Extremely common in hot deserts, stone pavements are hard surfaces consisting of a angular or rounded rock fragments, usually one or two stones thick, set in or on a matrix of finer material. Hammada is a term associated with boulder-strewn surfaces or rock surfaces with a scatter of stones, while reg is generally applied to pavements covered by smaller stones.
Pavements can occur on spatial scales ranging from a few square meters to many square kilometers.
Pavements are best developed where vegetation is absent. The stony surfaces can be hypothesized to arise from one or more fragment-concentrating sequences. Aeolian deflation of fine materials. Stone pavements are easy to explain using the deflation hypothesis, and while it is clear that wind can and does remove loose, fine particles, arguments exist that persuade against deflation being the sole causative agent. The fine material at desert surfaces often aggregates into a thin crust, which is strong, dense, relatively impermeable, and protective of the underlying particles.