What with all the bison and bears and wolves and tourist campers perambulating above the chamber of hot, partly molten rock that lies below Yellowstone National Park and powers those geysers, it might be nice to know when the area's supervolcano - which we've known about for a long time -- will awaken and erupt again. And although no eruption has occurred in nearly70,000 years, many wonder when the next one might hit. There may be a way to predict just that, according to Arizona State University researchers, who recently published their findings in the journal Geology. Maybe more importantly, they also say they think the next eruption won't be cataclysmic.

It's first important to keep this in mind: "We find that the last time Yellowstone erupted after sitting dormant for a long time, the eruption was triggered within 10 months of new magma moving into the base of the volcano, while other times it erupted closer to the 10 year mark," says petrologist Christy Till, of ASU, in a release.

The researchers examined the volcano's distant past combined with advanced microanalytical techniques. She and colleagues used measurements from a NanoSIMS ion probe -- a type of ion microprobe used for elemental and isotopic analysis of ultra-fine features - to document very sharp chemical concentration gradients in magma crystals. Those allowed calculation of the magma's timescale between reheating and eruption, a release said.

If magma moves into the crust, the countdown clock would start ticking--but there would be some notice, as Yellowstone is monitored by instruments that can detect precursors to eruptions, such as earthquake swarms caused by magma moving, a release reported.

If magma doesn't erupt, it sits in the crust and slowly cools to form crystals. Over thousands of years, the last bit of this magma will crystallize, unless it reheats and reignites another eruption, as a release stated.

The researchers' central question was, according to a release: "How quickly can you reheat a cooled magma chamber and get it to erupt?"

They are still working on that information, but using the NanoSIMS, they analyzed crystal samples from lava flows. Scientists can read crystals' magma chambers, which grow zones like tree rings and show history and environmental changes, the release noted.

From this history, they note that in one case an eruption occurred within 10 months after reheating a mostly crystallized magma reservoir following a 220,000-year period of volcanic quiescence, saysTill, in one release. "A future eruption could occur over similar timescales." 

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