Minerals present in rocks undergo changes because of the action of water, oxygen, and other organic acids. Thus, rocks get decomposed because of chemical weathering. This happens because of chemical reactions which occur in rocks when these agents come into contact with the surface of rocks. There are four types of chemical weathering:
Types of chemical weathering
Solution
- Minerals present in rocks get dissolved in water. The rate at which the solution of rocks takes place is subject to the chemical composition and the structure of rocks.
- For example, rainwater causes chemical disintegration of gypsum.
Carbonation
- Many rocks contain constituents that have carbon dioxide present in them. When it comes in contact with water, acidic effects on rocks are produced.
- Many rocks such as marble and limestone get dissolved in water. Rainwater converts carbonate into calcium bicarbonate which is soluble and hence dissolves in water.
Oxidation
- Minerals present in rocks react with oxygen present in the atmosphere. Rainwater also involves atmospheric oxygen.
- When rainwater comes into contact with the iron compounds in rocks, iron begins to rust. This may also change the colour of the rocks to red, brown or yellow.
Hydration
- Minerals present in rocks expand on coming into contact with rainwater.
- The minerals become heavy and begin to break down. Rocks such as feldspar get converted to kaolin.
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