Weathering is the natural decaying or wasting of rocks, soils and their minerals at or near the surface of the earth. Weathering breaks down and loosens the surface minerals of rock so they can be transported away by agents of erosion such as water, wind and ice. It eventually converts the rocks into sand, clay, and dissolved salts. All soil is derived from weathered materials, a soil weathered from a mix of different rock types often makes a more fertile soil.

The rate at which weathering occurs depends a great deal on the climate, an exposed big stone in a desert typically show little chemical weathering, whereas exposed big stones in a rain forest are often so weathered that they will crumble under a single blow.

Weathering is classified as:

• Chemical weathering - involves chemical reactions that decompose the minerals that make up a rock, it therefore transforms the original material into a substance with a different composition and physical characteristics. Chemical weathering is caused primarily by exposure of the material to water, air and rainfall. Rainfall is slightly acid because the carbon dioxide in the atmosphere dissolved in it, producing a weak carbonic acid.

The rate of chemical weathering is greatly accelerated by the presence of warm temperatures and moisture. CW affects different minerals in different ways, example is feldspar mineral, this mineral partially dissolves overtime, leaving only a clay residue. Another one is limestone, it dissolve completely and are carried away by flowing water. Quartz is resistant to chemical weathering, the grains of quartz from the weathered rock generally remain intact and are deposited as particles of sand. Types of chemical weathering includes; dissolution, hydrolysis and oxidation.

• Physical weathering - involves the breakdown of rocks and soil through direct contact with heat, water, ice and pressure. One of the main causes of physical weathering is the freezing of water in small cracks in rocks. As the water freezes, it expands, causing the rock to fracture. When rock is broken into pieces, the amount of exposed rock increases, which in turn accelerates chemical weathering. Types of physical weathering include; frost wedging, exfoliation and thermal expansion.