Earth Sciences 1022A/B Lecture Notes - Lecture 5: Hydrolysis, Pedogenesis, Silicate Minerals
10 Jan 2017
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Document Summary
After rocks are formed, they are weathered when expressed at the surface; this prepares material for transport by erosional processes in the rock cycle. These act together and enhance the effectiveness of each other: mechanical (disintegration) Breaking up rock into smaller pieces, providing more surfaces for chemical attack. Frost wedging happens through ice forming (water expanding by 9%) in cracks in rocks, breaking them apart. Sheeting/unloading due to expansion on removal of overlying material. Biologic activity plant roots grow in rock fractures and pry the fractures open: chemical (decomposition) Dissolution water in the weathering zone is weak carbonic acid that reacts with most minerals, turns them into substances stable at surface conditions. Oxidation dark silicates react with oxygen to form rusty fe, mg oxides and clay minerals. Hydrolysis orthoclase in granite changes to clay by exchanging k+ for tiny h+ ions. Rates of weathering depend on how fractured rock is, types of minerals, climate.
