Weathering

The rate of weathering is also affected by various factors such as climate, geology, relief, soil or vegetation cover, as well as human activity. Research studies regarding the causes and effects of weathering continues and play a vital role in understanding the history of earth movement and development. Weathering is defined as group of slow processes by which surface rocks are broken into smaller pieces or dissolve into water as caused by the impact of the atmosphere and hydrosphere. It is considered as the primary stage in the denudation of the landscape since rocks are loosened by the weathering process. The length of time that rocks and minerals have been exposed at the surface of the earth will dictate the degree to which they have weathered. Pushkar (799) explained the process of weathering: Soils are derived from the parent rocks by the process called weathering. Formation of soil is initiated by disintegration or weathering of parent rocks by certain physical, chemical or biological agents. As a result, soil-forming rocks are broken down into small particles called regoliths, which finally develop into mature soil by pedogenesis. After the loosened rock particle moves due to flowing agents specifically air, water or ice, erosion or mass wasting occurs. Erosion refers to the movement down slope due to gravity (US Geological Survey National Park Service). Physical weathering or mechanical weathering is a type of weathering in which the breakdown of rock relies solely through mechanical forces such as freeze thaw, pressure release, thermal expansion, salt crystallization, sand blast, and glaciation, which do not alter the chemical composition of the rock. Freeze thaw refers to the breakdown of rocks as a result of the expansion of water during freezing which is common in places where temperature often fluctuates around zero degrees Celsius like in upland Britain. This procedure is most effective in jointed rocks particularly granite. Pressure release or dilation happens when weathering and erosion removes overlying rocks. The released pressure expands the rocks, making it to have fractures which weaken the rocks as they become susceptible to weathering agents. Sheeting of rock follows when cracks develop parallel to the surface. Thermal expansion, also called as insolation weathering, results from large diurnal temperature ranges that influences heating and cooling of the rock. The rock expands when heated and contracts when cooled. The changes caused by differing temperature results in stresses in the rock layers. Salt crystallization takes place when saline water passes through crevasses and joints in rocks, evaporates, and salt crystals are formed as the dissolved salts crystallize. The crystals can cause granular disintegration or the gradual breaking off grains of rock. Sand blast occurs in arid and desert conditions when wind and sand disrupts rocks. Lastly, glaciation or ice formation corrodes and breakdown rocks into sand particles as the melting of ice during summer season move downwardly on the slopes and produces glacier movement (Codrington 252). On the other hand, chemical weathering is defined as the decomposition of a rock by alteration of its chemical composition (Codrington 252). The processes of chemical weathering are solution, hydrolysis, chelation, hydration, carbonation and oxidation-reduction. Solution involves the removal of certain mobile components of rocks for instance, calcium sulphates and chlorides, making the rocks porous and easy to disintegrate. Hydrolysis breaks down or washes out components of rocks such as alumina silicates and silicon which leads to simpler mineral matter like