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.
Stone pavements are important for a number of reasons:
Pavements are best developed where vegetation is absent. While not yet fully understood, it is believed that paved areas adversely affect plant growth; they tend to be locales where the soil is relatively saline or alkaline, and where the soil has a relatively low infiltration capacity. Pavements, then, arenatural water-harvesting systems: they shed water readily, and thereby promote growth in adjacent non-paved areas and geomorphological features such as washes.
The coarse (stony) surface of pavements consists of either primary or secondary fragments. Primary fragments are similar to the coarse material located within the matrix; conversely, secondary fragments derive from primary fragments (such as boulders) through disintegration processes. The stony surfaces can be hypothesized to arise from one or more fragment-concentrating sequences.
Deserts of the World
This site last updated October 5, 1998