The
gorgeous colors of Yellowstone’s Grand Prismatic hot spring are among
the national park’s myriad hydrothermal features created by the
Yellowstone supervolcano. A new University of Utah study reports
discovery of a huge magma reservoir beneath Yellowstone’s previously
known magma chamber. (“Windows into the Earth,” Robert B. Smith and Lee
J. Siegel)
Yellowstone National Park is the home of one
of the world's largest volcanoes, one that is quiescent for the moment
but is capable of erupting with catastrophic violence at a scale never
before witnessed by human beings. In a big eruption, Yellowstone would
eject 1,000 times as much material as the 1980 Mount St. Helens
eruption. This would be a disaster felt on a global scale, which is why
scientists are looking at this thing closely.
On Thursday, a team
from the University of Utah published a study, in the journal Science
that for the first time offers a complete diagram of the plumbing of the
Yellowstone volcanic system.
The new report fills in a missing
link of the system. It describes a large reservoir of hot rock, mostly
solid but with some melted rock in the mix, that lies beneath a shallow,
already-documented magma chamber. The newly discovered reservoir is
4.5 times larger than the chamber above it. There's enough magma there
to fill the Grand Canyon. The reservoir is on top of a long plume of
magma that emerges from deep within the Earth's mantle.
[Geysers erupt because they’re all bendy inside]
This
system has been in place for roughly 17 million years, with the main
change being the movement of the North American tectonic plate, creeping
at the rate of roughly an inch a year toward the southwest. A trail of
remnant calderas can be detected across Idaho, Oregon and Nevada,
looking like a string of beads, marking the migration of the tectonic
plate. A similar phenomenon is seen in the Hawaiian islands as the
Pacific plate moves over a hot spot, stringing out volcanoes, old to
new, dormant to active.
University
of Utah seismologists funded by the National Science Foundation found a
pool of magma beneath Yellowstone's supervolcano that they say is big
enough to fill the Grand Canyon more than 11 times. (National Science
Foundation/University of Utah)
“This is like a
giant conduit. It starts down at 1,000 kilometers. It's a pipe that
starts down in the Earth," said Robert Smith, emeritus professor of
geophysics at the University of Utah and a co-author of the new paper.
The lead author is his colleague Hsin-Hua Huang.
This new picture
doesn't change, fundamentally, the risk assessment of Yellowstone, but
it will help scientists understand the mechanics of the volcano.
“Really
getting an idea of how it works and understanding how these large
caldera-forming eruptions may occur, and how they might happen, would be
a good thing to understand," said paper co-author Jamie Farrell,
another geophysicist at the university. "No one's ever witnessed one of
these really large volcanic eruptions. We kind of scale smaller
eruptions up to this size and say, 'This is probably how it happens,'
but we really don’t know that for sure.”
