rocks (granite) formed as igneous intrusions under pressure // weathering + erosion remove overlying rock // pressure released // underlying rock expands // fracture + vulnerable
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Exfoliation / insolation weathering
large temp change // heating + cooling // (expansion + contraction) // stresses in rock layers // outer layers quicker than inner // outer layers peel off
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oxidation
oxygen (aq) react with rock minerals (especially iron) // form oxides + hydroxides // weakens // disintegrates // discolours
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hydrolysis
water + rock minerals = insoluble precipitate // achilles heel of granite (feldspar --> kaolinite (china clay)
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carbonation
rain + CO2 --> weak carbonic acid // converts to soluble CaCO + H2O + CO2 // then insoluble calcium bicarbonate
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soil creep (solifluction)
turf binds to top layer of soil // underneath layers are able to move freely // water inc. weight + dec. gravity // particles move past each other (soil creep plus - permafrost regions - wetter)
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slump
increased weight + decreased friction in permeable top layer rock
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meanders
sinuosity ratio 1.5 or more // water flow deflected (upper course interlocking spurs) // lower down more pronounced bends (lateral erosion)
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levees
water floods // loses competence // deposits material
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