Deep beneath Yellowstone National Park, one of the world’s most dynamic volcanic systems, lies an enormous, previously-unknown reservoir of hot, partly-molten rock big enough to fill up the Grand Canyon 11 times, scientists say.
Researchers said they used a technique called seismic tomo-graphy to produce for the first time a complete picture of the volcanic “plumbing system” at Yellowstone, from the Earth’s mantle up to the surface.
Yellowstone, which straddles the borders of Wyoming, Idaho and Montana and boasts a remarkable array of geothermal features including geysers, mudpots, steam vents and hot springs, sits atop a super-volcano that has had three calamit-ous past eruptions.
Scientists already knew of a large magma chamber under Yellowstone that fed the eruptions two million, 1.2 million and 640,000 years ago.
The new study, published in the journal Science, revealed a second, deeper reservoir 4.5 times larger.
“The existence of the second magma chamber does not make it any more or less likely that a large volcanic eruption at Yellowstone will occur. These findings do not change the current volcanic hazard at Yellowstone,” University of Utah seismologist Jamie Farrell said. “However, these new findings do provide us and other researchers the information needed to gain a better understanding of how magma moves from the mantle to the surface.”
The existence of the second magma chamber does not make it any more or less likely that a large volcanic eruption at Yellowstone will occur
University of Utah geology and geophysics professor Fan-Chi Lin said the blob-shaped lower magma reservoir in Earth’s lower crust is located 19 to 45km under Yellowstone, with a volume of 11,500 cubic miles, or 11.2 times the volume of Arizona’s Grand Canyon.
This magma chamber is filled with hot, mostly-solid and sponge-like rock with portions of molten rock within it. The researchers said about two per cent of it is completely molten.
The upper and lower magma chambers sit above a ‘plume’, or upwelling, originating in Earth’s mantle about 40 miles underground and transferring hot materials towards the surface. Scientists had previously suspected that a lower magma chamber existed, but until now had been unable to confirm it.
The researchers said the technique they used, seismic tomo-graphy, is analogous to a CT scan of the body.
They were using seismic waves as they travel throughthe Earth to image the subsurface, distinguishing between rock layers of various densities.
They said they also combined both local and distant earthquake measurements to image Yellowstone’s complete magma system.