Huge molten blob under Yellowstone found
Deep beneath Yellowstone National Park, one of the world’s most dynamic volcanic systems, lies an enormous, previously unknown reservoir of partly molten rock big enough to fill the Grand Canyon 11 times, scientists say.
Researchers on Friday said they used a technique called seismic tomography 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, steam vents and hot springs, sits atop a supervolcano that has had three calamitous past eruptions.
Scientists already knew of a large magma chamber under Yellowstone, which fed the eruptions 2 million, 1.2 million and 640,000 years ago. The new study, published in the journal Science, has 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,’’ University of Utah seismologist Jamie Farrell said.
‘‘However, these new findings do provide us, and other researchers, [with] the infor- mation needed to gain a better understanding of how magma moves from the mantle to the surface.’’
University of Utah geology and geophysics professor Fan-Chi Lin said the blob-shaped lower magma reservoir in Earth’s lower crust was 20-45 kilometres under Yellowstone, with a volume of 46,000 cubic km, or 11.2 times the volume of Arizona’s Grand Canyon. This magma chamber is filled with hot, mostly solid and spongelike rock with portions of molten rock within it.
The researchers said about 2 per cent of it was completely molten. The upper and lower magma chambers sit above a ‘‘plume’’ or upwelling originating in Earth’s mantle about 65km underground and transferring hot materials toward the surface.
Scientists had previously suspected that a lower magma chamber existed, but had been unable to confirm it.