The disintegration of rocks without any change in their chemical composition is called mechanical weathering.
The minerals in the rocks expand because of heat and contract when the temperature decreases. Due to such continuous contracting and expansion, tension develops in the rock particles.
Each mineral reacts differently to the temperature; some minerals expand more, while others do not expand as much. Consequently, the tension formed in the rocks also increases and decreases. As a result, cracks develop in the rocks and they break.
In areas where the temperatures drop below 0°C for quite some time, the water accumulated in the cracks and crevices in the rocks freezes. Its volume increases which leads to tension in the rocks and they shatter.
When the alkaline water of the sea fills in the cracks of the rocks, the soluble minerals in the rock get dissolved leading to the formation of small holes in the rocks.
Because of the heat, this water turns into water vapour and only crystals of alkaline materials remain in the rocks. Crystals occupy more space which causes tension in the rock.
Sometimes the outer layers of the rocks exert pressure on the inner or lower layers. When this pressure ceases to exist, the lower or inner layers get freed from the pressure. This also leads to weathering.
In areas of heavy rainfall soaking of rock water also causes weathering of some rocks like sandstone and conglomerate. When water penetrates such rocks, the particles get loose and separate from the main rock.
