Richat Structure
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The Richat Structure, a prominent circular feature in the Sahara desert of Mauritania, 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.
Original entry was from the NASA Earth Observatory; [1] (http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=9319)
External links
- NASA Earth Observatory page (http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=9319)
- Astronomy Picture of the Day (http://antwrp.gsfc.nasa.gov/apod/ap021028.html)it:Struttura di Richat