ouadane

The Eye of the Sahara, seen here in an aerial image provided by the ISS, is is a prominent circular feature in the Sahara desert near Ouadane, west–central Mauritania. It was initially thought to have been caused by a meteor impact, but lack of strong evidence has turned many off to this hypothesis. At 30 miles wide (50 km) it is easily visible from space.

The above image of Mauritania, the Eye of the Sahara, is one of the photographs included in the latest book from retired astronaut Chris Hadfield. 

The Richat Structure, aka the Eye of the Sahara and Guelb er Richat, is a prominent circular feature near Ouadane, Mauritania. This structure is a deeply eroded, slightly elliptical, 40 km in diameter dome. The sedimentary rock exposed in this dome ranges in age from Late Proterozoic within the center of the dome to Ordovician sandstone around its edges. 

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The Eye of the Sahara

Richat Structure

The Richat Structure, also known as the Eye of the Sahara and Guelb er Richat, is a prominent circular feature in the Sahara desert near Ouadane, west–central Mauritania. This structure is a deeply eroded, slightly elliptical, 40 km in diameter dome. The sedimentary rock exposed in this dome ranges in age from Late Proterozoic within the center of the dome to Ordovician sandstone around its edges. The sedimentary rocks comprising this structure dip outward at 10°–20°. Differential erosion of resistant layers of quartzite has created high-relief circular cuestas. Its center consists of a siliceous breccia covering an area that is at least 30 km in diameter

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(sunday off-topic-ness:))