Dune Morphology and Dynamics

Quartz sand dominates aeolian deposits in arid regions, as dust-sized particles are carried out of the desert entirely or are trapped by vegetation or rough surfaces on desert margins (Tsoar and Pye 1987). Most (>95%) sand occurs in accumulations known as sand seas or ergs (Wilson 1973) that comprise areas of dunes of varying morphological types and sizes as well as areas of sand sheets. Smaller dune areas are known informally as dunefields. Major sand seas occur in the old world deserts of the Sahara, Arabia, central Asia, Australia, and southern Africa, where sand seas cover between 20 and 45% of the area classified as arid (Fig. 18.1). In North and South America there are no large sand seas, and dunes cover less than 1% of the arid zone. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.