What are the different types of weathering?
There are four main types of weathering. These are freeze-thaw, onion skin (exfoliation), chemical and biological weathering.
Freeze-Thaw
Most rocks are very hard. However, a very small amount of water can cause them to break. When water seeps into cracks and freezes it then expands. This powerful force can increase the size of cracks. Over time the repeated freeze-thaw action of water can break rocks apart. Eventually, pieces of rock break off creating scree.
Image 1 below shows the impact of freeze thaw on a rock in Iceland.
Exfoliation or Onion Skin Weathering
This type of erosion is common in warm areas. As the sun shines on rocks during the day it causes them to expand. During the night the rock contracts due to the colder temperature. Over time this continued process causes small pieces of surface rock to flake off.
Images 2 and 3 below shows a close up of onion skin weathering.
Chemical Weathering
Chemical weathering causes an alteration to the chemical composition of rock due to a reaction. Water that is slightly acidic can disolve rock. An example of this would be slightly acidic rain changing the chemical composition of limestone to form a limestone pavement. This occurs on the surface and along the joints and bedding planes of limestone. You can also see evidence of this on buidlings made from limestone.
The resulting formation is known as a limestone pavement. You can find out more about these in the limestone geotopic.
Images 4 and 5 below shows a cases of chemical weathering.
Biological Weathering
Biological weathering is the effect of living things. For example as the roots of a tree extend into the ground they can prise rocks apart. Ivy growing up a building can cause bricks to loosen. It also occurs on a much smaller scale through lichen and moss.
Image 6 below shows how this tree will cause weathering.
Please answer these easy questions and remember to submit then in order to validate your find:
1. What type of weathering would you identify at GZ by looking at the surrounding landscape?
2. In two sentences explain your answer in question1.
3. Do you think there might be any other type of weathering occurring based on what you see here?