A U.S. Geological Survey geochemist has confirmed that the ongoing eruption at Kilauea Volcano gets its supply of lava from two small sources beneath the earth’s crust, not one large one.
The research led by Aaron Pietruszka, who studies Kilauea lava samples in a lab in Denver and wrote his doctoral thesis on Kilauea as a University of Hawaii graduate student, offers a better understanding of how lava from 37 miles below Hawaii island feeds one of the planet’s most active volcanoes.
Pietruszka’s study also offers new hope toward being able to one day predict when an eruption will occur — and when it will end.
Kilauea has been continuously erupting since Jan. 3, 1983.
"The more we learn about what the volcano looks like, the better job we can do in understanding the future," said Michael Poland, a U.S. Geological Survey geophysicist who consulted on a draft of Pietruszka’s study and conducted his own research at Kilauea before moving on to Washington’s Cascades Volcano Observatory last month. "One day we might be able to forecast when an eruption starts or stops. That’s the ultimate goal."
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DEEP FROM DOWN UNDER
New evidence debunks a theory that lava from Kilauea Volcano flowed up from one giant pool beneath the surface of the earth. Instead, two smaller pools feed the eruption that has gone on continuously since Jan. 3, 1983, leading to hope that scientists one day can predict when the current eruption will end. If lava no longer comes into the magma chambers, there would only be enough magma left to erupt for another five years.
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Volcano researchers had long believed that Kilauea must be fed from an enormous underground "magma chamber" that stored and mixed magma from far below before it spewed out onto the surface.
"People thought there was one enormous magma chamber until the late 1990s and early 2000s, when geophysicists started thinking there were two," Pietruszka said. "But they had no real idea how big they were. I confirmed there have to be two based on the chemistry — and they’re not large. They’re actually quite small. They’re poorly connected, and there can’t be a single magma chamber."
Pietruszka studied Kilauea lava samples from various eruptions over the years and found distinctly different isotope ratios, much like human fingerprints, that proved different eruptions originated from different sources.
One magma chamber lies southeast of Halemaumau fire pit near the southern rim of Kilauea Caldera at a depth of 1 to 2 miles. The other is just a mile deep, below the eastern rim of Halemaumau.
Pietruszka’s study brings together two distinct volcano disciplines: geophysics and geochemistry.
"For quite a while we knew there was a magma storage area," said Poland, a geophysicist. "But geophysicists saw separated storage areas. We knew there was a smaller one, 1 mile below Halemaumau and a deeper one. Geochemists saw no evidence. We were clearly not on the same page. Now we’ve gotten over the first hurdle in agreeing there are these multiple reservoirs, multiple magma chambers. Now we have the same sort of agreement over what the subsurface looks like."
Combined, Pietruszka believes the two magma chambers can hold only 0.5 cubic kilometer — or 0.12 cubic mile — of magma. That volume is comparable to 4,800 Empire State Buildings or Nimitz-class aircraft carriers.
The chambers move magma efficiently to the surface.
"There is not enough magma storage there to supply the eruption," said Pietruszka. "The earth’s mantle is rising toward the surface and melting efficiently and quickly and constantly. There must always be new magma to replenish what’s erupted."
Based on Pietruszka’s estimates, the capacity of the magma chambers means there would be a limited supply if magma stops flowing from below.
"It’s encouraging that the amount of magma down there is relatively small," Pietruszka said. "If the supply ceased today, without new replenishment, the most an eruption could last would be five years."
