Regolith may also be eroded and transported by other geomorphic agents, if it is exposed to them. B. Physical weathering - fragmentation of rock by mechanical action. Freeze-thaw action . Especially in places where freeze and thaw is frequent, this physical weathering process can be severe. Plant root growth .
Roots can penetrate cracks and physically pry rocks apart as the root grows in size.
Pressure-release action . Intrusive igneous rocks form at depth by gradual cooling in a magma chamber. As the crustal overburden is eroded away, the release in confining weight allows rocks to expand and fracture in concentric layers, like the skin on an onion. C. Chemical weathering - weakening of rock by slow chemical reactions that change minerals from more to less resistant forms. Hydrolysis - chemical reaction of water with minerals.