Deep reservoirs of "dark" magma may be feeding volcanoes in places like Yellowstone National Park and Hawaii, locations far from the usual "ring of fire" tectonic plate boundaries where such volcanoes are common, a new study suggests.
Such deep underground pockets of red-hot molten rock could be siphoning energy from Earth's core to create volcanoes where we might not otherwise expect them, say researchers at the Carnegie Institution for Science in Washington, D.C.
Geophysicist Alexander Goncharov and his colleagues suggest in the journal Nature Communications that there may be patches of older, "dark" magma -- remnants of a very early molten phase in Earth's history -- lying just above our planet's outer core.
Pressures and temperatures that far below the Earth's surface -- some 1,800 miles down -- are so extreme they could be creating magma with different atomic structures than magma from shallower depths under less pressure, they suggest.
Patches of such magma could be soaking up heat from the Earth's core, acting as doors to pass that heat by convection into the mantle, creating magma that rises up in a massive hot plume to create volcanoes in unexpected places like Yellowstone, Hawaii, Easter Island and even Mount Etna in Italy.
Although not located near the edge of any tectonic plates, millions of years in the past such "hot spot" volcanoes poured forth so much lava they covered entire continents with molten rock.
If the researchers are right about what drives such volcanoes, other experts say, it could yield insights into an important part of the geology of the Earth -- its magnetic field.
Because the transfer of heat inside our planet powers many of its processes, including how its core spins and flows inside the Earth, "the way heat flows from the core to the mantle could potentially affect the way Earth's magnetic field evolves over time," says Thomas Duffy, a Princeton University geoscientist not involved with the study.
Not everyone is willing to accept the "dark magma" theory, suggesting that until scientists can perform experiments with molten rock at temperatures of 5,600 degrees Fahrenheit, no one can be sure of exactly how magma actually behaves.
Duffy agrees, but says the Carnegie work merits close examination.
"It's a very provocative paper ... a bit speculative," he acknowledges. "But it's taking us in an important step on the road to understanding the deep Earth."
