The Yellowstone caldera spreads beneath the states of Wyoming, Montana and Idaho and gets its nickname as a supervolcano due to its ability to inflict devastation on a global level. It is constantly monitored by the United States Geological Survey (USGS) for signs that a supereruption is on its way, something that has only happened three times in history, 2.1 million years ago, 1.3 million years ago and 640,000 years ago, leaving some to claim a massive eruption is overdue. eUntil 2017, geologists thought it would take centuries for the supervolcano to undergo a critical change before an eruption, but after analysing minerals in fossilised ash from the most recent eruption, researchers at Arizona State University found the supervolcano last awoke after two influxes of fresh magma flowed into the reservoir below the caldera.
The minerals revealed that the critical changes in temperature and composition built up in a matter of decades, not centuries.
Graduate student Hannah Shamloo said: “It’s shocking how little time is required to take a volcanic system from being quiet and sitting there to the edge of an eruption.”
Christy Till, a geologist at Arizona State, and Ms Shamloo’s dissertation adviser, added: “We expected that there might be processes happening over thousands of years preceding the eruption.”
Kari Cooper, a geochemist at the University of California, said Ms Shamloo and Dr Till’s research offered more insights into the time frames of supereruptions, but said more research needs to be done.
She added: “It’s one thing to think about this slow gradual build-up — it’s another thing to think about how you mobilise 1,000 cubic kilometres of magma in a decade.”
A 2013 study showed the magma reservoir that feeds the caldera was about two-and-a-half times larger than previously estimated.
Scientists thought this was drained out by every blast and took a long time to refill, but the new study suggests the situation can change far quicker.
However, the USGS has previously put minds at ease regarding any “overdue” claims.
Yellowstone Volcano Observatory’s Scientists-in-Charge Jacob Lowenstern said in 2014: “When you see people claiming it’s overdue, usually the numbers they come up with say the last eruption was 640,000 years ago, but it erupts every 600,000 years.
“But, in fact, if you average the eruption intervals, there’s 2.1 million to 1.3 million and then another 640,000 years ago.
“If you average those numbers you come up with something that’s over 700,000 years.
“So, in reality, even if you tried to make this argument, it wouldn’t be overdue for another 70,000 years.”
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Dr Lowenstern even went on to question this calculation’s validity.
He added: “The other thing that is important to realise is that when they do statistics based on two eruptive intervals, they are just playing games.
“Because we don’t know. There’s no clock down there, the magma is going to erupt when it wants to erupt.
“There’s been a lot of things that have happened over the last 600,000 years that might indicate there’s less likelihood of an eruption.”