Seismologists from the University of Utah have discovered a reservoir of magma so big; it could fill the Grand Canyon 11.2 times.
It’s located 12 to 28 miles beneath the Yellowstone supervolcano and is 4.4 times larger than the shallower magma chamber researchers have known about for years.
“For the first time, we have imaged the continuous volcanic plumbing system under Yellowstone,” says first author Hsin-Hua Huang, also a postdoctoral researcher in geology and geophysics. “That includes the upper crustal magma chamber we have seen previously plus a lower crustal magma reservoir that has never been imaged before and that connects the upper chamber to the Yellowstone hotspot plume below.”
Most of us picture a vast reservoir of hot lava. That’s not the case. The rock is hot, but it’s “mostly solid and spongelike, with pockets of molten rock within it,” according to the press release.
In fact, Huang says their new study shows the upper magma chamber averages only 9% molten rock. That is inline with estimates of 5-15%. The lower magma reservoir has just 2% molten rock.
So, should we expect something like this soon?
Not so fast, says researchers. They were quick to emphasize the discovery does not mean Yellowstone is closer to erupting than before. All they did was get a more detailed look of the magma chamber.
“The actual hazard is the same, but now we have a much better understanding of the complete crustal magma system,” says study co-author Robert B. Smith,
“The magma chamber and reservoir are not getting any bigger than they have been, it’s just that we can see them better now using new techniques,” said Jamie Farrell, co-author of the study.
The University of Utah researchers used seismic imaging to scan deep below Yellowstone. Imagine a medical CT scan on the supervolcano, but using earthquake waves instead of X-rays. The earthquake waves can tell researchers the density of the rock. They travel slower through hot and molten rock, and faster through cold rock.
Yellowstone erupted three times in the past – 2 million years ago, 1.2 million years ago and 640,000 years ago.
Each of the three eruptions produced vast amounts of ash that covered North America.
The annual chance of Yellowstone eruption is 1 in 700,000 according to Smith.
The Yellowstone Caldera experiences 1,000-2,000 measurable earthquakes per year. Most of these measure a magnitude of 3 or lower.