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Physical weathering, also called mechanical weathering or disaggregation, is the class of processes that causes the disintegration of rocks without chemical change. Physical weathering involves the breakdown of rocks into smaller fragments through processes such as expansion and contraction, mainly due to temperature changes.
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The regolith of a region is the product of its long weathering history; leaching and dispersion are dominant during the initial phase of weathering under humid conditions. [1] Saprolites form in high rainfall regions which result in chemical weathering and are characterised by distinct decomposition of the parent rock's mineralogy. [5]
The difference in chemical weathering time can span millions of years. For example, quickest to weather of the common igneous minerals is apatite, which reaches complete weathering in an average of 10 5.48 years, and slowest to weather is quartz, which weathers fully in 10 8.59 years. [5]
Tropical weathering (laterization) is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils. [10]: 3 The initial products of weathering are essentially kaolinized rocks called saprolites. [11]
Chemical weathering of feldspars happens by hydrolysis and produces clay minerals, including illite, smectite, and kaolinite. Hydrolysis of feldspars begins with the feldspar dissolving in water, which happens best in acidic or basic solutions and less well in neutral ones. [ 30 ]
Chemical weathering of granite occurs when dilute carbonic acid, and other acids present in rain and soil waters, alter feldspar in a process called hydrolysis. [ 49 ] [ 50 ] As demonstrated in the following reaction, this causes potassium feldspar to form kaolinite , with potassium ions, bicarbonate, and silica in solution as byproducts.
The rate of weathering is sensitive to factors that change how much land is exposed. These factors include sea level , topography , lithology , and vegetation changes. [ 4 ] Furthermore, these geomorphic and chemical changes have worked in tandem with solar forcing, whether due to orbital changes or stellar evolution, to determine the global ...