Mauna Loa, Earth’s largest active volcano, abruptly woken on November 27After a nearly 40-year-long nap. The volcano shot fountains of lava as high as 50 meters into the air, while rivers of molten rock streamed down the volcano’s flanks toward Saddle Road, the main highway on Hawaii’s Big Island.
Mauna Loa can be seen shoulder to shoulder alongside four other volcanoes, such as Kilauea can be explosive (SN: 7/16/18() Mauna Kea quietly grumbles (SN: 5/14/20). In recent years, Kilauea’s pyrotechnics have made headlines, while Mauna loa has been quiet. But the sleeping giant hasn’t been so quiet in the past, says Ingrid Johanson, a geophysicist at the U.S. Geological Survey’s Hawaiian Volcano Observatory in Hilo.
She says that Mauna Loa would wake up approximately every seven years in the past. This last stretch between eruptions “is quite a big gap.”
Science News talked with Johanson about how Mauna Loa tends to wake up, what’s in the path of the lava and what sort of neighbors Kilauea and Mauna Loa are.
Did you see warning signs that Mauna Loa was about erupting?
“It depends on what you mean by warning,” Johanson says. “In a manner of speaking, we’ve known that Mauna Loa was showing signs of unrest since 2015.” At that time, she says, there was an uptick in the rate of local earthquakes, as well as in GPS observations of land deformation — a bulging upward of the land surface that indicates magma is on the move below ground.
Those signs tapered off a bit and then increased again over the last six months, suggesting “that the situation was evolving,” Johanson says. But when the volcano would actually erupt wasn’t possible to determine. “Fundamentally, we had about an hour and a half of warning,” she says. Researchers noticed the sudden swarming of earthquakes that indicated an imminent eruption.
That short notice is “true to form” for Mauna Loa, she adds. Its “other eruptions have evolved very quickly in the same way.”
What is the difference between the monitoring of Mauna Loa and before the eruption of 1984?
“One of the big differences between 1984 and now is the technology,” Johanson says.
“We can see more earthquakes [and]You can detect more frequencies in seismic waves. And we have GPS and electronic tiltmeters to measure deformation continuously.” That technology allowed scientists to detect not only that there was land deformation recently, but also how it was changing over time, giving just a bit of extra warning time.
That wasn’t possible 40 years ago. Back then, researchers measured deformation by hand, hiking up to the volcano’s summit every few weeks or so. “There was a technique called EDM, for electronic distance measuring, which was essentially shining a laser into a reflector, so you could get very precise distance measurements,” Johanson says. Subtle shifts in the reflector’s location, installed on the volcano, helped reveal the deformation.
Is the current eruption a danger to people?
“It’s a little early to tell — it’s not yet clear how much volume we can expect out of this eruption,” Johanson says. “I don’t think it’s a given that this will be a more momentous eruption than past ones, but there is a sense of maybe coming back to business as usual for the volcano.”
The good news is that the lava flows don’t currently pose a threat to communities on the Big Island. However, Saddle Road connects the island’s eastern and western sides, Johanson notes. “If the lava were to cross the highway, it would really impact the island.”
But the eruption has interrupted data collection for one of climate science’s most iconic charts: the Keeling Curve, a nearly unbroken 60-year record of atmospheric carbon dioxide that shows a steady rise in levels of the gas.
The Mauna Loa Observatory collects carbon dioxide data. The observatory was cut off by the eruptionNovember 28, 2008. The power had not been restored as of November 30. Access to the site was also blocked by lava flows. For now, it’s unclear if the interruption will have a lasting impact on data collection.
Kilauea has been erupting almost continuously for many decades. How is Kilauea and Mauna Loa related?
They are two separate volcanoes with geochemically distinct lavas, suggesting their plumbing systems — the networks of tunnels and channels through which magma moves — are separate. Johanson believes that the plumbing separation is likely to occur below the crust or in the mantle. But ultimately, the volcanoes tap directly into the. same mantle hot spot (SN: 1/6/22).
She says that Kilauea is a neighbor, and they communicate through underground pressure changes and stress. Subtle pressure changes can affect one volcano’s plumbing. This could alter the ability of one volcano to expand and make way for more magma. “They do kind of elbow each other a little bit.”
