weathering and wind processes

notes on the main processes for wind and weathering

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insolation

  • high temperatures during the day heat up the rock which makes it expand
  • cool temperatures at night cause the rock to contract
  • this constant repeating of expanding and contracting causes stress and makes the layers of rock peel off- flaking. this happens by block disintegration (larger rocks break under constant stress) and granular disintegration (when the small minerals in the rock move due to them being different shades, the darker ones become hotter and stress more)
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crystal growth

  • high temperatures draw saline (salty) water to the surface, causing the water to evaporate, leaving the salt behind
  • the salt gets into cracks and salt crystals start to grow, this puts stress on the rocks and minerals leading to block and granular disintegration
  • along with insolation weathering this causes flaking
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frost thaw

  • this happens when there is large differences bwetween day and night temperatures
  • water trapped in rocks freezes over night and expands
  • at day the ice melts and the rocks contract again
  • this repeats causing the constant build up and let down of stress on the rocks until it breaks under this stress.
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Hydration

  • minerals in rocks expand when the absorb water, putting the surrounding rocks under more stress
  • this build up of stress causes the rocks to snap
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wind processes- creep

  • a bit like traction transport in rivers
  • this is when sand grains slide and roll across the surface
  • this happens due to small differences in pressure close to the surface creating lift
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wind processes- saltation

  • this is the bouncing of material across the ground at high wind speeds
  • when sand grains hit the surface, they cause more sand grains to start saltating
  • saltation is one of the key processes that form sandunes
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wind processes-suspension

  • small dust particles carried by  wind in dust storms
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deflation

  • this is when the wind removes loose particles of sand and material  from the surface.
  • this helps to form desert pavements, as it removes all small loose material, leaving only the large material behind.
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