Nearly 300 miles off the coast of Oregon, a massive volcano is showing signs of an imminent eruption. The 3,600-foot-tall, 1.24-mile-wide Axial Seamount is swelling and rumbling at the bottom of the Pacific Ocean.
This indicates that a massive amount of magma is building under the surface. Volcanologists expect the volcano to erupt before the end of 2025.
The important thing is that nobody’s very concerned about it. Mike Poland, scientist in charge of the Yellowstone Volcano Observatory, is excited that Axial Seamount will blow its top soon.
“This particular volcano is probably the best-monitored submarine volcano in the world,” he told Cowboy State Daily. “It’s fascinating and doesn’t really pose a hazard.”
Submerged Seamount
Axial Seamount is a shield volcano along the Juan de Fuca Ridge, a chain of undersea volcanoes extending between Oregon and Alaska. It is also one of the youngest known volcanoes in the Pacific Ocean.
Poland said Axial Seamount is similar to Mauna Loa, Earth’s largest active volcano, which is also a shield volcano. That’s why Poland and other volcanologists aren’t concerned about the imminent eruption.
“When Axial Seamount erupts, it’ll look a lot like a Hawaiian lava flow eruption,” he said. “It’s not an explosive eruption, but calm effusions of lava flowing out of the caldera and across the seafloor.”
For comparison, the Yellowstone “supervolcano” — a term Poland and other geologists don’t think is appropriate to describe the massive volcano — has a history of explosive eruptions. Its magma is thicker and more viscous, allowing gases to build up and lead to explosive eruptions.
While volcanologists are confident a Yellowstone eruption is highly unlikely, Axial Seamount has a history of frequent eruptions. Poland said eruptions of the volcano were observed in 1998, 2011, and 2015, and it has undoubtedly erupted several times before that.
“It’s frequently active,” he said. “Geologists monitoring Axial Seamount have observed that it reaches a certain threshold in terms of inflation, then it erupts. That inflation threshold provides a means of forecasting when an eruption might happen.”
Over the last few months, the seafloor around Axial Seamount has been inflating like a balloon. Based on the inflation threshold of previous eruptions, volcanologists anticipate an eruption before the end of the year.
Under Pressure
While shield volcanoes don’t erupt explosively, they can still cause tremendous destruction as their lava swiftly moves and destroys anything in its path. Fortunately, Axial Seamount doesn’t pose a danger to anyone.
The volcano sits under 4,626 feet under the Pacific Ocean. Its depth and the pressure of the overlying water mean the vivacious young volcano has some “performance issues.”
“Deep submarine eruptions are inhibited by the tremendous water pressure of the ocean,” Poland said. "Even explosive eruptions struggle against the ocean."
The magma that erupts from Axial Seamount will immediately be cooled by the ocean water, quickly forming a skin over the top of the lava flow that slowly cools it to its core. These are called pillow lavas, commonly observed at the surface when Mauna Loa lava flows reach the Pacific Ocean.
That’s another reason volcanologists aren’t concerned about the impacts of Axial Seamount’s imminent eruption. The lava has nowhere to go and will encounter tremendous pressure and cold water the moment it breaches the ocean floor.
Collecting a fragment of lava from a 2015 eruption of Axial Seamount with a robotic arm. (Monterey Bay Aquarium Research Institute) 
snowblower hydrothermal vent spewing hot water from Axial Seamount volcano. (Bill Chadwick, Oregon State University, copyright Woods Hole Oceanographic Institution) 
A vent in the Axial Seamount. (Canadian Scientific Submersible Facility and the University of Washington)
A Story Of Ice And Fire
Several different lava flows are exposed in Yellowstone National Park, but no pillow basalts. That’s because the Yellowstone hotspot has never erupted under several thousand feet of ocean water.
That doesn’t mean Yellowstone hasn’t erupted under enormous pressure. Poland said there’s evidence of subglacial eruptions that occurred around 150,000 years ago.
“The texture of lava flows, especially in the area of West Yellowstone, suggest that there might have been some subglacial volcanism or lava flows interacting with ice,” he said. “This is debated since the evidence is not cut and dry, but eruptions were happening when Yellowstone was very icy. So, it’s reasonable to think there were some interactions there.”
Compelling evidence of subglacial volcanism in Yellowstone is still standing in the Monument Geyser Basin, not far from Beryl Spring between Madison Junction and Mammoth Hot Springs. The “monuments” are sinter spires, similar to hydrothermal vents that form underwater.
Poland said the sinter spires at the Monument Geyser Basin could have been formed by subglacial volcanism, but more research is needed. Nevertheless, there’s a good chance that Yellowstone was under tremendous pressure while it erupted in the distant past.
“It's possible that we're seeing spires that would have formed as hot water and volcano gases rose to the surface and hit that ice,” he said. “We can't date them, so we don't really know, but there's definitely some evidence of interactions between ice and lava, and possibly even ice, water, and the hydrothermal system.”
Eyes Up
The ongoing inflation of Axial Seamount has reached the threshold of previous eruptions, so volcanologists expect an eruption soon. However, that doesn’t mean it’s a perfect system for prediction.
“The threshold is not perfect,” Poland said. “There’s some plus or minus to it, but the last few eruptions we’ve seen have reached or been near the threshold, and then an eruption has occurred. Based on the inflation rate of the volcano, it's in the zone for when eruptions would have happened previously.”
The United States Geological Survey installed a cable that feeds essential information to several monitoring instruments to monitor Axial Seamount. The agency also regularly measures and monitors the volcano, learning how it changes over time.
Axial Seamount and Yellowstone National Park are two of the best-monitored volcanoes in the world. Knowledge gained from one volcano can help scientists better under the other, along with other significant volcanoes worldwide.
Geologists might not know precisely when Axial Seamount is going to erupt. But when it erupts, they’ll know immediately, and Poland and many others will be watching with interest.
“Axial Seamount is not so dissimilar from the volcanoes in Hawaii and Iceland, except that it’s deep on the seafloor,” he said. “It’s a fascinating volcano, but there’s no hazards to be worried about.”
Contact Andrew Rossi at arossi@cowboystatedaily.com
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
