It covers an area of approximately 78,000 square kilometres (30,000 sq mi).

[1] The sand dunes in the erg are formed by the wind, and can be up to 120 metres (390 ft) high.

[1] It is a desert natural region that receives less than 50 mm (1,96 in) of rainfall per year.

[2] The mean elevation of the Grand Erg Occidental is about 500 m, on average higher than the elevation of the Grand Erg Oriental, but not as high as the neighboring Tademaït to the southwest.

This desolate region is a practically uninhabited area; there are no permanent villages.