Sand sheets show chevrons



In Saharan Africa, sand sheets stretch in virtually flat expanses for hundreds of kilometers. The sheets have been considered devoid not only of life but of regional landforms that might provide insight into the wind-driven processes of erosion and transport by which deserts sustain themselves and grow. Now a fresh, computer-enhanced look at satellite images of sand sheets in Egypt and Sudan by Ted Maxwell of the Smithsonian Institution's Center for Earth and Planetary Studies (Washington, D.C,) and C. Vance Haynes of the University of Arizona (Tucson) has led to the discovery of huge, flat sand dunes.