Mechanical weathering breaks large rocks into smaller
ones but does not alter the rock’s chemical nature or its
minerals. Think of grinding a rock in a crusher; the fragments
are no different from the parent rock, except that
they are smaller.
Five major processes cause mechanical weathering:
pressure-release fracturing, frost wedging, abrasion, organic
activity, and thermal expansion and contraction.
Two additional processes—salt cracking and hydrolysis
expansion—result from combinations of mechanical and
chemical processes.