Scientists predict the Pacific Northwest’s most active volcano, 300 miles offshore, will erupt this year

An undersea volcano off Oregon’s coast will likely erupt in 2025, scientists say.

Known as Axial Seamount, it’s the most active volcano in the Pacific Northwest – though one most people haven’t heard of because it lies about 300 miles offshore and just under a mile beneath the ocean waves.

Its eruption won’t trigger a tsunami or a massive land-based earthquake because of its depth and its distance from the region’s megathrust Cascadia fault. But scientists can use the lessons learned from forecasting its eruption and watching it unfold to monitor other more hazardous and unpredictable volcanoes.

“If we’re successful at forecasting eruptions at Axial then we can apply what we learn to other volcanoes around the world that are more dangerous to people and are in more complex settings,” said William Chadwick, a professor of geology at Oregon State University who is leading the research at Axial.

Months of advance notice about a volcano erupting are rare – typically, scientists can reliably predict an eruption only a few days or even hours in advance. But Axial Seamount, located where two tectonic plates – the Juan de Fuca and the Pacific plates – are moving apart, is one of the most highly studied volcanoes on Earth.

Axial was first detected by satellites in the late 1970s. Scientists have measured the deformation of its surface since the late 1990s, including prior to three eruptions, in 1998, 2011 and 2015. The frequent volcanic activity is due to its location over a hotspot with an overabundant magma supply, Chadwick said.

Unlike the Pacific Northwest’s steep-sloped Cascade volcanoes such as Mount St. Helens or Mount Hood that tend to explode when they erupt, Axial Seamount’s magma forces its way out as fluid lava that flows down broad, gentle slopes much like at volcanoes in Hawaii or Iceland. From the surrounding seafloor to its summit, Axial measures over 3,300 feet.

The seafloor near the volcano rises slowly in between eruptions. After the volcano pours lava onto the seafloor, it quickly goes back down.

“Axial’s summit inflates like a balloon as magma is supplied from below and stored in the reservoir beneath the volcano summit,” Chadwick said. “The balloon keeps getting bigger and bigger. And at some point, the pressure becomes too great and the magma forces open a crack, flowing to the surface. When that happens, the seafloor subsides as the ‘balloon’ deflates.”

Axial Seamount’s three previously observed eruptions occurred each time the seafloor rose to a certain level. That’s why Chadwick’s team is using the measurements of inflation to predict the next time it will blow.

BEST-MONITORED UNDERSEA VOLCANO

This fall, Chadwick’s team noticed the ground around the seamount had risen to nearly the same level as it had before its last eruption in 2015, leading him to forecast the next eruption for sometime this year.

The team uses precise pressure sensors to detect whether the sea floor is moving up or down and how much. Bottom pressure battery-powered recorders had been used at the volcano since 1997. But since 2014, the pressure sensors along with myriad other scientific instruments have been attached to a fiberoptic cable that runs in the ocean from Pacific City to Axial Seamount. The cable – part of an underwater observatory – allows Chadwick to stream data from the sensors directly into his computer in real time.

“I can look at my laptop and see data that was collected 10 minutes ago at Axial,” Chadwick said. “It makes it the best monitored submarine volcano in the world.”

There’s a catch.

On one hand, Axial Seamount is the perfect volcano to study because it’s “well-behaved,” with a relatively simple structure and thin crust, Chadwick said, meaning its ground slowly rises and drops in a regular sawtooth pattern. Other volcanoes with more complex structures have thicker crusts or nearby faults and don’t follow the same pattern each time, making their eruptions much harder to predict, he said.

But Axial Seamount’s pattern seems to have altered somewhat after the 2015 eruption, leading Chadwick to make several previous forecasts that turned out to be incorrect.

The rate of inflation, which had been relatively high and linear before the 2011 and 2015 eruptions, steadily decreased after 2015. In the summer of 2023, the ground stopped rising almost completely, he said. But then it started to increase again. By summer and fall of 2024, it was very high again and the number of earthquakes had increased significantly as well.

“We’re at the 2015 inflation threshold, we’re almost fully reinflated and we’re inflating again and there’s lots of earthquakes,” Chadwick said. “So it’s a good time to try to make another forecast window.”

