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 Qinā on the Nile. Near Qinā, 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 Qinā 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 Shāʿib al-Banāt, 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 Aswān, 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-Kabīr 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-Khārijah and Al-Dākhilah. Farther north are the oases of Al-Farāfirah and Al-Baḥriyyah. Northwestward from the latter the plateau continues to fall toward the Qattara Depression (Munkhafaḍ al-Qaṭṭārah), 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.

Sinai Peninsula

The Sinai Peninsula comprises a wedge-shaped block of territory with its base along the Mediterranean Sea coast and its apex bounded by the Gulfs of Suez and Aqaba; it covers an area of approximately 23,000 square miles (59,600 square km). Its southern portion consists of rugged, sharply serrated mountains. These reach elevations of more than 8,000 feet (2,400 metres); among them is Mount Catherine (Jabal Kātrīnā), Egypt’s highest mountain, which has an elevation of 8,668 feet (2,642 metres). The central area of Sinai consists of two plateaus, Al-Tīh and Al-ʿAjmah, both deeply indented and dipping northward toward Wadi al-ʿArīsh. Toward the Mediterranean Sea, the northward plateau slope is broken by dome-shaped hills; between them and the coast are long, parallel lines of dunes, some of which are more than 300 feet (100 metres) high. The most striking feature of the coast itself is a salt lagoon, Lake Bardawīl, which stretches for some 60 miles (95 km).