An Underwater Volcano Off The Oregon Coast Sheds Light On Eruptions
6:14 minutes
This article is part of The State of Science, a series featuring science stories from public radio stations across the United States. This story, by Jes Burns, was originally published by Oregon Public Broadcasting.
A thick blue-white haze envelops the Research Vessel Thompson as it floats 250 miles off the Oregon coast.
Akel Kevis-Stirling’s orange life vest and blue hardhat are vivid pops of color in the fog.
“You guys ready to go?” he calls into his radio.
The person on the other end crackles an affirmative.
“Copy that,” he says and looks up across the rear deck of the research ship. “Alright, straps!”
The crew of the ROV Jason jumps into action, removing the straps that secure the cube-shaped submarine to the deck. The remotely-operated sub, with a base the size of a queen mattress, is loaded with scientific instruments it will carry down to the seafloor.
Kevis-Stirling gets final permission from the Thompson’s bridge for the launch.
“Ok, here we go. Jason coming up and over the side,” he calls. “Take it away Tito!”
The crane operator, Tito Callasius, lifts the submarine and swings it over the side of the ship into the water. A plume of fine bubbles rises through the waves as Jason starts its mile-long descent to the Axial Seamount, a deep-sea volcano that’s erupted three times in the past 25 years.
The scientific instruments on the sub—called bottom pressure recorders—will help reveal the inner workings of the Axial Seamount. And they could help us understand volcanic risk closer to home.
“As magma rises up underneath and accumulates under the surface, the whole volcano inflates like a balloon… pressure builds up,” says Bill Chadwick, the Oregon State University volcanologist who’s leading the cruise that took researchers out to sea for two weeks last summer. “Eventually that magma opens up a crack, finds a way out, erupts lava on the seafloor. [Then] the whole volcano quickly subsides back down.”
It’s a little counterintuitive, but the more the volcano seafloor rises, the less water it has on top of it. And the less water there is pressing down, the lower the water pressure readings on the ocean floor.
“As inflation is happening in the volcano, we will see a corresponding decrease in pressure in these instruments on the surface [of the volcano],” says Scott Nooner, a professor of geophysics at University of North Carolina Wilmington who has been making research trips out to Axial for 20 years.
The bottom pressure recorders use this change in water pressure to reveal how much the volcano has grown.
Chadwick says the surface of Axial will rise 8-10 feet as it builds towards eruption.
“That’s a lot of motion,” he says.
By collecting data year after year, the researchers, whose work and expedition were funded by the National Science Foundation, can track changes in the volcano as it inflates with magma to a literal breaking point.
Chadwick’s overall goal is to better understand how Axial and other volcanoes work, but the frequent eruptions of this deep-sea volcano sparked his interest in another, more practical, goal.
“By seeing that pattern a few times now, we can try to anticipate when the next eruption’s going to be,” he says.
Volcanic risk
Volcanologists can often forecast the eruption of volcanoes a few days in advance, but predicting eruptions on a longer timescale is much more difficult.
“A big component of our research is trying to understand what triggers eruptions,” Nooner says. “And then hopefully, we can learn enough about these systems [that] we can then start to look at other systems that might pose more of a hazard for people.”
Nooner and Chadwick forecast the 2015 Axial eruption about seven months in advance.
“This was the first accurate volcanic eruption forecast on the planet based off ground deformation data alone,” says Haley Cabaniss, an assistant professor of geology at the College of Charleston, who’s working with the science team on the Thompson. Cabaniss was an assistant professor at Eastern Kentucky University at the time of the Axial research cruise.
Half the people in the Pacific Northwest live within about 60 miles of an active volcano. Mount Hood, Rainier, Three Sisters, St. Helens and Mount Shasta are all characterized as very high-risk volcanoes by the U.S. Geological Survey. But only one—Mount St. Helens — has erupted in our lifetimes.
The Axial seamount — with its three recent eruptions in 1998, 2011 and 2015 — has been more active than any volcano in the contiguous United States.
In addition, Axial is the best monitored deep-sea volcano in the world because of a fiber-optic cable sending real-time data from the caldera directly back to the Oregon coast.
