chemical weathering

The reddish-orange color of this oxisol soil shows is a 
result of oxidation, a chemical weathering process.
(Courtesy: NRCS)

Chemical weathering is the chemical decomposition of geological material (e.g., rocks, soil parent material) by a variety of chemical process like oxidation, hydrolysis, and carbonation. Chemical weathering alters the chemistry of the weathered material, whereas physical weathering does not.