Weathering in general refers to a group of processes by which surface rocks disintegrates in-situ into smaller particles or dissolve into water due to the impact of the atmosphere and hydrosphere. According to Waugh weathering is the first stage in denudation or wearing down of the landscape; it loosens material which can subsequently be transported by such agents of erosion as running water, ice, the sea and the wind. However it should be noted that no transportation of the weathered material (regolith) is involved. Weathering processes are often slow, taking hundreds to thousands of years. The amount of time that rocks and minerals have been exposed at the earth's surface will influence the degree to which they have weathered as well as the structure and mineral composition of the rocks, local climate and vegetation. Furthermore, decomposition and disintegration are interacting processes. For example, disintegration greatly promotes decomposition by reducing large intact rock masses to accumulations of smaller fragments. This fragmentation provides more total surface area for chemical attack than was originally present in the larger mass of rock.
Weathering processes are divided into three categories namely physical, chemical and biological weathering. In this essay the agents and processes involved in the chemical decomposition of rocks would be examined. The process of chemical weathering generally occurs in the soil where water and minerals are in constant contact. Agents of weathering are oxygen, air pollution, water, carbonic acid, and strong acids with water as the dominant agent. They combine with the minerals in rocks to form clays, iron oxides, and salts, which are the endpoints of chemical weathering. This weathering is more likely to take place in warmer, moister climates where there is an associated vegetation cover. Moreover, chemical weathering processes include hydration, hydrolysis, oxidation/reduction, complexation and carbonation.