The Jemez Caldera: A Supervolcano's Aftermath

The mountains to the west hold one of North America's most dramatic geological secrets. About one and a quarter million years ago, a tremendous eruption collapsed the ground into a massive caldera roughly fourteen miles across. Today that sunken crater is filled with a broad green valley called Valle Grande, a meadow so sweeping it looks like a stage set.

The Valles Caldera is now a national preserve, and the volcanic forces beneath it are not entirely spent. Geothermal energy still heats the rock below, and hot springs dot the landscape. The caldera's ash layers, called the Bandelier Tuff, spread across much of northern New Mexico and provided the material that ancestral Pueblo peoples carved into cliff dwellings on the Pajarito Plateau just to the east.