It has enough magma inside to fill the Grand Canyon more than 11 times.
In 2004, scientists saw the ground above the caldera rise upward at rates as high as 2.8 inches due to a swelling magma reservoir four to six miles below the surface which is driving the uplift. The eruption of a “supervolcano” hundreds of times more powerful than conventional volcanoes – with the potential to wipe out civilization as we know it – is more likely than previously thought, a study has found.
Jean-Philippe Perrillat of the National Centre for Scientific Research in Grenoble has said that, “the difference in density between the molten magma in the caldera and the surrounding rock is big enough to drive the magma from the chamber to the surface” in a study, published in the journal Nature Geoscience
“The effect is like the extra buoyancy of a football when it is filled with air underwater, which forces it to the surface because of the denser water around it,” Dr Perrillat said.
“If the volume of magma is big enough, it should come to the surface and explode like a champagne bottle being uncorked.”
It has has long been known been know that shallow subsurface magma chamber, but now a second, much larger reservoir of partially molten rock has been discovered by researchers at the University of Utah which is 4 1/2 times larger. There’s enough magma inside, they say, to fill the Grand Canyon more than 11 times.
This image created by Eduardo Tarasca, shows a hypothetical but realistic 50x25x20 mile molten chamber sitting beneath Tokyo, Japan, that is identical to the one beneath Yellowstone National Park in the United States. “This supervolcano formation is capable of producing (240 cubic miles) of ash, rock, pumice and gas,” according to Tarasca.The force needed to achieve this is estimated to be the equivalent to 100,000 Hiroshima nuclear bombs. The last supervolcano eruption took place 26,000 years ago at Lake Taupo in New Zealand.
But the USGS isn’t that worried: “Yellowstone hasn’t erupted for 70,000 years, so it’s going to take some impressive earthquakes and ground uplift to get things started. Besides intense earthquake swarms (with many earthquakes above M4 or M5) we expect rapid and notable uplift around the caldera (possibly tens of inches per year). Finally, rising magma will cause explosions from the boiling-temperature geothermal reservoirs. Even with explosions, earthquakes, and notable ground uplift, the most likely volcanic eruptions would be the type that would have minimal affect outside the park itself.”