Coastal Dunes, Lençóis Maranhenses National Park, Brazil

High-resolution image (1.6 Mb)

The area shown here, 10 kilometers (6 miles) across, is a small part of the dune field which is now protected as the Lençóis Maranhenses National Park, on Brazil's northern coast, about 700 kilometers (435 miles), east of the Amazon River mouth. Persistent winds blow off the equatorial Atlantic Ocean onto Brazil from the east, driving white sand inland from a 100 kilometer (62 mile) stretch of coast, to form a large field of dunes. The strong regular pattern of dunes is a 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 1,500 millimeters (60 inches) of rainfall annually. The dark areas between the white dunes are fresh water ponds that draw fisherman to this newly established park.

The characteristic regularity of the dune landscape can be detected downwind for more than 100 kilometers (62 miles), beyond the present dune field. Now covered by dense forest, the greater extent of this dune field indicates that climates have been substantially drier at the Equator in the recent geological past.

Astronaut photograph ISS007-E-15177 was provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. The International Space Station Program supports the laboratory to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth.