Weatherin1 - Weathering Physical weathering physical...

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Weathering Physical weathering physical weathering is the disintegration of rock and soil aggregates, by physical (mechanical) processes acting primarily on pre-existing fractures (e.g. joints, cracks between mineral grains); reduces size of fragments according to rock and soil structure (producing grains, crystals, blocks, slabs, etc.), with no change in composition and Processes 1. stress (pressure) release: disintegration of rock in parallel sheets as it expands in response to the removal of confining stress o most common mechanism of stress release is removal of overlying rock by erosion; thus this process is controlled by erosion but subsequently controls erosion o the dilation fractures conform to the surface topography and increase in spacing with depth (e.g. from a few cm at the surface to a few metres at 30 m in the Sierra Nevada Mountains of Yosemite National Park) o thermal contraction due to cooling counteracts expansion; therefore stress release is most pronounced near the surface where the rocks have already cooled and contracted o also most common in massive rocks: higher thermal conductivity causes heat loss and thus reduces counter influence of cooling and contraction, fractured or thinly bedded rock will expand with out sheeting, massive rocks store stress until overburden pressure is very low (i.e. about 100 m of overburden) o stress release causes exfoliation: the separation of concentric layers of rock
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Weatherin1 - Weathering Physical weathering physical...

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