Shuttle images reveal Egypt's lost great lake

Alexandra Witze -

Desert drainage patterns point to ancient oases in Sahara.

A huge lake once waxed and waned deep in the sandy heart of the Egyptian Sahara, geologists have found.

Radar images taken from the space shuttle confirm that a lake broader than Lake Erie once sprawled a few hundred kilometers west of the Nile, researchers report in the December issue of Geology. Since the lake first appeared around 250,000 years ago, it would have ballooned and shrunk until finally petering out around 80,000 years ago.

Knowing where and when such oases existed could help archaeologists understand the environment Homo sapiens traveled while migrating out of Africa for the first time, says team leader Ted Maxwell, a geologist at the Smithsonian National Air and Space Museum in Washington, D.C. Modern humans arose in Africa about 200,000 years ago.

“You realize that hey, this place was full of really large lakes when people were wandering into the rest of the world,” he says.

Since then, desert winds have eroded and sands have buried much of the region’s landscape, says Maxine Kleindienst, an anthropologist at the University of Toronto. But during next summer’s field season, she and her colleagues will be checking for ancient shorelines at the elevations suggested in the new paper.

Other studies have found evidence of mega-lakes in Chad, Libya and Sudan at various points over the past 250,000 years. The new study targeted Egypt, some 400 kilometers west of the Nile, where in the 1980s researchers reporting finding fish fossils in the desert.

That discovery, says Maxwell, triggered scientists to think about how those fish could have gotten there. In 2000, astronauts on the space shuttle Endeavour used a radar instrument to take high-resolution pictures of the area’s topography. Maxwell and his colleagues recently analyzed those pictures to deduce how water would have drained across northeastern Africa over the past few hundred thousand years, ever since the Nile was born.

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T. Maxwell

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