When rock buried deep in the earth is gradually exposed, the reduction in pressure typically causes cracks and fissures to form in the rock. This increases the surface area of the rock, allowing air and water to better react with various minerals in the rock, and the physical effect of thermal expansion and contraction also causes the rock to loosen and disintegrate. As a result, rock is eventually transformed into sand, mud, and soil. This effect is termed “weathering”.

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