Apart from the hot springs and bubbling geysers, Yellowstone National Park is also home to a massive volcanic hot spot. Beneath Yellowstone’s super-volcano, which is responsible for three gigantic eruptions in the last 2 million years, a newly-found reservoir of hot melted rock was mapped for the first time.
Despite not having erupted in the last 640,000 years, the Yellowstone National Park’s super-volcano is one of the planet’s largest active volcanoes.
With a jaw-dropping 11,000 cubic-mile volume, this newly discovered magma reservoir lies 12 to 28 miles underneath the surface. Hsin-Hua Huang, Utah University seismologist and study author, explains that the team’s research unveiled a larger and deeper magma reservoir whose discovery only begins to connect the dots as to how Yellowstone Park is connected to deep heat plumes stemming from the Earth’s mantle.
Missing Link Between Magma Chambers
Scientists were already aware of the plume transporting molten rock from 60 kilometres underneath the Earth’s surface. They had also imaged the magma reservoir located 10 kilometres underneath the surface (the shallow chamber). What they hadn’t been aware of was this massive reservoir, which is 4.5 times larger than the shallow chamber previously mentioned.
This amount of hot rock would be enough to completely fill the Grand Canyon 11 times.
Despite not having erupted for over 640,000 years, geologists were convinced that massive amounts of lava had to exist underneath Yellowstone Park’s volcano. The only issue was finding this magma. These large amounts of energy escape as carbon dioxide gas and reach the surface through geothermal features.
Scientists reasoned that Yellowstone National Park was producing significantly larger carbon dioxide quantities than its previously imaged magma chamber could have accounted for. Another nagging question was how this magma chamber connected to the Earth’s mantle.
Peter Cervelli, geophysicist with the US Geological Survey’s Yellowstone Volcano Observatory, explains that Huang and his team’s discovery is precisely the missing link which scientists had long anticipated but never found. The internal plumbing system has finally been mapped so that geophysicists can now understand precisely how the mantle plume is connected to the shallow magma chamber.
Intricate Transport System Between Magma Chambers
This newly discovered reservoir is mostly comprised of solid rock. Only 2 percent of its 11,200 cubic-mile volume is magma, which is enclosed in the solid rock’s pores. As compared to this reservoir, of the shallow chamber’s volume, 10% is magma.
What geologists realized was that, from the top of the mantle’s plume, magma is transported 12 miles through the intricate net of vertical cracks (dikes) until finally reaching the first reservoir. A similar system of dikes is most likely involved in transporting the magma towards the shallow chamber, although such a system is yet to be proven.
“Now we really have a complete image of the Yellowstone plumbing system,” Jamie Farrell, study co-author, said.
Discovering the Massive Reservoir
A method called “seismic tomography” was used to accurately map the magma reservoir.
Huang and his team employed seismometers in their search for the massive magma reservoir. They were attempting to detect seismic waves stemming from earthquakes and analysing the time variations required for them to register on distinct instruments.
Different density materials conduct seismic waves differently. Hotter, molten material, for instance, conducts seismic waves slower, so that a delay in their detection would appear. Pulling data from two different networks and comparing the results, researchers were able to construct an accurate map of the deeper magma reservoir.
The mathematical method used by the research team to map out this magma reservoir would incorporate seismic data the world over with that of local Yellowstone earthquakes, merging the travel time information in order to connect “amazing three-dimensional images of this entire connected system.”
The technique itself, Huang mentions, wasn’t new. However, no one had previously applied it to Yellowstone National park’s volcano.
Geologists can now use this technique for additional modelling projects, especially in the case of hard-to-reach super-volcanoes hidden underneath the oceans. Apart from having explained the clear discrepancy between the carbon dioxide amounts given off by Yellowstone’s geothermal spots and its shallow magma reservoir, Huang’s research also sheds light on how super-volcanoes are fed.
In the future, geologists may apply the same seismic tomography methods in their attempts of estimating a volcano’s current state.