Chemical Weathering of Rocks
The formation of new compounds in the rocks due to chemical change is called chemical weathering.
Chemical processes include oxidation, hydrolysis, and an acid solution.
Chemical weathering involves four major processes:
In this process atmospheric oxygen reacts with the rock to produce oxides.
The process is called oxidation.
The greatest impact of this process is observed on ferrous minerals.
Humid-air oxygen combines with iron grains in the rocks to create a yellow or red iron oxide.
This is called rusting of the iron.
Rust decomposes rocks completely with the passage of time.
This is the process by which various types of carbonates are formed.
Some of these carbonates are soluble in water.
For example, when rainwater containing carbon dioxide passes through limestone rocks, the rock joints enlarge due to the action of carbonic acid.
Joints are expanded and lime is dissolved in solution.
This form of rock breakdown is called carbonation.
This is the process by which water is absorbed by the minerals of the rock.
The volume increases due to the absorption of water by the rock, and the grains lose their structure.
For example, the feldspar is converted into kaolin by hydration.
Kaolin on Vindhyan Hills near Jabalpur has been formed in this manner.
This is the process in which some of the minerals get dissolved in water.
They are therefore removed in solution.
Rock salt and gypsum are removed by this process.