Which U.S. national park protects the world's largest gypsum dune field?

White Sands National Park in New Mexico protects the world’s largest gypsum dune field.

The park preserves about 115 square miles of a much larger, roughly 275-square-mile dune field in the Tularosa Basin. Unlike ordinary quartz sand, these brilliant white grains are gypsum, a soft mineral that normally dissolves in water and is therefore rarely found as extensive sand dunes.

The gypsum began accumulating when an ancient Permian sea left mineral deposits in the region. Later, the closed Tularosa Basin held Lake Otero, whose sediments supplied gypsum. As water evaporated, crystals formed; weathering broke them into sand, and strong winds moved the grains into the constantly shifting dunes seen today.

The area became White Sands National Monument in 1933 and was redesignated a national park in 2019. It is also known for unusual wildlife, including pale forms of animals that evolved camouflage against the white landscape. Great Sand Dunes National Park is a common mix-up, but its dunes are mainly quartz and rise beside Colorado’s Sangre de Cristo Mountains.