The three largest gypsum dune fields in the world are located in the Chihuahuan Desert. White Sands National Monument in New Mexico protects a portion of the largest dune field, the second largest field is located in Cuatro Cienegas in the Mexican state of Coahuila, and the third largest is in Guadalupe Mountains National Park in Texas.
It is unusual to find gypsum in the form of sand because it dissolves in water. Chihuahuan Desert dune fields are located in closed basins—meaning water does not flow out of the basins. Water sinks into the ground or forms shallow pools that dry out under the desert sun, leaving behind the gypsum crystals that break down into sand when exposed to the weather. Strong prevailing winds push the sand into dunes that constantly change shape as they move downwind. Vegetation and water stabilize the dunes.
We monitor dunes using repeated LiDAR (Light Detection and Ranging) surveys. Vegetation and groundwater monitoring occurs along with dune monitoring to help clarify the potential cause and effect relationships between dune activity, vegetation, and the shallow water table. This information helps White Sands National Monument park managers understand how changing climate and large-scale groundwater withdrawal projects in the region may affect dune field integrity. Because the dune field lies in an area once occupied by ancient lakes, LiDAR sampling may also help determine erosion rates for paleontologically-rich shoreline deposits and locate and monitor unique archaeological gypsum hearth mounds.