Ms. Shamloo later analyzed trace crystals in the volcanic leftovers, allowing her to pin down changes before the supervolcanoâs eruption. Each crystal once resided within the vast, seething ocean of magma deep underground. As the crystals grew outward, layer upon layer, they recorded changes in temperature, pressure and water content beneath the volcano, much like a set of tree rings.
âWe expected that there might be processes happening over thousands of years preceding the eruption,â said Christy Till, a geologist at Arizona State, and Ms. Shamlooâs dissertation adviser. Instead, the outer rims of the crystals revealed a clear uptick in temperature and a change in composition that occurred on a rapid time scale. That could mean the supereruption transpired only decades after an injection of fresh magma beneath the volcano.
The time scale is the blink of an eye, geologically speaking. Itâs even shorter than a previous study that found that another ancient supervolcano beneath Californiaâs Long Valley caldera awoke hundreds of years before its eruption. As such, scientists are just now starting to realize that the conditions that lead to supereruptions might emerge within a human lifetime.
âItâs shocking how little time is required to take a volcanic system from being quiet and sitting there to the edge of an eruption,â said Ms. Shamloo, though she warned that thereâs more work to do before scientists can verify a precise time scale.
Dr. Kari Cooper, a geochemist at the University of California, Davis who was not involved in the research, said Ms. Shamloo and Dr. Tillâs research offered more insights into the time frames of supereruptions, although she is not yet convinced that scientists can pin down the precise trigger of the last Yellowstone event. Geologists must now figure out what kick-starts the rapid movements leading up to supereruptions.
âItâs one thing to think about this slow…