Aerial views of Lençois Maranhenses from the SE corner of the dunes near Lagoa Bonita.
Lençois Maranhenses National Park is a coastal dune field (measuring some 155,000 hectares) that is flooded with fresh water lakes during the January to May rainy season. Strong prevailing winds from the East mobilize the barchan dunes during the dry season and, combined with the equatorial sun, evaporate the lakes and prevent permanent vegetation from taking root. The dunes are composed of quartz grains that are eroded from the granite and washed down from the Parnaiba River and then carried north by ocean currents before being deposited on the coast of Lençois Maranhenses. The name means "bed sheets of Maranhão Province", as from above they resemble undulating sheets of pure white.
Lençóis Maranhenses National Park in northeast Brazil is too rainy during the wet season to be considered a desert. A rock layer beneath the sand, which prevents rain water from filtering down, forms pools and lagoons of crystal clear water.
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