The Eastern Desert
The Eastern Desert comprises almost one-fourth of the land surface of Egypt and covers an area of about 85,690 square miles (221,900 square km). The northern tier is a limestone plateau consisting of rolling hills, stretching from the Mediterranean coastal plain to a point roughly opposite Qin? on the Nile. Near Qin?, the plateau breaks up into cliffs about 1,600 feet (500 metres) high and is deeply scored by wadis, which make the terrain very difficult to traverse. The outlets of some of the main wadis form deep bays, which contain small settlements of seminomads. The second tier includes the sandstone plateau from Qin? southward. The plateau is also deeply indented by ravines, but they are relatively free from obstacles, and some are usable as routes. The third tier consists of the Red Sea Hills and the Red Sea coastal plain. The hills run from near Suez to the Sudanese border; they are not a continuous range but consist of a series of interlocking systems more or less in alignment. A number of peaks in the Red Sea Hills rise to more than 6,000 feet (1,800 metres), and the highest, Mount Sh??ib al-Ban?t, reaches 7,175 feet (2,187 metres). They are geologically complex, with ancient igneous and metamorphic rocks. These include granite that, in the neighbourhood of Asw?n, extends across the Nile valley to form the First Cataract—that is, the first set of rapids on the river. At the foot of the Red Sea Hills the narrow coastal plain widens southward, and parallel to the shore there are almost continuous coral reefs. In popular conception and usage, the Red Sea littoral can be regarded as a subregion in itself.
The Western Desert
The Western Desert comprises two-thirds of the land surface of Egypt and covers an area of about 262,800 square miles (680,650 square km). From its highest elevation—more than 3,300 feet (1,000 metres)—on the plateau of Al-Jilf al-Kab?r in the southeast, the rocky plateau slopes gradually northeastward to the first of the depressions that are a characteristic feature of the Western Desert—that containing the oases of Al-Kh?rijah and Al-D?khilah. Farther north are the oases of Al-Far?firah and Al-Ba?riyyah. Northwestward from the latter the plateau continues to fall toward the Qattara Depression (Munkhafa? al-Qa???rah), which is uninhabited and virtually impassable by modern vehicles. West of the Qattara Depression and near the Libyan border is the largest and most populous oasis, that of Siwa. It has been inhabited for thousands of years and is less influenced by modern development. South of the Qattara Depression, and extending west to the Libyan border, the Western Desert is composed of great ridges of blown sand interspersed with stony tracts. Beyond the Qattara Depression northward, the edge of the plateau follows the Mediterranean Sea, leaving a narrow coastal plain.