Rust on rocks weathered by oxidation.
As rocks and minerals shift and move from the Earth's womb to the surface, the subjection of the surface environment that causes the breakdown and alteration of these rocks and minerals results in weathering. A springboard for other geomorphic and biochemical processes, weathering provides an important impact on the Earth's surface. Chemical weathering, in particular, causes changes in the chemical and mineralogical make up of different materials. Essential environmental factors for weathering lie in temperature and climate.
Hydrolysis
Hydrolysis, according to the "Encyclopedia of Earth," happens when water and rocks and minerals meet. The reaction that occurs between the two forms a solution that decomposes the original material. In this process, new compounds form and pH increases through the release of hydroxide ions. Silicate and aluminosilicate minerals prove especially susceptible to this cause of chemical weathering due to the presence of electrically charged crystal exteriors. When the silicate mineral, potassium feldspar, undergoes hydrolysis, it forms into a clay mineral.
Oxidation
Another cause of chemical weathering, oxidation transpires between compounds and oxygen. According to the University of Wisconsin Department of Geology and Geography, oxygen dissolved in water then combines with metallic elements. The formation of rust in red to brownish streaks on materials denotes the one outcome of oxidation. As oxygen reacts and combines with iron, it becomes the iron oxide hematite.
Hydration
Like hydrolysis, hydration involves water. However, instead of forming a solution, materials absorb the water and then create a new product. An example of hydration occurs when the ions H+ and OH- attach to hematite materials and change them to limonite. In addition, according to the "Encyclopedia of Earth," hydration can accelerate other weathering reactions by expanding the crystal lattice of materials to allow for a wider surface area to form and become subject to decomposing.
Carbonation
The causation of chemical weathering through the process of carbonation happens when carbonate and bicarbonate ions react with minerals and produce a new product. Often, other chemical processes encourage the development of a carbonate reaction due to formation of additional carbonates.
Also, environments high in carbon dioxide encourage this process to take place, as the existence of carbonic acid has a huge impact on the decomposition of rocks and minerals. Rainwater, for instance, mixes with carbon dioxide in the atmosphere to form carbonic acid that then fall to the Earth to mix and react with materials found there. According to the University of Wisconsin Department of Geology and Geography, as carbonic acid comes into contact with calcite, a mineral found in limestone, the resulting chemical reaction causes calcium and bicarbonate ions to separate.
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