ABSTRACT
Climate, geology, and the age of the ground surface define the features of an arid environment. In general, arid regions are characterized by two kinds of morphology, namely, shields (platforms) and shelves (basins) (see Figure 1.3). The former is located in extremely stable seismic zones of tectonic origin such as the western Arabian Peninsula, the Sahara in Africa and southern Africa, parts of Asia, India, and Australia. Arid region shields are often dominated by eroded surfaces on volcanic rocks, which constitute the base of stratigraphic sequences. There are also platforms developed on horizontally layered sedimentary rocks like the Nubian sandstone in North Africa. The origin of these plains is not connected to their current aridity. Intermountain basin deserts are dominated by a succession of mountains and troughs often characterized by closed drainage basins.
