This astronaut photograph shows classic large and small sand masses of the central Sahara Desert, where wind is a more powerful land-shaping agent than water.
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.
White sand dunes spill across the Snake River Plain in a wide arc in this detailed, photo-like image acquired by the Advanced Land Imager on NASA’s EO-1 satellite on September 25, 2010.
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.
The Ar Rub’ al Khali, or Empty Quarter, covers much of the south-central portion of the Arabian Peninsula and is the largest continuous sand desert on Earth.