Ice cores from the Greenland Ice Sheet are helping researchers better understand past volcanic eruptions. © Michael Sigl
New studies of ice cores suggest that even small volcanic eruptions can have larger impacts worldwide than previously thought. Researchers in Greenland were able to detect ash from a historic eruption in the western United States.
Ice cores help to reconstruct weather conditions and the composition of the atmosphere in past centuries. However, trapped ash particles also provide information about previous volcanic eruptions. Scientists at the University of St Andrews in Scotland were now able to precisely date an eruption of the Newberry volcano and show that the ash spread more than 5,000 kilometers from Oregon on the west coast of the USA to Greenland.
The study used “geochemical fingerprinting” to identify ash particles in Greenland ice cores that came from the large shield volcano’s so-called “Newberry Pumice eruption.” The researchers also dated the outbreak to a period of two years around 686 AD.
The eruption is rated as a level 4 event on the Volcanic Explosivity Index (VEI). This made the eruption about ten times weaker than the eruption at Mount St. Helens in 1980 (VEI 5), but about ten times stronger than the eruption of Iceland’s Eyjafjallajökull in 2010 (VEI 3–4). What was particularly notable was not the intensity of the eruption, but rather that the ash spread across the United States and the Atlantic.
The results show that even comparatively small outbreaks can pose significant risks for the North Atlantic region – especially for air traffic on one of the world’s most used air routes. The Newberry volcano remains active and is classified by the US Geological Survey as a volcano with very high hazard potential; However, the eruption in 686 is the youngest known activity of this volcano.
Professor Andrea Burke from the University of St Andrews, who led the analysis of the ice cores, said: “This discovery was truly surprising to us. We would never have expected to find such large amounts of ash at such a great distance from a medium-sized eruption. This result powerfully highlights the usefulness of studying past volcanic eruptions in understanding today’s risks.”