. A team of French and Mauritania researchers discovered that the Sahara Desert used to be flooded by a river. Satellites that are able to see below the Saharan Sands have detected an old riverbed, 320 miles in an area north of Africa with very few trees. If the ancient river existed, it would have been the 11th largest, in terms of how much water it could carry. Diagram of the major rivers in the Mediterranean, West African Tropical, and Equatorial Margins. Light blue is used to indicate the current Nile, Senegal and Niger rivers watersheds. Both the main course and outline of the Tamanrasett paleowatershed’s Tamanrasett are in light blue. Image: Nature Communications. USA Today quotes Peter deMenocal from Columbia University’s Lamont-Doherty Earth Observatory who describes the river network’s beauty as “monumental.” The study did not involve Mr. deMenocal. Mr. deMenocal said: “We have the smoking gun that this whole region – that today is without rainfall at any time during the year – supported a large, permanent system.” The Sahara was once a lush, green land Most of the Sahara Desert today, the world’s third largest desert after Antarctica and the Arctic, covering 9,400,000 square kilometers (3,600,000 square miles), is so hot and arid that virtually no plant life grows in it. However, about 10,000 years ago, the area was full of animals roaming the region’s lush grasslands. Human rock art indicates that the area was home to giraffes and a variety of other fauna. It was once quite different. Researchers have been able to prove that the Sahara Desert was once home to a river that ran thousands of miles across it. These rivers were connected by giant lakes which supplied water for lush green pastures and other fauna. Vast river networks Co-author, Charlotte Skonieczny of France’s University of Lille and IFRMER, and colleagues explained that the Sahara experienced a number of humid episodes during the late Quaternary (c. 12,000 years ago). There were large river networks during that time and increased freshwater supply to the ocean shores. The Western Sahara’s marine sediment records indicate that much of this material was transported there by rivers. Researchers believe that the Sahara’s West African margin had plenty of river water. The Japanese satellite captured radar images that the researchers used to find evidence of a missing river. The Phased Array typeL-band Synthetic Perturbation Radar (PALSAR), one of the Japanese Advanced Land Observing Satellite remote sensing instruments, was used. Radar detected traces of large waterways that were perfectly aligned with the canyon at the seafloor off the coast. Its path also coincides with that of the Tamanrasset which ran from modern Mauritania up to Algeria. Scientists are certain that an ancient river exists in the Sahara but they can’t date it. They suspect water was flowing along it from about 12,000 to 5,000 years ago. The area was once so green and fertile that it’s now known as “The Green Sahara”. Citation: “African dry periods triggered the reactivation a large river system within Western Sahara.” C. Skonieczny. P. Paillou. A. Bory. G. Bayon. L. Biscara. X. Crosta. F. Eynaud. B. Malaize. M. Revel. N. Aleman. -P. Barusseau, R. Vernet, S. Lopez & F. Grousset. Nature Communications 6, Article number 8751. November 10, 2015. DOI: 10.1038/ncomms9751. Video: The Sahara Desert was once a forest This Discovery video shows how the Sahara Desert was used to look like.
