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Chemical weathering takes place when water, oxygen, carbon dioxide, and other chemical substances react with rock to change its composition. These reactions convert some of the original primary minerals in the rock to secondary minerals, remove other substances as solutes, and leave the most stable minerals as a chemically unchanged resistate .
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 ...
Clay minerals most commonly form by prolonged chemical weathering of silicate-bearing rocks. They can also form locally from hydrothermal activity. [ 16 ] Chemical weathering takes place largely by acid hydrolysis due to low concentrations of carbonic acid , dissolved in rainwater or released by plant roots.
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. [ 50 ] [ 51 ] As demonstrated in the following reaction, this causes potassium feldspar to form kaolinite , with potassium ions, bicarbonate, and silica in solution as byproducts.
Many explanations have been proposed for honeycomb and other cavernous weathering. These explanations include marine abrasion; wind corrosion; mechanical weathering resulting from short-term temperature variations; chemical weathering of the interior of the rock (core-softening) under a protective crust (case-hardening) followed by mechanical removal of the softened material; biogeochemical ...
Biological weathering is a form of weathering (mechanical or chemical) by plants, fungi, or other living organisms. [12] Chemical weathering can happen by different mechanisms, depending mainly on the nature of the minerals involved. This includes solution, hydration, hydrolysis, and oxidation weathering. [13]
Chemical weathering of igneous minerals leads to the formation of secondary minerals, which constitute the weathering products of the parent minerals. Secondary weathering minerals of igneous rocks can be classified mainly as iron oxides, salts, and phyllosilicates. The chemistry of the secondary minerals is controlled in part by the chemistry ...
Spheroidal weathering of a dolerite dyke, Pilbara, Western Australia. Spheroidal weathering is a form of chemical weathering that affects jointed bedrock and results in the formation of concentric or spherical layers of highly decayed rock within weathered bedrock that is known as saprolite.