The Aorounga structure is situated within the Sahara Desert of Northern Chad, about 110 kilometers southeast of the Emi Koussi volcano in the Tibesti Massif. This structure is poorly explored and its exact size and formation age are still disputed. French researchers have collected samples from the structure, which show evidence of shock metamorphism. This shuttle image clearly shows the two broad concentric rings that delineate the Aorounga structure. Each ring rises approximately 100 meters above the surrounding plains, and the two are separated by a depression of uniform width. A central uplift would be located within the central depression. The sandstones forming the outer ring dip steeply toward the depression. The streaks mark the prevailing wind direction and represent sand deposits that occupy shallow, linear, wind-cut valleys.
Space shuttle image STS38-77-005.