Undersea volcano off West Coast could erupt soon but should you prepare for a disaster?
The Axial Seamount sits on the bottom of the Pacific Ocean, reaching about 3,500 feet above the surrounding seafloor.
Watch: Expedition to Axial Seamount shows lava flows from 2015 undersea eruption
A video shared by Oregon State University Professor Bill Chadwick shows new lava flows from the 2015 eruption of the Axial Seamount on the floor of the Pacific Ocean.
One of the most active volcanoes in the world sits just a few hundred miles off the U.S. West Coast, and some scientists believe it’s only a matter of time before it erupts again – maybe even before the end of 2025.
But unlike mammoth mountains like Washington state’s Mount St. Helens or Oregon’s Mount Hood and Mount Jefferson, this one doesn’t tower thousands of feet into the air.
Instead, the Axial Seamount sits on the bottom of the Pacific Ocean, reaching about 3,500 feet above the surrounding seafloor.
"So, it's relatively small, but it's the biggest thing around it," said Bill Chadwick.
Oregon State University Professor Bill Chadwick points to monitors on the most recent expedition to the Axial Seamount off the U.S. West Coast.
(Dave Caress, MBARI / FOX Weather)
Chadwick is a research professor with Oregon State University's Hatfield Marine Science Center.
He said that the region sits atop a plate boundary where the Earth's tectonic plates are spreading apart, and while volcanic activity occurs up and down the boundary, it doesn't happen often.
Except at Axial, Chadwick said.
"At Axial, (eruptions) are more frequent because, in addition to being on the plate boundary, it's also over a hotspot, which is like what's under Hawaii or Iceland," he continued.
Watch: Lava shoots from fissure during eruption of Hawaii's Kilauea volcano
The USGS provided video from the first helicopter flight over the eruption of Hawaii's Kilauea volcano showing lava shooting from a massive fissure on Monday, June 3, 2024. (Video from June 2024)
Hawaii is home to the world's most active volcano – Kilauea – which has been actively erupting since December 2024. And in Iceland, a volcano has erupted numerous times since the end of 2023, forcing the evacuation of a town and even the popular travel destination Blue Lagoon.
A "hotspot," Chadwick explains, is a point source of extra magma supply in one place.
"We don't know why they form, but they're scattered around the world," he said. "So, Axial's on the spreading ridge, but it's also over a hotspot. That's why it has an extra magma supply. And that's why it's the most active volcanic site, you know, on the ridge and in the northeast Pacific."
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Axial Seamount is a shield volcano, which means it's shaped like a shield rather than a steep-sided cone volcano. Its caldera at the top is a few miles wide and long, and about 300 feet deep.
Unlike other volcanoes around the world that can go centuries between eruptions, this one can be measured in years. The most recent eruptions occurred in 1998, 2011 and 2015.
"The last three eruptions are the ones we know about, and they all started in the caldera and then went either north or south down the rift zones," Chadwick said. "And the eruptions can span quite a distance, like 30 to 50 kilometers (18.6-30 miles)."
Why do scientists think Axial Seamount could erupt soon?
This bathymetric map shows the shape and summit caldera (warm colors are shallow depths while cool colors are deeper) at the Axial Seamount.
(Susan Merle/Oregon State University / FOX Weather)
Under the summit of Axial Seamount sits a magma reservoir about a mile deep. Chadwick said magma is continuously being supplied to that reservoir, but it can't keep filling up forever.
"We're measuring the uplift of the seafloor," Chadwick said. "Pressure builds in that reservoir until it reaches some threshold, and then a crack opens up, and magma ascends through the crack. So, that will open a fissure in the caldera. But then the magma can intrude for miles and miles as that crack just keeps propagating with magma in it and erupting in different places along the fissures."
Which, again, Chadwick said, is very similar to volcanic eruptions in Hawaii or Iceland.
This image shows lava from a fissure that opened up during another volcanic eruption in Iceland on Wednesday, Nov. 20, 2024.
