Yellowstone could erupt more frequently than previously thought reports that the supervolcano beneath Yellowstone National Park in Wyoming recorded its last catastrophic eruption some 630,000 years ago, , forming a caldera that nearly spans the park’s width and belching a thick layer of ash, or tephra, buy ventolin online across North America. But rather than a single event, Yellowstone may have erupted twice in a span of 270 years, new evidence from mud cores discovered off the coast of Santa Barbara, California, indicates.