Valle Grande: Mouth of a Supervolcano

The enormous flat valley you can see from here is not a meadow carved by a river. It is the caldera of a supervolcano, formed about one and a quarter million years ago when colossal eruptions ejected a volume of material many times greater than the nineteen eighty eruption of Mount Saint Helens. When the magma chamber emptied, the land above simply collapsed inward, creating this bowl roughly thirteen miles across, now called the Valles Caldera.

For thousands of years the Pueblo peoples hunted this high grassland and quarried the obsidian that formed here in the volcanic heat. The caldera became a vast private cattle ranch in the late eighteen hundreds and stayed that way for over a century. In two thousand, Congress purchased it and created the Valles Caldera National Preserve, opening the ancient ground to the public for the first time in generations. What looks like a quiet mountain meadow holds one of the most violent geological events in New Mexico's deep past.