Grand Erg Occidental Grand Erg Occidental The Grand Erg Occidental (, al-ʿIrq al-Gharbī al-Kabīr), (also known as the Western Sand Sea) is the second largest erg in northern Algeria after the Grand Erg Oriental. It covers an area of approximately . The sand dunes in the erg are formed by the wind, and can be up to high. Certain crescent-shaped dunes, known as barchans, are actually mobile; the wind can push these dunes as much as 20 to 30 m (65-100 ft) in one year. It is a desert natural region that receives less than 50 mm (1,96 in) of rainfall per year.
Issaouane Erg which can take hundreds of thousands of years to form; mesoscale dunes (including the stardunes), which form on the mega dunes; and yet smaller ones which migrate over the bigger ones. In the NASA images, the light-blue spots in the valleys between the dunes (which are red from iron oxide) are "sabkhah", or salt flats, left after the evaporation of accumulated water. Neolithic artifacts, sculptures and paintings have been found in the Issouane Erg. from the Kiffian culture. The Issaouane Erg contains oil; the Tifernine oilfield is explored by the Algerian state oil company Sonatrach, which began developing the oilfield