Do you know that the story of the major attraction at White Sands National Monument began about 250 million years ago? At that time, the land was below sea level, covered by shallow marine waters laden with minerals. Many of these, including gypsum, became part of the ocean floor that eventually turned to rock.
The area rose later, and a giant dome that included layers of these rocks formed in the region. About 10 million years ago, the central portion sank to form the Tularosa Basin, leaving the dome edges as the San Andres and Sacramento mountains. Weathering in these mountain areas is slowly re-dissolving the minerals, which are being carried into the basin by the scanty precipitation.
With no outlet from the bolson, these gypsum-bearing waters slowly
evaporate, forming crystals of nearly pure gypsum. Eventually these crystals break up
to form sand—sand that is carried by the southwesterly winds to form the dune
fields of White Sands.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
A gypsum dune at White Sands National Monument, New Mexico. Photograph by A. H. Harris.