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Ancient dunes

The sand dunes on the banks of the São Francisco River, the most extensive inland dunes in Brazil, began to form more than 20,000 years ago. Researching how they were created in the Xique-Xique region of Bahia, geologist Patricia Mescolotti assigned different colors to different altitudes on radar images obtained by NASA. In this image of the Grande and São Francisco rivers, altitudes of 400 to 425 meters are highlighted in yellow, and the riverbanks are shown in orange and brown. Beside a nearby lake, marked in dark green, is a dune field that reaches altitudes of up to 450 meters. Remote sensing techniques can be used to analyze the terrain and select the best locations to collect samples for dating.

Image submitted by Patricia Mescolotti, a PhD student at São Paulo State University (UNESP) in Rio Claro