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Freeze Thaw Weathering &Solution Weathering

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Freeze Thaw Weathering &Solution Weathering

  1. 1. Freeze Thaw Weathering & Solution Weathering
  2. 2. Freeze thaw weathering usually occurs in the winter months when the temperatures decrees and there is usually more rain, or in mountainous areas. Freeze Thaw Weathering
  3. 3. The first process which occurs in freeze thaw weathering is when water becomes trapped in small cracks or weaknesses in the rock. Freeze Thaw Weathering
  4. 4. Freeze Thaw Weathering Next, at night, when the temperatures drop below 0 degrees centigrade the water freezes and turns into ice, as the water freezes it expands by 9% in volume. This causes pressure on the rock.
  5. 5. Freeze Thaw Weathering Then during the day the the ice melts and contracts by 9% in volume, this releases the pressure on the rock. And the process repeats itself over and over again until eventually large cracks begin to form in the rock.
  6. 6. Freeze Thaw Weathering Over time the process of alternating expansion and contraction of the rock causes the rock to weaken until it breaks apart. The loose broken rock is called scree. When the scree collects at the bottom it is known as a scree slope. Also on a gentler slope the scree forms a Block Field as the scree cannot roll away.
  7. 7. Freeze Thaw Weathering Freeze thaw weathering affects Granite as it is an impermeable (resistant to water) rock. The features caused by freeze thaw weathering on granite include Tors, which are large standing blocks, scree and outcrops of granite. An example of a granite area which is affected by freeze thaw weathering is Dartmoor, located in Devon in South West England.
  8. 8. Freeze Thaw Weathering Tors form when, firstly lava cools and solidifies causing joints (vertical cracks) to form in the surface. Freeze thaw weathering attacks the joints in the Granite. When the joints are closer together the weathering affects the granite more.
  9. 9. Freeze Thaw Weathering Over time rock becomes gradually more weathered and large gaps appear in the rock the rock in between the spaces are the tors. There is usually scree around the base of the tor as the weathered rock falls to the bottom of the rock face to form a scree slope. Cheesewring tor Dartmoor
  10. 10. Solution Weathering An example of a limestone area where solution weathering occurs would be Malham Solution weathering occurs when the water is slightly acidic and the rock is slowly dissolved by the water, the type of rock which is affected by this type of weathering is is limestone as it is a pervious rock meaning that water can flow through the joints and bedding planes. The formula for this process is: CaCO 3 +H 2 O Ca(HCO 3 ) 2
  11. 11. Solution Weathering There are many features formed by solution weathering on limestone, these include limestone pavements, which form when solution weathering causes weakness in the rock to form grykes (gaps in the rocks) and clints. Other formations include caverns which form when the acidic water flows down the joints and bedding planes. Then these are eventually eroded to form caverns.

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