Egypt's Western Desert covers about 700,000 square kilometers and accounts for about two-thirds of Egypt's total land mass. It stretches west from the Nile river onto the Libyan border and southwards from the Mediterranean coast onto the Sudanese border. In the past, it has been known by different names but as it constitutes the entire western portion of Egypt, it is locally known as the Western Desert. It is also known as the Eastern or Egyptian Sahara.
In sharp contrast to Egypt's other two dserts (Sinai and the Eastern Desert), the Western Desert is a boundless plain of barren plateaus and sand dunes. The desert's Gilf el Kebir plateau has an altitude of about one thousand meters, an exception to the uninterrupted territory of basement rocks covered by layers of horizontally bedded sediments forming a massive plain or low plateau. The whole area is composed of a flat plain gently sloping towards the Mediterranean Sea. The tilted rock strata are eroded as the land rises southwards, resulting in a series of scarps that run parallel to the sea, and form cliffs sometimes several hundred metres high. At some points at the base of the scarps the wind has excavated, depressions which reach into an aquifyer layers lying under the whole of the Sahara, form oases
Scarps and deep depressions are scattered in different parts of this desert, but no rivers or streams drain into or out of the area. The seven main depressions of the Egyptian Sahara are Siwa and Qattara in the north, Fayoum, further south not very far from Cairo, Bahareya, Farafra, Dakhla and Kharga respectively form a sort of crescent opening towerds the east further south.
This crescant or bow was the way the Nile ran its course several thousand years ago, long before the eve of the first Nile civilizations. The waters popping up now from deep underground are leftovers from those days. These reservoirs were long considered a long time resource, and large funds were pumped into the region. When newer research proved the reserves more limited, and sufficient for only 100 years of today's exploitation, the large schemes for development were left dead.
All but one of these depressions are considered oases as the Qattara depression is mostly below sea level (its lowest point being 133 m. below sea level) and is sparsely inhabited. Badlands, salt marshes and salt lakes constitute most of this approximately 15,000 square kilometer depression.
Limited agricultural production, the presence of some natural resources and permanent settlements are found in the other six depressions. All of them have fresh water provided by the Nile or by local groundwater (artesian wells). There are a few scattered uninhabited small oases, usually linked to the major depressions, where water can be found by digging to a few feet in depth.
Aside the scarps, the general flatness is only interrupted by a series of plateaus and massifs, around the convergence of the Egyptian-Sudanese-Libyan Borders. The Gilf el Kebir plateau rises about 300 metres above the general plain, and lies entirely in Egypt. It roughly equals Switzerland in size, and is similar in structure to the other sandstone plateaus of the central Sahara. It's South-eastern part is well defined on all sides, with sheer cliffs and deep, narrow wadis. The North-east part, separated from the other half by a broad valley called the "Gap" is more broken, and supports three large wadis with live vegetation.
The huge volume of sand excavated by the wind from the Quattara and other lesser depressions have been organised into a huge area of parallel sand dunes, hundreds of kilometres in length, and occasionally reaching heights of a hundred metres. This Great Sand Sea occupies most of the north-eastern part of the Libyan Desert south of Siwa and to the west of Baharya and Farafra, giving way to gravel plains, mudpans and the perfectly flat and featureless Selima Sand Sheet plains further south roughly along latitude 23 North. A tongue of the Great Sand Sea turns west, and continues accross the flat plains in Libya, where it is called the Calanascio Sand Sea. After losing height and tapering off, the dunes gain strength once more, and form the Rebiana Sand Sea that occupies the western edge of the Libyan Desert.
The Egyptian government has considered the Western Desert a frontier region and has divided it into two governorates at about the 28th parallel: Matruh to the north and the New Valley (Al Wadi Al Gedid) to the south.