Atlas Mountains, system of ranges and plateaus in NW Africa, extending c.1,500 mi (2,410 km) from SW Morocco, through N Algeria, to N Tunisia; Jebel Toubkal (13,671 ft/4,167 m), in SW Morocco, is the highest peak. The Atlas Mts., predominantly folded mountains of sedimentary rock, were uplifted during the late Jurassic period. Geologically related to the Alpine system of Europe, they are separated from the Sierra Nevada of Spain by the Strait of Gibraltar and from Sicily and the Apennines of Italy by the Mediterranean Sea; the Canary Islands are a westward extension. The Atlas system is most rugged in Morocco, where, from north to south, the Rif (or Rif Atlas), Middle Atlas, High or Grand Atlas (the highest part of the system), and Anti-Atlas are found; fertile lowlands separate the ranges. In Algeria the system becomes a series of plateaus, with the Tell Atlas and the Saharan Atlas rimming the extensive Plateau of the Chotts before converging in Tunisia.
The Atlas Mts. are a climatic barrier between the Mediterranean basin and the Sahara Desert. The slopes facing north are generally well watered and have important farmland and forests; on these slopes are the headwaters of many streams used for irrigation. The slopes facing south and the drier areas of the system are generally covered with shrub and grasses and have salt lakes and salt flats; sheep grazing is important there. The Atlas Mts. are rich in minerals, especially phosphates, coal, iron, and oil.