> THE KARST – Chemical and hollowing out processes
The hollowing out process
Both hollowing out and the surface erosion of limestone rock can occur from both mechanical and chemical processes.
> Chemical processes occur when carbonates, the constituents of limestone, are dissolved by water enriched with carbon dioxide.
> Mechanical processes, mainly caused by the movement of water, both on the surface and inside the rocks, are of two kinds:
The environment and climatic conditions that govern the amount of precipitation; and factors associated with the rock itself or how it was deposited such as cohesion and porosity, caused by the internal structure of the rock. These influence the speed and flow of water.
Movements of the earth that cause rocks to fold and break up, which influence the direction and shape of the water flows.
The chemical process
Carbon dioxide dissolves in water, and some combines with it to form carbonic acid (H2 CO3). Carbonic acid reacts with the calcium carbonate in the limestone to form a soluble compound - calcium bicarbonate.
The bicarbonate is dissolved and taken away by the water. This leaves an empty space, and any residues are caused by impurities in the rock.
This process is caused by a chemical reaction which is expressed as follows: |