Aerial views of Lenois Maranhenses from the SE corner of the dunes near Lagoa Bonita. Lenois 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 Lenois Maranhenses. The name means “bed sheets of Maranho Province”, as from above they resemble undulating sheets of pure white.