The desert containing Mauritania’s circular Richat Structure, or “Eye of Africa,” is the Sahara.
The Richat Structure lies near Ouadane on the Adrar Plateau in northwestern Mauritania. From space it appears as a huge bull’s-eye, with alternating concentric rings spanning about 40 kilometres. Its striking shape once encouraged speculation that it was an ancient meteorite impact crater.
Geologists now interpret it as a deeply eroded geological dome associated with an alkaline igneous complex. Subsurface molten rock pushed the overlying layers upward, and later erosion removed softer materials more quickly than resistant rocks, exposing the ringed structure. Its central rocks include rhyolites, gabbros and hydrothermally altered formations.
The feature is scientifically and archaeologically important. Acheulean stone tools have been found around its outer depressions, where ancient people could access workable quartzite. The biggest mix-up is calling it a crater: despite its circular appearance, researchers found no convincing evidence of a hypervelocity impact. Its “Eye of Africa” nickname comes from satellite imagery, not from its geological origin.