“[Observing] multiple cycles of eruption … is really powerful when you’re trying to understand what’s going to happen in the future,” Cabaniss says.
And any additional insight these researchers could learn from Axial to better understand and predict volcanic activity could ultimately help save lives.
“This volcano, when it erupts, it doesn’t pose any great risk for people. But what we can learn from this system, and hopefully apply to volcanoes on land that do have the potential to cause lots of harm and to kill people is really valuable,” Cabiniss says.
Now they’re trying to figure out what Axial will do next.
The anatomy of Axial
Axial is a shield volcano that sits on the Juan de Fuca Ridge (west of the Cascadia subduction zone), where two tectonic plates are spreading apart.
“There’s volcanic activity all up and down the ridge, and that’s where new seafloor is created by eruptions,” OSU’s Chadwick says.
But Axial doesn’t seem to blow its top when it erupts like Mount St. Helens. Instead, the magma below often causes it to crack open on its slopes and ooze lava—kind of like Kilauea does on the Big Island of Hawaii.
“We’re trying to understand how the magma moves around, where it comes from, how it’s distributed… how the magma moves leading up to an eruption, during an eruption. What happens right after an eruption?” says Nooner. “These are things that are not really that well understood that volcanoes in general.”
Another thing Axial has in common with the Hawaiian volcanoes is that it sits atop a hot spot—essentially a magma pipeline from deep in the earth. This additional source of magma is a reason Axial is so active.
“You know in general, I think we learn the most about how volcanoes work by studying them in the act of doing something,” Chadwick says.
On the ocean floor, on top of a volcano
To make their predictions, the researchers aboard the RV Thompson need to understand what’s happening inside the volcano. This means slowly traveling around Axial’s caldera with their submarine, collecting and deploying their sensors.
It takes three people—a pilot, engineer and navigator—to control the ROV Jason up on deck. They work in a shipping container that’s been converted into a command center. It operates around the clock, whenever Jason is in the water.
Inside the command center—called a “van”—it’s dark and serene. It hypnotically shutters and creaks as swells pass under the ship. A bank of screens covering one wall shows seemingly endless miles of obsidian-encrusted lava flows Jason passes on the ocean floor—and the occasional curious spider crab or rat-tail fish.
“Every now and again there’s just something on the screen that makes you go, ‘Wow,’” says Oregon State University geologist Jeff Beeson.
Beeson is directing the deployments of the pressure recorders—yellow cylinders about 5 inches wide and a little longer than your forearm. He tells his colleague to pilot Jason to a small, round concrete platform placed on the volcano by the team on a previous research cruise.
The pilot uses a specialized joystick to manipulate one of Jason’s titanium claw-arms and positions the instrument on the platform. But he’s a little off.
“You’re close to the edge,” Beeson observes as the claw releases its grip.
The pilot deftly adjusts the canister and goes to secure a second instrument on the sub. But this one hangs up on the storage basket. As the arm pulls it free, the recorder’s protective mesh and the base slide off the main body.
“Oh no! What have you done,” Beeson laments. “My baby!”
A moment later, Nooner enters the van and sees the state of the instrument on the screen.
“Who put that together?” he says good-naturedly.
“Don’t ask,” Beeson replies, and then turns to the rest of the crew working in the van. “He’s making fun of me because I put it together two years ago.”
After a few minutes of troubleshooting, they manage to secure both sections of the pressure recorder to the sub for the long trip to the surface.
Accurate and secure placement of the instruments is important because the recorder will spend its next two years in the dark and cold of the deep ocean collecting data.
“It’s a humble looking instrument but very powerful in what it can record for how long and the sensitivity of it,” Beeson says.
The information it collects will provide more clues for the research team as they attempt to forecast the next eruption of the Axial Seamount.
Forecasting pitfalls
Making long-term forecasts of volcanic activity is notoriously difficult and Chadwick’s current method of tracking magma inflation—deformation of the seafloor—may or may not be repeatable in the long term.
Given what they know about the current temperament of Axial, the time window for an eruption is still several years away—maybe.
