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In this article we are discussing the types of chemical weathering processes.
B) Carbonation :
i) Carbonation is the reaction of carbonate & bicarbonate with minerals. It is a common process that helps feldspars & carbonate minerals to disintegrate.
ii) Carbonic acid is formed due to absorption of carbon dioxide from the atmosphere, soil and air into water. It acts as a weak acid.
iii) Calcium carbonates & magnesium carbonates are dissolved in carbonic acid and removed in a solution without leaving any residue. This process of carbonation results in cave formation.
C) Hydration:
i) Hydration is the chemical addition of water in minerals.
ii) Minerals take up water and expand themselves, thereby increasing the volume of the resultant material or the rock.
iii) For example, calcium sulphite absorbs water and turns into gypsum, which is more unstable than calcium sulphite. This process is reversible & long.
iv) Nonstop hydration can cause fatigue in rocks and may lead to their disintegration.
v) Many clay minerals show the same tendency and result in cracking of overlying materials.
vi) Salts in pore spaces undergo rapid & repeated hydration that causes rock fracturing (cracks that divide rocks into pieces).
vii) Volume changes in the rock also lead to physical weathering through exfoliation & granular disintegration.
D) Oxidation & Reduction:
i) The process of combination of a mineral with oxygen to form oxides or hydroxides is called oxidation.
ii) It occurs when rocks are exposed to atmospheric oxygen or oxygenated water. Rocks break down due to disturbance caused by addition of oxygen.
iii) Iron, manganese, sulphur, etc are minerals commonly involved in this process. Due to oxidation of iron, it turns from red to yellow or brown.
iv) The process of reduction occurs when oxidised minerals are exposed to an environment where oxygen is absent. Such conditions exists below the water table, in stagnated water or water-clogged ground.
v) Reduction changes the red colour of iron into greenish or bluish grey.
To learn about previous articles on Geomorphic processes click here :
a) Geomorphic Processes 1
b) Geomorphic Processes 2
c) Geomorphic Processes 3
d) Geomorphic Processes 4
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