Weathering chemical changes

Weathering All physical and chemical changes produced in rock by atmospheric agents. 

The weathering process which eventually reduces the rock of the parent material to the inorganic constituents of soil comprises both physical and chemical changes. Size reduction from rocks to the colloidal state depends not only upon the mechanical action of natural forces but also on chemical solubilisation of certain minerals, action of plant roots, and the effects of organic substances formed by biological activity. 

Hydration is the incorporation of water mole-cule(s) into a mineral, which results in a structural as well as chemical change. This can drastically weaken the stability of a mineral, and make it very susceptible to other forms of chemical weathering. For example, hydration of anhydrite results in the formation of gypsum ... 

Phase transitions, although rarely described in these terms represent the second example of chemical change in the local environment. The most familiar example is transformation between the phases of water, which is responsible for all observed climatic and weather changes on the planet. Volcanic activity is another dramatic manifestation of phase transformations. 

Freyssinet, Ph., Piantone, P., Azaroual, M., Itard, Y., Clozei.-Leloup, B., Guyonnet, D. Baubron, J. C. 2002. Chemical changes and leachate mass balance of municipal solid waste bottom ash submitted to weathering. Waste Management, 22, 159-172. 

Weathering produces physical as well as chemical changes. Miniutti, in a series of papers, examined microscopic changes in cell structure of softwood surfaces during weathering and ultraviolet irradiation (21-25). 

The cracks steadily increase in number and size. The chemical changes add to the roughness and soften the surface of the board (9,25). In addition to the minute checks on the surface, most woods soon develop larger and deeper checks or cracks that are easily visible. As the weathering process continues, boards tend to cup, warp, and pull at their fastenings (50. Woods of moderate-to-low density acquire fewer checks than do woods of high density. 

The chemical changes occurring and the mechanisms of degradation and color formation during weathering have received considerable attention and have been summarized in an earlier paper in this series (3). 

Physical weathering rocks are fragmented little or no chemical changes plays a role in rugged topography and special climates. 

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