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Yellowstone's underground plumbing is becoming more clear.

Guided by more and better technologies, researchers are developing an ever-increasing understanding of the volcanic system beneath the world's first national park.

And University of Utah seismologists have just discovered another massive reservoir of lava and rock 12 to 28 miles below Yellowstone and nearly 4½ times larger than a previously identified magma chamber closer to the surface.

It's so big, in fact, that the researchers used another natural wonder to describe the sheer volume of the partially molten rock.

"The deeper magma reservoir would fill the 1,000-cubic-mile Grand Canyon 11.2 times, while the previously known magma chamber would fill the Grand Canyon 2.5 times," said Jamie Farrell, a co-author of the study.

The reservoir is roughly 12 to 28-miles deep and and measures 30 to 44 miles across. It is connected to Yellowstone's hotspot plume, which some researchers believe originates 1,800 miles into the planet at the Earth's core.

A smaller magma chamber identified several years ago — about three to nine miles deep and 2,500-cubic miles big — sits below the Yellowstone caldera. Last year, researchers published a study showing the reservoir was 2½ times bigger than previously thought.

The latest research on Yellowstone's giant subterranean volcano was published in the journal Science Thursday.

University of Utah seismologists Fan-Chi Lin, Hsin-Hua Huang, Robert Smith and Farrell worked with Brandon Schmandt at the University of New Mexico and Victor Tsai at the California Institute of Technology to map the newly-discovered magma chamber.

Scientists had long expected a deeper reservoir existed due to the high volume of carbon dioxide released by Yellowstone's surface features. Carbon dioxide is created by molten and partly molten rock.

Researchers used data gathered from numerous earthquakes in the Greater Yellowstone area — Idaho, Wyoming and Montana — and around the world to generate seismic imaging of the park's underbelly.

"For the first time, we have imaged the continuous volcanic plumbing system under Yellowstone," said Huang, first author of the study and a postdoctoral researcher in geology and geophysics at the University of Utah.

Huang used U. seismograph recordings of earthquakes in Utah, Idaho, the Teton Mountains and in the national park itself. Researchers then combined those reports with data from earthquake information gathered by National Science Foundation seismometers.

Seismic imaging, similar to a CT scan, but using earthquake waves instead of X-rays, was then used to identify the various components of the magma system. Earthquake waves, according to the researchers, travel faster through cold rock and slower through hot and molten rock.

The Yellowstone area averages 2,000 to 3,000 earthquakes each year, providing a plethora of waves to map the shallow lands below the park. Larger waves from around the planet were required to graph the deeper areas of the magma chambers.

"The best wave forms came from Alaska," said Smith. "Waves from around the globe, like the Antipodes Islands on the other side of the Earth, send waves straight through to help us see what was happening deeper."

He expects scientists around the world will utilize the technology to study other volcanic systems.

"We never had the instruments [before] to provide the first continuous image of the magma system," Smith said.

Smith, a research and emeritus professor of geology and geophysics at the U., started working in Yellowstone right out of high school in 1956. He has long been regarded as the leading authority on earthquakes and volcanism.

The researchers emphasized their study only reveals something they had long suspected and is not the result of Yellowstone's "supervolcano" preparing to erupt.

"The magma chamber and reservoir are not getting any bigger than they have been," Farrell said. "It's just that we can see them better now using new techniques."

Lin said the ability to map the system might lead to better planning should the volcano become more active.

"It gives us a better understanding of the Yellowstone magmatic system," he said. "We can now use these new models to better estimate the potential seismic and volcanic hazards."

Researchers believe massive eruptions from Yellowstone occurred 2.1 million, 1.3 million and 640,000 years ago.

The most recent eruptions, Smith said, happened about 70,000 years ago.

"There is a .00014 percent chance the volcano will erupt each year," Smith said. "Some would say that is a zero. On the other hand, there is probably a big earthquake every 800 years."

Twitter: @BrettPrettyman