Chemical weathering is the breakdown of rocks due to the processes of hydration, solution, oxidation and carbonation. Rain water combines with carbon dioxide (CO2 ) to form the weak carbonic acid. Under the attack of such acidic rain water, most rock minerals will be weathered. The process is accelerated by high temperature so that it is more active in hot and wet conditions.
(a) Spheroidal weathering - This occurs mostly in granitic area under hot and wet climate. Granite is well- jointed and contains feldspar which can be easily decomposed. The rain water can seep into the rocks and decompose them along the joints, ie, the outer layer of the rocks.
As the outer layers are weathered, they peel off and leave behind a rectangular block which will be rounded off eventually. When the weathered materials are moved away, the corestones are exposed to form tors.
(b) Honeycomb weathering - Sea spray and rain water can dissolve the soluble minerals in the rocks. The removal of such minerals forms a honeycomb feature on the rock surface.
Biological weathering Plants and animals may help in the breakdown of rocks as shown in the diagram below.