If the forecast proves accurate, scientists can apply the science to other volcanoes, said Michael Poland, a geophysicist with the U.S. Geological Survey.

That’s key because fewer than half of the world’s above-water volcanoes and a tiny number of below-water ones have real-time monitoring systems, he said. And the vast amount of data needed to make predictions about seismic and ground inflation patterns has only been available to scientists in recent years, making Axial – where monitoring has been ongoing for three decades – somewhat of a “unicorn,” Poland said.

“That we as a society are able to forecast eruptions of a volcano that’s offshore and under an awful lot of water, that’s amazing,” he said. “If you can develop a model for how this works at Axial, it gives us a starting point that we can apply elsewhere and, with a few tweaks, we can begin working on forecasts of other volcanoes.”

DIFFERENT THAN TONGA

To Chadwick, the forecast is an experiment and one he’s free to make because it lacks negative consequences – he’s studying a deep underwater volcano that poses no threat to humans.

“People’s lives aren’t in the equation,” he said. “On land, you can’t do this forecasting without worrying about false alarms and freaking people out and having economic impacts. You don’t want to evacuate towns and all that without knowing for sure that you need to.”

Axial Seamount’s eruption won’t cause any damage because it’s so deep, Chadwick said. That’s unlike the Tonga underwater seamount that erupted in 2022 and led to a colossal explosion and tsunami – including surges in the Pacific Northwest.

The difference? The Tonga seamount’s crater rim lies a little above sea level so the volcano exploded in shallow water, which means seawater couldn’t dampen the explosion and instantly turned into steam, further driving the explosion, Chadwick said.

Axial’s eruption also won’t trigger “the Big One” – the much feared Cascadia earthquake – because it’s located on the ridge of two different tectonic plates and is too far away from the Cascadia Subduction Zone, a 600-mile fault that runs from California to British Columbia about 70 to 100 miles off the Pacific coast shoreline.

“If you were sitting in a boat over Axial when it erupted, you probably would never know it, unless you put a hydrophone in the water and then you might hear some sounds coming from the deep,” Chadwick said. A hydrophone is an instrument that detects sound waves under water.

NATURAL LABORATORY

Chadwick fell in love with volcanoes while in college in Colorado. When Mount St. Helens erupted in 1980, he volunteered to work with the U.S. Geological Survey.

“Before I knew it, I was flying in a helicopter into the crater. The first dome-building eruption happened while I was there,” he said. “And I thought, this is the most exciting thing I can imagine.”

After college he worked at Mount St. Helens for the USGS, returned to graduate school, then turned to studying hydrothermal vents and underwater volcanoes off the Oregon coast. His research has taken him on nearly a dozen dives in manned submersibles. He likens it to being a detective, collecting evidence about the volcano, its eruptions and what triggers them.

Nowadays, he mostly observes the seafloor from a ship’s control room, as he did in June when the research ship R/V Atlantis hovered over the Axial Seamount and a robotic vehicle went down on a cable and sent live data and video up to the deck. The research is funded by the National Science Foundation.

Chadwick’s team watched as the submersible made its way inside the underwater caldera, along a seafloor covered in solid lava flows from past eruptions. They observed hydrothermal vents – underwater hot springs – teeming with bright red-gilled white tube worms and spectacular mineral chimneys billowing what looked like black smoke but was actually hot water laden with metal particles.

Underwater volcanoes are the next frontier for science, Chadwick said, because they’re not well understood or studied given their inaccessible locations. But, three quarters of the Earth’s volcanic activity happens in the oceans, he said.

In the near future, artificial intelligence and machine learning may prove immensely helpful in analyzing vast volumes of data collected as part of volcanic monitoring – including both to discern patterns that humans can’t see and to design models based on the physics of magma chambers to forecast future eruptions, Chadwick and Poland said. As that technology develops, scientists at Axial will continue to collect the data that’s needed.

“The Axial Seamount turns out to be a great natural laboratory for studying how submarine eruptions work and how volcanoes work in general,” Chadwick said. “And it might be able to teach us some useful things about how to forecast eruptions… and to lift the veil about what’s happening in the oceans.”