Long Durational Natural Phenomenon

Existence of Eye of the Sahara (Richat Structure)

Duration: 100 Million years

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Cover photograph CC BY-SA 3.0 Atamari

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. The structure is 40 kilometers in diameter. The exposed sedimentary rock ranges in age from Late Proterozoic within the center of the structure to Ordovician sandstone around its edges. Differential erosion of resistant layers of quartzite has created high-relief circular cuestas. Exposed within the interior of the Richat Structure are a variety of intrusive and extrusive igneous rocks. They include rhyolitic volcanic rocks, gabbros, carbonatites, and kimberlites.

Photograph Public Domain NASA

According to field mapping and aeromagnetic data, gabbroic rocks form two concentric ring dikes. Initially interpreted as an asteroid impact structure because of its nearly perfect circular structure, it is now argued to be a highly symmetrical and deeply eroded geologic dome. 

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