The Atlas system takes the shape of an extended oblong, enclosing a complex of plains and plateaus, and it contains distinct northern and southern ranges named the Tell Atlas and Saharan Atlas, respectively. The ranges rim the extensive High Plateaus of eastern Morocco and northern Algeria. To the east in Tunisia they join together in the Tébessa and Medjerda mountains, while to the west in Morocco they merge into the Middle Atlas and the high, rugged peaks of the High Atlas. The Anti-Atlas extends southwestward from the High Atlas to the Atlantic Ocean. Geologically, the Tell Atlas is a young, folded mountain range related to the Alpine system of Europe. The southern Saharan Atlas, however, belongs to a distinct structural grouping, that of the vast, ancient plateaus of the African continent. The Atlas Mountains have a total length of about 1,200 miles (2,000 km) and reach their maximum elevation at Mount Toubkal, which rises to 13,665 feet (4,165 m).

The Atlas Mountains are a meeting place of two different kinds of air masses—humid and cold polar air masses that come from the north and the hot and dry tropical air masses that move up from the south. Winter in the Atlas is hard, imposing severe living conditions upon the inhabitants. These include principally the Berbers, who have survived there, preserving their own language, traditions, and beliefs. The great Maghribian wadis, the Moulouya and the Chelif, issue from the Atlas Mountain ranges. There is considerable erosion aggravated by the sparseness of vegetation. The clearance of land for agriculture has long contributed to the reduction of oak, pine, and cedar forests in the Atlas ranges, but afforestation programs in Algeria and Morocco have helped to reverse this deforestation. The geologic formations are rich in minerals, the most important of these being lead, zinc, copper, iron, manganese, and phosphate.