A9R18EC.tmp 22 - : fracturing into thin slabs of rock...

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Prof. M. Fall - University of Ottawa 22 4.1 Weathering of materials There two main categories of weathering of the materials of the earth’s crust : Physical weathering Chemical weathering weathering = in-situ disintegration or decomposition of the rock 4 Weathering and erosion Physical weathering Chemical weathering Phenomena occur simultaneously in general Predominance controlled by the climate Physical weathering increases the specific surface of the materials thereby making easier the actions of chemical weathering 4.1 Weathering of materials 4 Weathering and erosion Climate and weathering 0 o F = -17.7 o C 4.1 Weathering of materials 4 Weathering and erosion Physical weathering The main agents of physical weathering are: The main agents of physical weathering are: Temperature changes changes : : Cycle of freeze/thaw, differential temperature (thermal expansion) expansion) Exfoliation
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Unformatted text preview: : fracturing into thin slabs of rock parallel to its exposed surface Erosion by wind or water Abrasion by glaciers Abrasion by glaciers Biological activities actions of plants, animals actions of plants, animals 4.1 Weathering of materials 4 Weathering and erosion The progressive disintegration of a granite block of granite which “rots” gives a “ball“ and sand Physical disintegration of granite Physical weathering Physical disintegration of granite Physical weathering Heat causes Expansion; cooling causes contraction. Different minerals expand and contract at different rates, causing stresses along mineral boundaries. Repeated daily heating and cooling of rock causes the rock to break down....
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