the sands of Egypt's vast Sahara desert and lake

An ancient lake bed 350 kilometers long has been discovered beneath the sands of Egypt's vast Sahara desert. Geologist Ted Maxwell at the Smithsonian National Air and Space Museum in Washington DC, and colleagues examined high resolution pictures (shown below) of south western Egypt taken by NASA's Shuttle Radar Topography Mission (SRTM), a modified radar system used onboard Space Shuttle Endeavour in February 2000 and identified a region in an area called Tushka where water formed a lake after overflowing from the Nile. The lake appeared around 250,000 years ago - during a period of wet climate when the region would have been covered in grasslands - and dried up 80,000 years ago, covering an area of 68,200 square kilometers at its peak.

The extent of the lake explains how fossilized fish from the last interglacial period ended up at Bir Tarfawi, 400 km west of the Nile. The fossils occur at the same elevation at the ends of runoff channels north of Selima Oasis in Sudan. At 190 meters above sea level a smaller basin may have contained the lake as it shrank. Acheulian hand axes dating from the middle Pleistocene were found here.

Evidence points to mega-lakes also exiting in Chad, Sudan and Libya. The locations of these ancient oases could help explain migratory patterns of early humans.