(@jvn.photo via Storyful / FOX Weather)
Take Iceland, for example. With the region facing numerous eruptions from a volcano since the end of 2023, dramatic photos and video show lava shooting from a long fissure that opened up.
That's what an eruption at the Axial Seamount looks like, except lava spreads across the ocean floor and doesn't shoot into the air.
The region is filled with equipment, including a long cable, that measures even the tiniest of movements and relays data back to scientists in real time.
Chadwick said that after the 2015 eruption, the area was inflating quickly at first and then became steady.
WHAT HAPPENS BEFORE A VOLCANO ERUPTS?
Watch: Lava shoots from fissure during eruption of Hawaii's Kilauea volcano
The USGS provided video from the first helicopter flight over the eruption of Hawaii's Kilauea volcano showing lava shooting from a massive fissure on Monday, June 3, 2024.
"We started extrapolating and trying to anticipate the time that it would take to get up to the previous inflation threshold," Chadwick said. "But the inflation rate kept slowing and slowing, and that kept pushing the window farther and farther ahead. So, our attempts to forecast the timing of this next eruption have not been very successful."
But there are two different parts to the forecasting. One part, Chadwick said, is just the question of whether or not it's going to erupt again when it reaches that previous inflation threshold or above it.
The other part is anticipating the timing of the possible next eruption.
"We're almost totally, fully reinflated, so there's sort of less ambiguity about timing," Chadwick said.
More than a year ago, Chadwick said the inflation rate and earthquake rate were low. But that has changed.
"In the fall of 2023, and especially in 2024, the rate of inflation slowly picked up again, and the number of earthquakes really increased," Chadwick said. "So, then it was like, ‘OK. Now it’s waking up. Now it's finally building up to the next eruption.'"
When do scientists think it could erupt again?
This image shows lava from the 2011 eruption at the Axial Seamount off the U.S. West Coast.
(Bill Chadwick/Oregon State University / FOX Weather)
It could be somewhat soon.
"We're currently saying that we think it's going to erupt by the end of the year, the end of 2025," Chadwick said. "It's still uncertain, I would say. We made that forecast last July."
Last July, Chadwick said, the rate of earthquakes was high and had been building but began to moderate again. And the area is still inflating "at a pretty healthy rate, but the rate is a little lower."
Earthquake activity, too, has also moderated.
"I would be more confident if the earthquakes were high," Chadwick said. "But it's totally possible that before the end of the year, I'll decide, ‘OK. We need to lengthen it a little more, but we’ll see."
WHERE IS THE LARGEST ACTIVE VOLCANO IN THE WORLD?
Would the US be impacted if the volcano erupts off the West Coast?
This map shows the location of the Axial Seamount on the floor of the Pacific Ocean within the "tectonic neighborhood" off the U.S. West Coast.
(FOX Weather)
While it's always important to have emergency supplies in case of a natural disaster or other situations, this isn't the time to run to the store and stock up on non-perishable food and batteries.
Back in December, a massive magnitude 7.0 earthquake was reported off the coast of California and Oregon, triggering a Tsunami Warning. That powerful earthquake was not associated with Axial, and even if or when it erupts, it will likely not have a direct impact on the millions of people living on the West Coast from Alaska to California.
"The eruption is not going to cause a tsunami because tsunamis are caused by a big, sudden movement of the sea floor," Chadwick said. "And, so, that doesn't happen in these eruptions. You know lava comes out and it flows, but it's a pretty slow process."
And in terms of the earthquakes that swarm the area ahead of an eruption – most are very small.
CAN ONE VOLCANO'S ERUPTION TRIGGER AN ERUPTION AT ANOTHER VOLCANO?
"And that won't have any impact on the Cascadia Subduction Zone, and they're not going to trigger a subduction earthquake," he said. "So, it's all very benign. There's not any hazard."
Finally, Chadwick concluded that there's so much interest in Axial Seamount because it's a great learning opportunity.
"It's this great natural laboratory," he said. "It's really active. So, you can test all these ideas about how volcanoes work, how eruptions are triggered, how magma gets to the surface during the eruptions. Whether we can forecast all these, so it's a great place for that kind of study."