Dunes, Lenšˇis Maranhenses National Park, Brazil
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 Lenšˇis 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.
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.
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