Earth Sciences 1022A/B Lecture Notes - Regolith, Orthoclase, Parent Material
5 Dec 2013
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Breaking up rock into smaller pieces, providing more surfaces fro chemical attack. Frost wedging: water freezes in rock fractures and expands 9%, prying rock apart. Unloading: rock surface expands after stuff on top is removed, slabs break off. Biologic activity: plant roots grow in rock fractures and pry the fractures open. Dissolution: co2 dissolves in water to make weak carbonic acid that dissolves rock minerals. Oxidation: dark silicates react with oxygen; form fe, mg oxides, clays. Hydrolysis: orthoclase in granite changes to clay by exchanging large k+ ions for tiny h+ Light silicates form closer to weathering conditions, more stable; marble is soluble, unstable. Dark silicates form under higher p, t conditions, unstable under weathering conditions. Climate: weathering is greater in warm, wet climates. Biologic activity combined with weathering (produces regolith without biologic input); added organics are called humas. Parent material: rock or sediment on which soil forms. Rills become gullies, which join to form streams and remove soil.
