A new geological record of the Yellowstone supervolcano’s last catastrophic eruption is rewriting the story of what happened 630 000 years ago and how it affected Earth’s climate. This eruption formed the vast Yellowstone caldera observed today, the second largest on Earth. Two layers of volcanic ash-bearing the unique chemical fingerprint of Yellowstone’s most recent super-eruption have been found in seafloor sediments in the Santa Barbara Basin, off the coast of Southern California. These layers of ash, or tephra, are sandwiched among sediments that contain a remarkably detailed record of ocean and

climate change. Together, both the ash and sediments reveal that the last eruption was not a single event, but two closely spaced eruptions that tapped the brakes on a natural global-warming trend that eventually led the planet out of a major ice age. “We discovered here that there are two ash-forming super-eruptions 170 years apart and each cooled the ocean by about 3 °C (37.4 °F),” said U.C. Santa Barbara geologist Jim Kennett. Attaining the resolution to detect the separate eruptions and their climate effects is due to several special conditions found in the Santa Barbara Basin, Kennett said. READ MORE