Sahara Desert, forms an integral part of the section of North Africa known as the Maghreb. This area includes Morocco, Tunisia, and the northwestern portion of Libya known historically as Tripolitania.
Tell Atlas, High Plateaus and the Saharan AtlasStretching from the Moroccan border the Tell Atlas, including the Djebel Babor formation, is the dominant northwestern mountain range. Stretching more than 600 kilometers eastward from the Moroccan border, the High Plateaus (often referred to by their French name Hauts Plateaux) consist of undulating, steppe-like plains lying between the Tell and Saharan Atlas ranges. The plateaus average between 1,100 and 1,300 meters in elevation in the west, dropping to 400 meters in the east. So dry that they are sometimes thought of as part of the Sahara, the plateaus are covered by alluvial debris formed when the mountains eroded. An occasional ridge projects through the alluvial cover to interrupt the monotony of the landscape.
Higher and more continuous than the Tell Atlas, the Sahara Atlas range is formed of three massifs: the Ksour Range near the Moroccan border, the Amour Range, and the Ouled-Naïl Range south of Algiers. The mountains, which receive more rainfall than those of the High Plateaus, include some good grazing land. Watercourses on the southern slopes of these massifs disappear into the desert but supply the wells of numerous oases along the northern edge of the desert, of which Biskra, Laghouat, and Béchar are the most prominent.
Northeastern AlgeriaEastern Algeria consists of a massive area extensively dissected into mountains, plains, and basins. It differs from the western portion of the country in that its prominent topographic features do not parallel the coast. In its southern sector, the steep cliffs and long ridges of the Aurès Mountains create an almost impenetrable refuge that has played an important part in the history of the Maghrib since Roman times. Near the northern coast, the Petite Kabylie Mountains are separated from the Grande Kabylie range at the eastward limits of the Tell by the Soummam River. The coast is predominantly mountainous in the far eastern part of the country, but limited plains provide hinterlands for the port cities of Bejaïa, Skikda, and Annaba. In the interior of the region, extensive high plains mark the region around Sétif and Constantine; these plains were developed during the French colonial period as the principal centers of grain cultivation. Near Constantine, salt marshes offer seasonal grazing grounds to seminomadic sheep herders.
The Algerian portion of the Sahara extends south of the Saharan Atlas for 1,500 kilometers to the Niger and Mali frontiers. The desert is an otherworldly place, scarcely considered an integral part of the country. Far from being covered wholly by sweeps of sand, however, it is a region of great diversity. Immense areas of sand dunes called areg (sing., erg) occupy about one-quarter of the territory. The largest such region is the Grand Erg Oriental (Great Eastern Erg), where enormous dunes two to five meters high are spaced about 40 meters apart. Much of the remainder of the desert is covered by rocky platforms called humud (sing., hamada), and almost the entire southeastern quarter is taken up by the high, complex mass of the Ahaggar and Tassili n'Ajjer highlands, some parts of which reach more than 2,000 meters. Surrounding the Ahaggar are sandstone plateaus, cut into deep gorges by ancient rivers, and to the west a desert of pebbles stretches to the Mali frontier.
The desert consists of readily distinguishable northern and southern sectors, the northern sector extending southward a little less than half the distance to the Niger and Mali frontiers. The north, less arid than the south, supports most of the few persons who live in the region and contains most of the desert's oases. Sand dunes are the most prominent features of this area's topography, but between the desert areas of the Grand Erg Oriental and the Grand Erg Occidental (Great Western Erg) and extending north to the Atlas Saharien are plateaus, including a complex limestone structure called the M'zab where the M'zabite Berbers have settled. The southern zone of the Sahara is almost totally arid and is inhabited only by the Tuareg nomads and, recently, by oil camp workers. Barren rock predominates, but in some parts of Ahaggar and Tassili n'Ajjer alluvial deposits permit garden farming.