The four main types of weathering include freeze-thaw, exfoliation, chemical and biological weathering. Weathering involves the process of rock breaking down into soil via various physical, biological and chemical reactions.
The freeze-thaw method of weathering takes place when water penetrates small cracks in the rock and then freezes. When the water freezes, it expands, causing the crack in the rock to be placed under pressure and expand. The ending result is a break in the rock. The broken rock pieces can then break down further in the weathering process.
Exfoliation, also called onion skin weathering, involves the dramatic temperature changes on the rock. During the day, the rock is exposed to elevated temperatures, and at night, the rock is subjected to much cooler temperatures. This effect over an extended period of time results in a "flaking" effect on the rock.
Chemical weathering can take place in a rock when water, which seeps into the rock, contains amounts of acid, causing a chemical breakdown of the rock. This especially affects limestone, and it can be seen on buildings and other structures that are built with limestone rock.
Biological weathering involves effects from a living organism, such as a tree or moss. Tree roots can break rocks apart, and moss can break down the surface of a rock over a longer period of time.