Ten thousand years ago, as the last Ice Age was ending and temperatures rose, an enormous glacial lake in New Mexico’s Tularosa Basin dried up, revealing something unusual: bright-white gypsum sand.

Because gypsum ... sand. The entire dune field is a massive 275 square miles (by comparison, the second-largest gypsum dune field in the world, Cuatro Ciénegas in Mexico, is only 8 square miles).

A national monument until 2019, White Sands National Park is home to the largest gypsum dune field in the ... once underwater of the 1,600-square-mile Lake Otero, which dried up 10,000 years ...

These marks were found in the dried mud of an ancient lake in White Sands National Park ... of two major geomorphological components: a gypsum dune field from the Late Pleistocene or Holocene ...

Fossilized footprints, preserved in gypsum ... White Sands is to point the way to a new archive of evidence.” The footprints were made by people walking on damp ground at the edge of a lake.