Earth Sciences 1022A/B Lecture Notes - Lecture 4: Ice Crystals, Humus, Hydrolysis
14 Apr 2016
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Es 1022b- lecture 4- part 2- weathering soils. Water freeing in rock fractures, expands 9% prying rock apart. Ice crystals in between and spreads the fracture walls. Eventually the fracture is too big and breaks rock, talus fragments. Rock surface expands after stuff on top is removed slabs break off. 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. Rock characteristics: light silicates form closer to weathering conditions, more stable; marble is soluble, unstable, dark silicates form under high 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 humus.
