These microorganisms assist in the breakdown and weathering of rocks. As water evaporates moisture from rocks located in arid climates mineral salts develop from mineral crystals. The crystals grow, spreading apart mineral grains in the process, and eventually break apart rocks. Crystal structures of minerals become stressed during contraction and expansion and the mineral crystals separate. Frost-wedging forces portions of rock to split apart.
Exfoliation occurs as sheets or slabs of the cracked rock slip off and become further eroded.
Domes form as the unloading and exfoliation weathering processes continue. Although one weathering process can dominate in a given area, physical and chemical weathering processes occur simultaneously to break down rock parent material. Rocks that are formed under intense temperature and pressure and cool rapidly forms crystalline structures in minerals that are less stable when exposed to low temperatures and pressures at Earth's surface , so they will weather more rapidly. Rocks that are formed under intense temperature and pressure, but cool more slowly and later in the volcanic magma cooling process, are more stable when exposed to the low temperatures and pressures at Earth's surface. Bonds holding atoms together determine mineral hardness.