Yellowstone's Megavolcano is more than twice the beast we feared

Beneath Yellowstone National Park lurks a vast caldera – a high-pressure volcanic cauldron brimming with enough gas and magma to make Mount St. Helens' 1980-eruption look like a middle school science project by comparison. Now, newly reported findings suggest this megavolcanic reservoir is even bigger than previously believed. Much, much bigger.

Above: Grand Prismatic Spring, one of the many thermal springs heated by volcanic activity in Yellowstone National Park (credit: Douglas Faulkner/SPL).

The report, presented earlier this week at the American Geophysical Union Fall Meeting in San Francisco, is the second of its kind to emerge from the University of Utah this year. The first, delivered back in April, estimated that Yellowstone's magma reservoirs were "at least 50 percent larger than previously imagined." Now, seismologists have upped that estimate to a staggering 250%.

"We've been working [in Yellowstone] for a long time, and we've always thought it would be bigger," said seismologist and research team member Bob Smith in an interview with the BBC, "but this finding is astounding."

Measurements made by Smith and his colleagues led them to conclude that the caldera measures 55 miles long by 20 miles wide, and ranges anywhere between 1 to 9 miles deep along its length. With those dimensions, the researchers say the magma chamber is likely to contain upwards of 150 cubic miles of molten rock.

"To our knowledge there has been nothing mapped of that size before," said researcher Jamie Farrell, who presented the team's 50% estimate back in April.

The good news, say the researchers, is that a larger reservoir does not necessary increase the odds of the caldera erupting. As for when Yellowstone's mega volcano will blow, the last three major eruptions took place 640,000, 1.3-million, and 2.1 million years ago – so some say we're about due for another cataclysmic eruption.

Farrell, for one, doubts a blast will occur in the immediate future. For one thing, he says, "we have a whole system of monitoring equipment [at Yellowstone]... and we believe if there was going to be an eruption we would have advance warning that magma was moving beneath the surface."

One thing, Farrell says, is for certain: a large-scale eruption of the Yellowstone caldera would be cataclysmic on an unprecedented scale. "Nobody's ever witnessed one of these large supervolcanic eruptions," he said, noting that previous examples are believed to have been 2,000-times the size of Mount St. Helens' 1980 eruption.

"It would affect the world," said Farrell. "All the material that is shot up into the atmosphere [during an eruption] would eventually circle the Earth and affect the climate throughout the world."

Read more at the BBC.