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 Chigaga Erg Chigaga Erg Chegaga (or Chigaga) is one of two major Saharan ergs of the Sahara in Morocco, the other being the Erg Chebbi near Merzouga. This dunes are located in the Drâa-Tafilalet area about 50 km west of the rural town of M'Hamid El Ghizlane, itself located about 98 km south of the town of Zagora. With a length of approximately 40 km to 15 km width, some dunes are around 60m high (significantly less than the dunes at Erg Chebbi with up to 150m), it is the largest and wildest of Morocco. Because it is relatively difficult to