One of the main reasons that rainless regions like the Sahara Desert are interesting from the perspective of landscape science is that the work of flowing water—mainly streams and rivers—becomes less important than the work of wind. Over millennia, if enough sand is available, winds can generate dunes of enormous size, arranged in regular patterns. Long, linear dunes stretch generally north to south across much of northeast Algeria, covering a vast tract (~140,000 square kilometers) of the Sahara Desert known as the Erg Oriental. Erg means “dune sea” in Arabic, and the term has been adopted by modern geologists. Spanning this image from a point on the southwest margin of the erg (image center point: 28.9°N 4.8°W) are a series of 2-kilometer-wide linear dunes, comprised of red sand. The dune chains are more than 100 meters high. The “streets” between the dunes are grayer areas free of sand.
he Issaouane Erg (sand sea) is located in eastern Algeria between the Tinrhert Plateau to the north and the Fadnoun Plateau to the south. Considered to be part of the Sahara Desert, the Issaouane Erg covers an area of approximately 38,000 km2. These complex dunes form the active southwestern border of the sand sea.
The combination of stable, ancient dunes and water channels displaying both braided and cross-connecting patterns make this region a planetary analogue for Mars.
This photograph taken by an astronaut on the International Space Station highlights a sand dune field within the Burqin-Haba River-Jimunai Desert near the borders of China, Mongolia, Russia, and Kazakhstan.
This detailed view of the remote Conception Bay sector of the Namibian coastline shows breakers and a strand plain on the left and complex dunes of the Namib dune sea on the right. A strand plain is a series of dunes, usually associated with and parallel to a beach, sometimes containing small creeks or lakes. The complexity and regularity of dune patterns in the dune sea of the Namib Desert have attracted the attention of geologists for decades; however, they remain poorly understood. The flat strand plain (roughly 4 kilometers shown here) shows a series of wet zones that appear black where seawater seeps inland and evaporates. These patches are aligned with the persistent southerly winds, some of the strongest of any coastal desert.