. Physical or mechanical weathering processes depend on some applied forces.
Unloading and Expansion
Removal of overlying rock load because of continued erosion causes vertical pressure release. Thus, the upper layers of the remaining rock expand to produce disintegration of rock masses. Fractures will develop roughly parallel to the ground surface. In areas of curved ground surfaces, arched fractures tend to produce massive sheets or exfoliated slabs.
Temperature and Expansion
With rising in temperature, every mineral expands and pushes against its neighbour and as the temperature falls, a corresponding contraction takes place. Due to differential heating and the resulting expansion and contraction of surface layers and their subsequent exfoliation from the surface results in smooth rounded surfaces in rocks. In rock like granites, smooth-surfaced and rounded small to big boulders called tors form due to such exfoliation.
Freezing, Thawing and Frost Wedging
Cycles of freezing and thawing (the weather becomes warmer and causes snow and ice to melt) cause frost weathering. It is most effective at high elevations in mid-latitude where freezing and melting is often repeated. Rapid freezing of water causes its sudden expansion and high pressure. The resulting expansion affects joints, cracks, and small intergranular fractures to become wider and wider till the rock breaks apart.
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