File:Dual Marvels of New Mexico (MODIS).jpg

English: The glistening patch of white tucked in southern New Mexico’s Tularosa Valley marks the Earth’s largest gypsum dune field, most of which is protected as White Sands National Park. On April 29, 2023, the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image encompassing not only White Sands National Park but also the dark Carrizozo Malpaís Lava Flow.

Gypsum is a common mineral found in sedimentary rocks (rocks formed from layer upon layer of sediment laid down by wind or water), but it is extremely rare that gypsum forms sand dunes. The Tularosa Valley is a basin sitting between two mountain ranges which are rich in sedimentary rocks. Over time, as rain washed over the mountains it dissolved the gypsum and carried it to the lowest part of the basin, where it collected in a playa known as Lake Lucero. Eventually the intense heat in the northern Chihuahuan Desert evaporated most of the water in the basin, leaving behind crystalline gypsum (selenite), which then was carried by the wind to form great undulating, bright white sand dunes that span about 275 square miles (710 square kilometers).

The forces that created the black basaltic rock of the Carrizozo Malpaís Lava Flow, north of White Sands, were entirely different than the action of water and wind that created the gypsum dunes. Little Black Peak, an inactive cinder cone located at the northern end of Carrizozo Malpaís, is the highest point on the larger shield volcano. Approximately 5,000 years ago, a vent erupted at Little Black Peak and lasted several decades. The event created the second youngest lava flow in New Mexico and one of the longest flows from the Holocene Epoch. From its northernmost to southernmost points, the it stretches 50 miles (75 kilometers) across the Chihuahuan Desert.