Pressure Release: When rocks are formed deep in the earth's crust, the pressure is high. As this pressure is released when they are at or near the surface, the rocks begin to expand. Cracks and fractures occur as "pressure is released". If a rock has no natural joints or bedding planes, these cracks and fracture may be more obvious.
Exfoliation: Different minerals in rocks will have varying rates of expansion and contraction so when temps have a great range the expansion/contraction will produce stresses. It creates "oinion skin" weathering or exfoliation.
Frost Shattering: Water expands by 9% when it freezes so pressure is exerted on rocks when temperatures fall and water is in the crevices/joints. Angular fragments of rocks are produced as the rock is "shattered" during this process.
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