Ridges formed by wind blown sand appear as watercolored streaks in this image from April 8, 1985, taken in the Erg Iguidi area of vast sand dunes across Algeria and Mauritania in northwestern Africa.
July 25, 2012 10:29 PM PDT
Photo by: NASA's Goddard Space Flight Center/USGS
| Caption by: James Martin
Conversation powered by Livefyre