(CNN) As tourists stroll between Yellowstone’s 300 active geysers, taking selfies in front of thousands of bubbling, boiling mud pots and hissing steam vents, they are treading on one of the planet’s greatest time bombs.
The park is a supervolcano so enormous, it has puzzled geophysicists for decades, but now a research group, using seismic technology to scan its depths, have made a bombshell discovery.
Yellowstone’s magma reserves are many magnitudes greater than previously thought, say scientists from the University of Utah.
Underneath the national park’s attractions and walking paths is enough hot rock to fill the Grand Canyon nearly 14 times over. Most of it is in a newly discovered magma reservoir, which the scientists featured in a studypublished on Thursday in the journal Science.
It may help scientists better understand why Yellowstone’s previous eruptions, in prehistoric times, were some of Earth’s largest explosions in the last few million years.
Fire in Earth’s belly
Yellowstone’s ultimate heat source reaches down 440 to 1,800 miles beneath Earth’s surface — and may come from its molten core. It is responsible for fueling the newly discovered reservoir that lies on top of it.
The magma chamber, which scientists already knew about, lies on top of the reservoir — and draws magma from it. It is a three to nine miles under the surface of the Earth and is what fuels the geysers, steaming puddles and other hot attractions.
It alone has a volume 2.5 times that of the Grand Canyon.
But those great magma expanses do not mean that the two hellish hollows could overflow the Grand Canyon with molten rock.
No new dangers
The overwhelming bulk of their magma cavities comprise scorching — yet solid — rock, which is hollow, like sponges, and filled with pockets of liquefied rock.
Also, the discovery doesn’t mean that there is now more magma than there was before, the scientists say. And they are no signs of an imminent eruption.
“The actual hazard is the same, but now we have a much better understanding of the complete crustal magma system,” said researcher Robert B. Smith.
An eruption in the next few thousand years is extremely unlikely, the USGS says. The Utah scientists put the yearly chance at 1 in 700,000 — about the odds that you will be struck by lightning.