This photograph displays the two distinct parts of the world’s largest gypsum sand field, White Sands National Monument located in the Tularosa Basin in south-central New Mexico—the highly reflective eastern half, consisting of an assortment of gypsum dunes, and the western half, an alkali flat. Rain and snow from the San Andres Mountains and the Sacramento Mountains dissolve gypsum from the rocks and carry it to White Sands. The southwest corner of the monument, the lowest spot in the Tularosa Valley, changes from a dry lakebed into Lake Lucero when rain falls. The dark areas along the southern and eastern fringes of White Sands National Monument display low-growing vegetation that survives the ever-shifting gypsum sands.