During the current inflation cycle, the magma under Axial increased rapidly in the years after the 2015 eruption. Seeing this, Chadwick forecast Axial would erupt between 2020 and 2024.
But beginning around 2019, the inflation rate dropped off—like the earth was running out of breath.
As of 2022, the volcano was inflated to about 90% of where it was when it erupted in 2015, but it’s growing very slowly.
“I’ve had multiple time windows and had to change them. So, you know there’s an asterisk after each one: Subject to change,” Chadwick says.
But what the Axial Seamount provides is a natural laboratory—the perfect place to practice this kind of forecasting.
“At a real dangerous volcano, you don’t want to be issuing any predictions that you’re not sure are going to be true, because people might have to evacuate. You know there could be economic costs and freaking people out,” Chadwick says.
The negative impact of false alarms (and the lack of effective messaging about volcanic risk) has reared its head in the Pacific Northwest in the past.
In 1975, Mt. Baker in Washington started to show signs of volcanic life. The U.S. Geological Survey recommended closures in the area because of risk of lahar (volcanic mud or debris flows) or even eruptive activity. Because of the warnings, people stayed away from the mountain and businesses in the surrounding communities felt the hit.
“Then because nothing happened, they were mad,” says Heather Wright, volcanologist with the USGS Cascades Volcano Observatory and the Volcano Disaster Assistance Program. Wright is not affiliated with the work at Axial Seamount.
Wright says that negative community impact was on scientists’ minds a few years later when Mount St. Helens became more active. It added to the challenge of preparing nearby communities for the eruption.
“I don’t think people sat down and said, ‘Okay, let’s not say that. Let’s only say this,’”she says. “I think it was more like we don’t want to scare people and create another disaster all on its own, like an economic disaster.”
Scientists face the challenge of walking a fine line when it comes to communicating risk: Too passive and people get hurt, too alarmist and the public loses trust.
“You can have the best forecast possible, and if people decide they don’t want to listen to you, then it doesn’t matter,” Wright says
Out at the Axial Seamount, none of this is a problem.
“Here there’s just a bunch of tube worms and octopuses on the seafloor. They don’t care,” Chadwick says.
Increasing complexity
Because of the limitations of trying to consistently predict volcanic eruptions based on the inflation/deflation eruption cycle, Chadwick wants to add other telling variables to his forecasting mix.
“Most of what I started with was … pattern recognition, right? There’s not much science to it,” he says, “It’s like, ‘Let’s see how repeatable this is.’ And if it is, then hey, that could be useful.”
But there’s interest in the world of volcano science to go beyond pattern recognition.
“Trying to make forecasting more physics based … You know, we can estimate the pressure, and we know the strength of the rock. How much can we anticipate when it’s going to fail and lead to an eruption?” he says.
Chadwick is interested in looking at a variable pointed out by researchers working at other volcanoes around the globe: How earthquake activity (seismicity) relates to inflation of the seafloor. And can that relationship be used to improve forecasts?
He’s noticed at Axial that after an eruption, the volcano starts to inflate. There’s a lot of movement of the seafloor, but no earthquake activity to speak of.
“Then as you get closer to the next eruption, the number of earthquakes skyrockets. How are those things related?” Chadwick says.
In addition, at some other volcanoes, there’s a moment near the point of eruption where the relationship between deformation and seismicity changes.
Chadwick plotted current inflation data against seismicity at Axial and he saw a similar relationship. And now he’s looking for the inflection point—the moment when conditions change..
“We’re going to be seeing if, as we approach to the next eruption, we can see this change in this relationship. That would really tell us: this is an indicator that we’re getting near the eruption.’”
Using these more complex methods could help improve forecasting accuracy. But the complexity and scale of the forces at play in volcanic systems make this work tricky at best.
“If you think you know what’s going on, nature will usually make you humble, or humbler, by doing something you didn’t expect,” Chadwick says.
Yet with each passing trip to the Pacific Northwest’s most active volcano, the scientists get closer than they’ve ever been before to understanding what makes Axial and other volcanoes tick.
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Jes Burns
Jes Burns is a science reporter with Oregon Public Broadcasting in Portland, Oregon.
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