The breakdown of rocks into smaller pieces is called weathering. Weathering can occur through either mechanical or chemical processes. One agent of chemical weathering is oxidation. This form of weathering is referred to as oxidation weathering. Oxidation is the reaction of a substance with oxygen. Oxidation changes the molecular composition of the substance. For example, iron in rocks undergoes oxidation to form iron oxide. Iron oxide is commonly known as “rust”. Iron oxide is brittle and crumbles easily, thus causing the rock to weather and break apart into smaller pieces.
Carbonation and hydrolysis are two other forms of chemical weathering.
Agents of mechanical weathering include wind, ice wedging, the expansion and contraction of rocks as a result of temperature changes, the burrowing of animals, or the uplifting of rock by the roots of plants.