Above in false colors: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 bullÂ’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.
Note: Not a meteor impact site, not a hurricane, not a volcano.