Virtual Field Trip—Group 3
Geology of White Sands National Monument
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Background Information
White Sands National Monument near Alamagordo, NM is located at the northern end of the Chihuahuan Desert in a mountain ringed valley called the Tularosa Basin. Rising from the heart of this basin is the world’s largest gypsum dune field. These dunes are geologically young. The wet climate during the last ice age (approximately 24,000–12,000 years ago) played a major role in its formation. The dunes are formed from ancient gypsum deposits that are dissolved from the local mountains and carried to shallow lakes. The gypsum remains because there is no drainage from the basin. As the seasonal lakes dry, the gypsum recrystallizes becoming selenite. The selenite erodes forming gypsum sand, which is carried by the wind and creates the dunes of White Sands.
