Word count: 1643 Panuma Rai 'Outline the main weathering processes and discuss the factors that control their operation.' Introduction Weathering is one of the essential subjects when talking about the earth's processes. Weathering is the disintegration of rocks and minerals at the earth's surface; it can be caused by heavy rainfall or extreme fluctuation of temperatures. There are three main types of weathering; mechanical or physical, biological and chemical weathering. Mechanical weathering is gradual breakdown of rocks into smaller fragments. There are six main types of processes for mechanical weathering; unloading, frost action, heating and cooling, wetting and drying and salt crystal growth. (John Huggett, R., 2011) Chemical weathering is when chemical reactions occur with different types of rocks in certain climatic conditions. There are six main types processes of chemical weathering; Solution, hydration, oxidation, oxidation, reduction, carbonation and hydrolysis. (John Huggett, R., 2011) Biological weathering is mechanical, chemical or even combination of both processes that breakdown rocks. An example of this can be rocks being broken by plant roots or moss. (John Huggett, R., 2011) There are a lot of factors which can control weathering operation such as their rate and extent of weathering. These factors can be due to the climate, rock type, rock structure, topography, erosion and time (Hong Kong Geological, 2009). Discussion Mechanical or Physical weathering Mechanical weathering is the breakdown of rocks and minerals by mechanical methods that is caused by many processes. It's the gradual breakdown of rocks into small pieces due to strain and rupture.
Word count: 1643 Panuma Rai When there is a tectonic uplift and erosion of overlaying rocks the pressure confined is released and the pressure underneath the rock will exert, forcing the rock to expand. This process is referred as unloading (Pidwirny, M. (2006). Exfoliation is a process of the earth's surface rocks peeling into fragments due to unloading. This process can create landforms called exfoliation domes such as Half dome in Yosemite national Park (John Huggett, R., 2011). Frost action occurs when water seeps through the pores within rocks and soil, expanding 9 percent when freezing (John Huggett, R., 2011). This causes stress as it expands in the pores causing the rock to break. Frost shattering is when small pieces or big boulders of rock are broken off to make into even smaller fragments. This type of process is common in cold environments where freeze thaw cycles are most dominant. Hydrofracture occurs when unfrozen water is trapped underneath the frozen water moisture at the surface of the pores sealing of the end of the soil/rock (Whalley. W, Warke, P, 2005). The expanding ice will increase the hydrostatic pressure and transfer the force into the hollow space of the unfrozen water making it able to shatter rocks. Thermal fatigue occurs due to rocks having low conductivities. By continuous heating and cooling can lead to disintegration of the rock as there is different level of expansion (Whalley. W, Warke, P, 2005) .. This produces a fatigue effect at the surface