The dunes at White Sands come in four primary types: dome, barchan, transverse, and parabolic. Illustration by Jameson Simpson.
WIND CARVES THE CHARACTER OF the dunes at White Sands, generally driving them from the southwestern corner of the park to its northeastern edge. Seasonal fronts can bring wind from the north and, occasionally, from the southeast. That makes for perpetual work for the plow drivers who clear the roads of moving sand.
“By and large it’s the winds that shape the dunes,” says Ryan Ewing, an associate professor of geology at Texas A&M University who has studied dune formation and movement at White Sands. The dominant wind sculpts the dunes to generally orient with those prevailing winds. “That gives you that nice, sinuous crest line.”
- The dunes are, essentially, born on the edge of the park’s Lake Lucero, where they emerge in toe-high piles of sand.
- The dunes are made of gypsum, from a geologic formation 260 million years old, created when the Southwest was covered by shallow seas. Unlike the more common quartz sand, gypsum sand grains have a more angular, elongated shape—not unlike the dunes themselves.
- Dunes come in four primary types. Dome dunes are smaller and faster-moving. They form closer to the edge of Lake Lucero and can move at almost four times the average speed of the rest of the dune field. Barchan dunes are thickest around the middle. Barchan and transverse dunes, which line up in tall mounds nestled next to one another, dominate the White Sands dune field. Parabolic dunes form in archlike shapes, bent by the vegetation that holds parts of them in place, and crawl at just two to eight feet a year.
- Researchers are using new geophysical techniques to map and track the dunes over time. Those records show them migrating about 10 feet each year on average. They also show dunes growing “arms,” Ewing says, that essentially reach out and hit one another; sometimes the larger dune swallows the smaller ones.