Richat Structure

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Satellite picture of the Richat Structure

The Richat Structure, a prominent circular feature in the Sahara desert of Mauritania near Ouadane, has attracted attention since the earliest space missions because it forms a conspicuous bull’s-eye in the otherwise rather featureless expanse of the desert. Described by some as looking like an outsized ammonite in the desert, the structure, which has a diameter of almost 50 kilometers (30 miles), has become a landmark for shuttle crews. Initially interpreted as a meteorite impact structure because of its high degree of circularity, it is now thought to be merely a symmetrical uplift (circular anticline) that has been laid bare by erosion. Paleozoic quartzites form the resistant beds outlining the structure.

A topographic reconstruction (scaled 6:1 on the vertical axis) from satellite photos. False coloring as follows: bedrock=brown, sand=yellow/white, vegetation=green, salty sediments=blue

Original entry was from the NASA Earth Observatory; [1]

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Guillaume Matton, Michel Jébrak and James K.W. Lee (August 2005). "Resolving the Richat enigma: Doming and hydrothermal karstification above an alkaline complex". Geology 33 (8): 665-668. DOI:10.1130/G21542.1.