Chemical weathering is caused by chemical changes, when rock is dissolved or decays.
Carbonation Carbonation is an example of chemical weathering.
CO2
Rainwater + CO2
= weak carbonic acid
Limestone
Bedding plane Joint
The calcium carbonate in limestone dissolves in the same way as when you drop soluble tablets into water!
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As rainwater falls and passes through the air, it dissolves carbon dioxide. Carbon dioxide mixes with the rainwater to form a weak carbonic acid.
Limestone in the ground contains calcium carbonate. When the weak carbonic acid in the rainwater falls onto the limestone, a chemical reaction takes place.
The calcium carbonate in the limestone begins to dissolve. This process is known as carbonation.
Limestone is a permeable rock, which means that rainwater can easily pass through it. It has vertical cracks, which are known as joints, and horizontal bedding planes.
Karst landscapes
Karst landscapes are areas of land made up of limestone. The effects of carbonation are best seen in karst areas. The overlying soil and plants have been removed, and the bare limestone rock is exposed (uncovered). An example of a karst region in Ireland is the Burren in County Clare.
