Issaouane Erg confined to basins. Sand in the Issaouane Erg, below the level of the sand dunes, has accumulated to a depth of 20 to 30 meters. It has barchan dunes as well as star dunes of 300 to 430 meters high. The presence of both barchan dunes (which form due to unidirectional winds) and star dunes (which form when winds from various directions deposit sand) "suggests that wind regimes have changed over time". NASA's "Earth Observatory" notes all three types of erg dunes are present in the photos of the Issaouane Erg taken from the International Space Station: stationary mega dunes,
Erg Iguidi Erg Iguidi The Erg Iguidi (), is a large erg in the area of Tindouf in southwestern Algeria extending into northern Mali and Mauritania. The Erg Iguidi is a sandy desert with a clear pattern of narrow linear dunes stretching for a length of 400 km. Part of the greater Sahara, it is located in its northwestern region and is characterized by Harmattan withering winds. The highest point is 540 m. Compared to the neighboring Erg Chech to the south, this erg is relatively humid. Groundwater is especially abundant towards the north-eastern edge of the Erg Iguidi. There are patches