altered rocks from the weathered material
• disintegration

  break-up of rocks into smaller fragments, although rocks stay the same chemical structure
• chemical weathering


  form of weathering brought about by chemical attack of rocks usually by presence of water
• granite


  hard, resistance, igneous rock consisting of felspar
• mechanical weathering


  includes processes as freeze-thaw and exfoliation or onion-skin, leads to breakdown of rocks but doesnt change composition of rock
• scree


  describes angular sediment that collects at the foot of a mountain range or cliff
• biological weathering


  form of weathering cause by the activity of living organism.
• interrelated


  when a number of factors interact to gave an impact on some feature
• clastic


  rocks and sediments are composed of fragments of pre existing materials and rocks
• plastic


  describes permanent change in the shape of a rock
• freeze-thaw


  form of physical weathering, common in mountains and glacial environments, caused by expansion of water as it freezes
• salt crystallisation

  decomposition by rocks by solutions of salt
• salt crystal growth

  breakdown of rock by expansion and contraction of salt crystals due to fluctuation in temperatures
• healing and cooling


  expansion and contraction of rocks or materials due to repeated expansion and contraction
• exfoliation


  expansion of rocks in deserts due to heating and cooling at day and night. rock "peel"
• pressure release


  process by which underlying rocks are split by the removal of large weights on top of them such ad glaciers, ice sheets and overlying rocks
• unloading


  reduction in pressure on rocks by the removal of overlying rocks
• pseudo- bedding planes

  horizontal craxks in rocks formed by the pressure release
• vegetation roots

  may weather rocks by their physical growth and through secretion organic acids
• carbon-bicarbonate


  chemical that is vulnerable to solution in acidic conditions
• hydrolysis


  type of chemical weathering in which feldspar is converted to kaolin
• kaolin


  impact of hydrolysis on granite changes feldspar into kaolin
• hydration


  form of chemical weathering which certain materials absorb water and change
• Van't Hoff's Law


  states that rate of chemical weathering increases 2-3 times for every increase in temp of 10 degrees to 60
• Differential resisitance


  refers to how some rocks and minerals are more resistant to others.