Strong winds blowing in from the Western Atlantic sculpt the sand along the coast into distinctive crescent shapes.
Published Oct 16, 2017
Sand dunes sprawl along the coast of northeastern Brazil, sometimes extending kilometers inland.
Published Jul 11, 2010
The area shown here (10 kilometers across) is a small part of the dune field which is now protected as the Len&ccelde;óis Maranhenses National Park, on Brazil’s north coast, about 700 kilometers east of the Amazon River mouth. Persistent winds blow off the equatorial Atlantic Ocean onto Brazil from the east, driving white sand inland from the 100 kilometer stretch of coast (upper margin of the image), to form a large field of dunes. The strongly regular pattern of these dunes is a common characteristic of dune fields. The basic shape of each sand mass, repeated throughout the view, is a crescent-shaped dune. In an area with a rich supply of sand such as coastal Brazil, individual crescents coalesce to form entire chains many miles long. The wind strength and supply of sand are sufficient to keep the dunes active, and thus free of vegetation, despite 1500 mm (60 inches) of rainfall annually. The dark areas between the white dunes are fresh water ponds that draw fisherman to this newly established park.
Published Oct 20, 2003
Large linear dunes stretch across the Great Eastern Sand Sea of northern Algeria.
Published Apr 4, 2016
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.
Published Oct 3, 2005
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.
Published Sep 11, 2006
This digital elevation map of the Badain Jaran Desert shows multi-generation dunes, with smaller dunes resting atop larger ones.
Published Apr 20, 2011
Fans of the Star Wars series of films may recognize the Algodones Dunefield—also known as the Imperial Dunes—as portions of the imaginary planet of Tatooine. While not planetary in scale, this dunefield located at the junction of three states (Arizona and California in the United States; Baja California del Norte in Mexico) is a distinctive feature of North America. The field is approximately 72 kilometers long by 10 kilometers wide (45 miles by 6 miles) and extends along a northwest-southeast line that correlates to the prevailing northerly and westerly wind directions. The dune field is a wilderness area, with the only human structure being the All American Canal that cuts across the southern portion from west to east (right side of view). A checkerboard pattern of farms in the Colorado River flood plain is visible on the Mexican side of the border (far right). Wisps of cloud obscure the Cargo Muchacho Mountains (top).
Published Nov 21, 2005
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.
Published Feb 7, 2005
This detailed true-color image from February 24, 2011, shows the variety of sand dunes that make up the Algodones Dunes in southeastern California.
Published May 27, 2011
Complex wind patterns left these distinctive star-shapes in the sands of the Grand Erg Oriental.
Published Sep 29, 2013
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