Pressure release (also known as dilation and unloading) refers to the removal of overlying materials due to processes such as erosion. The removal of weight hence pressure causes rocks beneath to expand and fracture overtime creating sheet joints of pseudo-bedding planes parallel to the surface. These fractures (cracks) formed will consequently be affected by weathering. As a result large rock sheets may break off (slabs of rocks called exfoliation sheets) creating a rounded appearance (exfoliation domes) to the landscape.


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Geological exfoliation of granite dome rock caused by pressure release

Pressure release is unlike other types of physical weathering as although it does involve rocks decomposing in situ, this type of weathering is not caused by elements of the weather.