Search for stock images of the desert, and you’ll find countless versions of a single scene: sand dunes. Our region certainly has its dune fields: the Samalayuca Dunes near Ciudad Juárez, the Monahans Sandhills, the Salt Basin Dunes at Guadalupe Mountains National Park, and New Mexico’s famous White Sands. But dunes are only a tiny portion of the Chihuahuan Desert.
And, yet, they do embody an essential truth. More than mountains, mesas or canyons, they distill the desert’s defining phenomenon: drought.
Dr. Richard “Rip” Langford is a UTEP geology professor.
“I'm a fourth-generation El Pasoan,” Langford said, “and I love the desert. It's home. And so when I started into my research, I started focusing on desert environments. There weren't many people studying deserts at that time, so it was a great opening.”
Langford has long studied sand dunes, including New Mexico’s White Sands, the largest gypsum dune field in the world.
White Sands has recently been in the news for its fossilized footprints of Ice Age beasts — mammoths, ground sloths, camels — and Ice Age people. The prints were made beside an immense lake, bounded by piñon pines. It’s a reminder of how much wetter the Ice Age Southwest was.
But as the glaciers receded, the region’s climate was transformed. The lake evaporated. In a process called deflation, westerly winds — like those present-day West Texans know all too well — scoured the lake bed.
Around 7,000 years ago, the region witnessed an extended drought. Winds began to excavate soft white gypsum that had collected in the Ice Age lakebed.
“And it looks like that these deflation events were very sharp, very sudden things,” Langford said, “and I've always imagined them as being during hyper-arid super-droughts. So it didn't rain for 50 years.”
Geologists typically deal in vast sweeps of time. But the development of the dunes was swift. Winds blew gypsum east from the lakebed, piling it up. Much of the dune field visitors see today, Langford said, was created within 400 years.
There were additional dune-building episodes, as mega-droughts hit the Southwest 4,000 years ago, and 2,000 years after that.
The same process unfolded just west of the Guadalupe Mountains, Langford said, creating Texas’s Salt Basin Dunes.
White Sands visitors can see that the most easterly dunes, near the visitors center, are blanketed in vegetation. To the west, the dunes are stark and bare. Far from the ancient lakebed’s salty groundwater, the eastern dunes capture and retain rainwater. That supports vegetation, which in turn holds the dunes in place.
It explains why the dune field is most active near the dry lakebed, Langford said.
“It's called the main dune ridge,” he said. “It's about kilometer, a kilometer and a half along the western edge of the dune field. And that's where sand blowing out of the sand flat is accumulating, and that's where the tallest dunes are, and the most rapidly moving dunes.”
White Sands and the region’s other “sand seas” aren’t only a recent development. They’re also an evolving one. Climate change is likely to drive new dune-building in the years to come, Langford said.
“We're going to be looking at more and more severe droughts, more and more heavy flood events,” he said. “I can see a new episode of dune construction. It’s going to be a dynamic period, and one that's going to be pretty tough on us.”
In the span of a few millennia, distinctive plants have adapted to grow in the dunes. Multiple lizard species have developed “blanched” or “bleached” forms to thrive in the white sands.
Our region’s dune fields embody both harsh desert realities, and the resilience of desert life.
