Chemical Weathering

The decomposition of rocks by different types of chemical processes is known as chemical weathering. In order to understand the concept of chemical weathering one should understand what is meant by the term weathering. Weathering describes the combined action of all processes that cause rock to disintegrate physically and decompose chemically because of exposure near the earth’s surface. (Strahler 2010). Weathering can be split into two categories, physical weathering and chemical weathering. Physical weathering occurs when rocks are fractured. Chemical weathering is the alteration of the composition of the rocks where water is the dominant agent. The following will describe the agents and processes involved in chemical decomposition of rocks or chemical weathering. As well as identify which process will erode a terrain composed mainly of limestone most effectively with a detailed explanation for the chosen process.

Chemical weathering can be subdivided into several different processes which include hydration, hydrolysis, oxidation and reduction, carbonation and complexation. In the presence of water ions become hydrated and thus dissociates. In more simplistic terms hydration is the process by which rocks absorbs water and usually occurs in arid areas where salt is present. When the water is absorbed the chemical change occurs increasing the size of the rock. It is this swelling that stresses the rock and leads to rock deformation, flaking and colour changes. An example of hydration would be the absorption of water by an anhydrite and as a result gypsum is formed.

Another process of chemical weathering is hydrolysis which entails the exchange of minerals and water. Water changes the chemical composition and size of the minerals in rocks making it less resistant to weathering. The exchange is brought about by free hydrogen and hydroxide ions in water and mineral solutions. A suitable example of this would be the hydrolysis reaction of feldspar...