Earth Sciences 1022A/B Lecture Notes - Lecture 11: Silicate Minerals, Clay Minerals, Orthoclase
14 Apr 2015
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Earth sciences 1022b lecture brief 22 jan 15. After rocks are formed, they are weathered when exposed at the surface; this prepares material for transport by erosional processes in the rock cycle. Two main types of weathering include mechanical (disintegration) and chemical (decomposition) that act together and enhance the effectiveness of each other. Mechanical: reduction of rocks to smaller pieces, includes: frost wedging by ice forming in cracks in rocks, breaking them apart; sheeting due to expansion on removal of overlying material; biologic activity - roots open fractures. E eluviated (downward-transported) fines and leaching of ions in solution. B accumulation of oxides and clays (in wet climates) Soil erosion: serious problem worldwide; we need soils for food production. Starts with raindrops displacing soil particles then sheet erosion washes them into rills, gullies, and eventually to streams that carry the soil away; accelerated by deforestation by farming, logging, construction etc plants anchor, protect topsoil.
