Photo: Once Lush Sahara Dried Up Over Millennia, Study Says



Fed by prehistoric groundwater, Lake Yoa (above) in remote northern Chad, has persisted despite thousands of years of constant drought and searing heat.

A new analysis of the lake's bottom deposits suggests that the Sahara turned from green savanna to arid desert more slowly than previously thought.

Photograph courtesy S. Kröpelin/University of Cologne


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