Weathering and erosion

1. Define ‘weathering’.
2. Define ‘erosion’.

Carbonation

Carbonation is the process in which atmospheric carbon dioxide leads to solution weathering. Carbonation occurs on rocks which contain calcium carbonate such as limestone and chalk. Carbonation takes place when rain combines with carbon dioxide to form a weak carbonic acid which reacts with calcium carbonate (the limestone) and forms calcium bicarbonate.

This process speeds up with a decrease in temperature and therefore is a large feature of glacial weathering as carbon dioxide is more soluble at lower as opposed to higher temperatures.

The reactions as follows:

CO₂ + H₂O → H₂CO₃
carbon dioxide + water → carbonic acid

H₂CO₃ + CaCO₃ → Ca(HCO₃)₂
carbonic acid + calcium carbonate → calcium bicarbonate

Oxidation

Within the weathering environment chemical oxidation of a variety of metals occurs. The most commonly observed is the oxidation of Fe²⁺ (iron) and combination with oxygen and water to form Fe³⁺ hydroxides and oxides such as goethite, limonite, and hematite. This gives the affected rocks a reddish-brown coloration on the surface which crumbles easily and weakens the rock.

This process is better known as 'rusting'.

Physical weathering

3. Describe the weathering process that is happening in the image above, in as much detail as possible.

Chemical weathering

4. Describe the weathering process that is happening in the image above, in as much detail as possible.

Biological weathering

5. Describe the weathering process that is happening in the image above, in as much detail as possible.
6. Why is freeze-thaw weathering more common in highlands?
7. Why is exfoliation more common in desert areas?
8. Why is the rate of chemical weathering often greater in industrial areas?
9. What is the difference between weathering and erosion?