Iguidi

a sandy desert (erg) in the Western Sahara of Algeria and Mauritania, between the Dra Plateau in the northwest and the El Eglab Plateau in the southeast. The dunes lie on a crystalline foundation and stretch 400 km from east-northeast to west-southwest in a strip 50–100 km wide. They form narrow ridges held in place by vegetation. Groundwater is especially abundant along the northeastern margin of the Iguidi. The region is used for pasture in the summer.