Largest desert in the world, encompassing almost all of northern Africa.
Covering an area of about 3,500,000 sq mi (9,065,000 sq km), it is bounded by the Atlantic Ocean , the Atlas Mountains , the Mediterranean Sea , the Red Sea , and the Sahel region. It includes portions of several countries, including Morocco, Algeria, Tunisia, Libya, Egypt, Mauritania, Mali, Niger, Chad, and The Sudan. Principal topographic features include large oasis depressions, extensive stony plains, rock-strewn plateaus, abrupt mountains, sand sheets and dunes, and sand seas. Huge areas of it are empty, but scattered clusters of inhabitants survive in fragile ecological balance wherever water sources occur. Sedentary living is restricted to oasis areas. See also Libyan Desert .