Richat Structure

The Richat Structure, or Guelb er Richât (Arabic: قلب الريشات, romanized: Qalb ar-Rīšāt, Hassaniyya: [galb er.riːʃaːt] ), often called the Eye of Africa is a prominent circular geological feature at the northwestern edge of the Taoudeni Basin, on the Adrar Plateau of the Sahara. It is located near Ouadane in the Adrar Region of Mauritania. In Hassaniya Arabic, rīšāt means feathers and it is also known locally in Arabic as tagense, referring to the circular opening of the leather pouch that is used to draw water from local wells. It is an eroded geological dome, 40 kilometres (25 mi) in diameter, caused by a subsurface igneous intrusion deforming the overlying sedimentary rock layers, causing the rock to be exposed as concentric rings with the oldest layers exposed at the centre of the structure. Igneous rock is exposed inside and there are rhyolites and gabbros that have undergone hydrothermal alteration, and a central megabreccia. The structure is also the location of exceptional accumulations of Acheulean Paleolithic stone tools. It was selected as one of the 100 geological heritage sites identified by the International Union of Geological Sciences (IUGS) to be of the highest scientific value.