Answer:
oxidation
Step-by-step explanation:
oxidation is a chemical weathering process whereby the iron compounds in the rock react with the oxygen in the air to produce a reddish brown coating.
it occurs only on rocks that contain iron for example sandstone. the dissolved oxygen in both the soil and air react with the iron minerals in rocks to oxidize and become iron oxide and the iron becomes rust forming the red color. iron oxide either remains in the soil or rocks as reddish brown coating or in waterlogged areas it can be removed in solution.
the chemical process for oxidation is FeO=Fe2O3