Wah Wah Springs Caldera in Utah is an extinct volcanic caldera formed by a super-eruption about 30.06 million years ago during a prolonged volcanic episode in the Indian Peak–Caliente caldera complex. Identified in 2013, it is the largest known eruption center in that vast western U.S. volcanic field. The eruption produced an estimated 5,500 to 5,900 cubic kilometers of dacite and left ash-flow deposits, thick tuff, and a caldera about 1,000 square kilometers in area. Regarded as one of Earth’s largest known explosive eruptions, it shows how extraordinary volcanism once reshaped the interior American West long before the modern landscape emerged.