Deep in Greenland's ancient ice, researchers at the University of St Andrews found something extraordinary: microscopic ash particles from an eruption that occurred 1,338 years ago in Oregon, a volcanic plume that traveled more than 5,000 kilometers across the globe. The discovery, published in Quaternary Science Reviews, reveals that Newberry Volcano's eruption in 686 AD—a relatively modest event by volcanic standards—spread its ash far beyond what scientists previously thought possible for an eruption of its size.
This matters because it fundamentally changes how we understand volcanic risk across the Northern Hemisphere. The ash particles, each just 0.02 millimeters in size, were located in ice cores drilled during international campaigns in Greenland. By matching the chemical fingerprint of these particles to deposits from Newberry Volcano in the Cascade Range, researchers were able to pinpoint the eruption's timing to within two years of 686 AD—a precision far greater than earlier estimates that had narrowed it to a 140-year window around the turn of the 7th Century.
Dr. Helen Innes, lead author from the School of Earth and Environmental Sciences at the University of St Andrews, described the moment of identification: "When we find tiny ash fragments in the ice core, it can be really challenging to trace them to their precise volcanic source. So it was a really exciting moment when we compared the geochemical fingerprint to Newberry and it was an exact match."
The Newberry eruption ranks as a VEI 4 event on the Volcanic Explosivity Index—about 10 times smaller than Mount St Helens' catastrophic 1980 eruption and roughly equivalent in scale to the 2010 Eyjafjallajökull eruption in Iceland. Eruptions of this magnitude occur several times each decade globally, making them relatively common. Yet what made Newberry exceptional was the sheer distance its ash traveled and the quantity that crossed the Atlantic to deposit in Greenland. Scientists believe powerful winds at the time of eruption helped transport the fine ash particles across North America and eastward.
The implications are sobering. The North Atlantic is among the world's busiest flight corridors, and finding such abundant ash from a relatively minor eruption in Greenland demonstrates that size alone doesn't determine a volcano's global reach. A smaller but ash-rich eruption in an active region could cause widespread disruption far from its source—disruption that might rival what Eyjafjallajökull caused European airspace in 2010.
Newberry Volcano itself remains active and is classified as having "very high threat potential" by the U.S. Geological Survey National Volcano Early Warning System. It sits in the Cascade Volcanic Range, the same geologically restless region that produced Mount St Helens. While researchers studying past eruptions see that ash deposited close to the volcano forms a narrow, elongated pattern—evidence of those strong eruption-time winds—the broader lesson is that North America, Russia, and Japan host "huge numbers of volcanoes" capable of spreading ash across the Northern Hemisphere, as Dr. William Hutchison from St Andrews noted.
For disaster response planners and international aviation authorities, the discovery underscores an uncomfortable truth: predicting when and where the next globally disruptive eruption will strike remains nearly impossible. What's increasingly clear is the need for governments and international agencies to coordinate their readiness now, before a volcano reminds us just how fragile the assumption of stability really is.