Weathering - Research Paper Example

Weathering Weathering, or “the process of breaking down a rock” (Codrington 252), is an important geological process that initiates soil formation aside from mineralization and humification and organo-mineral complex formation. Often confused with erosion by lay persons, weathering can be classified into physical, chemical and biological. 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 clay alumina-silicates. Chelation refers to the dissolution of metals with chelates or the organic products of microbial activities. The chemical exudates produced by biochemical activities of microorganisms, lichens, bacteria and cyanobacteria liquefy the mineral components of the rocks. The third type of weathering, biological weathering, entails a combination of physical and chemical processes. Biological weathering may be caused by tree roots, animal activity and organic acids. Tree roots often go in and exploit crack joints in rock as they grow downwards. Their invasion causes detachment of rock fragments similar to freeze thaw. Animal activity such as burrowing helps in opening up joints in rock as well as bringing rock fragments to the surface. Organic acids are released into the ground as roots decays. When aided by percolating rainwater, organic acids may react with minerals in the rock through chelation (Pushkar 799). The processes of weathering depend mainly on certain climatic situations which determine temperature and the availability of water. The significance of climate as a factor affecting the rate of weathering has been studied by White and Blum (1729), in which the importance of water and temperature in both chemical and physical weathering are underscored. It was observed that freeze-thaw and thermal expansion are more effective when there are large daytime ranges in temperature. Thermal expansion is also suitable in deserts and arid environment. In addition, chemical weathering is limited in cold, dry locations but ineffective in very low temperatures. Because of the strong influence of climate on weathering, Peltier diagram was created to calculate the weathering rates in a specific location using the annual temperature and rainfall as shown in the diagram below. Moreover, scientists believe that weathering will rapidly increase in the coming years. Temperature will dramatically increase as the sun ages since the maturity of the sun makes it brighter (Overbye 2011). Nevertheless, weathering is a natural process that mainly impacts the formation of soil and its aggregates. It is critical to understand the classes of weathering and the factors affecting it in order to fully grasp the developments behind the phenomenon and to possibly predict the geological trends in the future. Works Cited Codrington, Stephen. Planet Geography. Solid Star Press. 2005. Print. Overbye, Dennis. “Hot on Trail of Just Right Far-Off Planet.” The New York Times. 2 Dec. 2011. Web. 1 Nov. 2012. Pushkar, Kumar. “Edaphic Factors: Soil Composition and Formation.” Competition Science Vision Magazine. Aug 2003. Web. 31 Nov. 2012. US Geological Survey National Park Service. “What’s the difference between weathering and erosion?” US Geological Survey National Park Service Website. n.d. Web. 31 Nov. 2012. White, Art F. and Blum, Alex E. "Effects of Climate on Chemical Weathering in Watersheds". US Geological Survey. 59.9 (1995): 1729-1747. Print. Read More