Far below the Pacific Ocean, about 300 miles off the Oregon coast, lies Axial Seamount, the most active underwater volcano in the Pacific Northwest. It’s slowly preparing for its next eruption. Scientists are carefully watching the volcano because it helps them understand how eruptions happen under the sea. Instruments on the ocean floor show that its caldera, the large crater at its top, is gradually rising, and the number of small earthquakes is increasing. These are signs that magma, or molten rock, is building up beneath the surface.
Since the last eruption in 2015, the seafloor above the magma chamber has lifted about 4 inches. Researchers from Oregon State University and the U.S. Geological Survey track these movements using pressure sensors on the seafloor. The volcano is now about 95 percent inflated compared to before the last eruption. Experts predict that another 8 inches of uplift could trigger the next one, possibly sometime between mid and late 2026. Although their earlier forecasts suggested it could happen sooner, the current data points to a slightly delayed event.
Lessons From the Past
The 2015 eruption of Axial Seamount was one of the most dramatic ever recorded under the ocean. Within just one day, the volcano generated more than 10,000 tiny earthquakes as magma forced its way upward. Lava poured out across 25 miles of the seafloor for about a month. Scientists were able to watch it unfold almost in real time thanks to deep-sea monitoring systems. This event became the standard model for what a future eruption might look like.
Axial Seamount has erupted several times in recent history, in 1998, 2011, 2014, and 2015. These events have helped scientists learn how submarine volcanoes behave over time. The pattern is quite consistent: after each eruption, the ground sinks as magma drains away, and then it slowly rises again as the magma chamber refills. The volcano lies on the Juan de Fuca Ridge, where two tectonic plates, the Pacific and the Juan de Fuca, are moving apart. This spreading pulls the crust open and creates the ideal setting for frequent volcanic activity.
Pressure Beneath the Waves
Even though the inflation slowed slightly after 2024, magma continues to collect beneath Axial Seamount. The chamber grows by roughly 10 centimeters a year, steadily adding pressure under the crust. Scientists know that this build-up cannot last forever. Eventually, the magma pressure will overpower the surrounding rock, leading to a new eruption.
The process is complicated. As magma fills the chamber, it compresses the rock above, raising the eruption threshold. At the same time, the tectonic plates around the ridge slowly move apart, releasing some of that pressure. This delicate balance determines when the volcano will finally erupt. The good news is that, despite all this activity, Axial Seamount poses no danger to humans. It sits nearly a mile underwater and far from the coast, making it too deep and too distant to cause tsunamis or ash clouds. When it erupts, the lava cools almost instantly upon meeting seawater, and gases dissolve safely into the ocean.
Watching and Learning From the Deep
Because of its frequent eruptions and easy access for researchers, Axial Seamount is one of the most closely studied volcanoes on Earth. The Ocean Observatories Initiative’s Regional Cabled Array, operated by the University of Washington, has built a network of undersea cables stretching hundreds of miles offshore. These cables connect sensors, cameras, and instruments that constantly send real-time data to scientists on land. Researchers can see how much the volcano inflates, track earthquake swarms, and even view live footage from the caldera floor. This high-tech system, funded by the National Science Foundation, makes it possible to monitor volcanic changes as they happen.
The volcano also supports a unique deep-sea ecosystem. Around its hydrothermal vents, cracks that release superheated, mineral-rich water reaching over 570°F, unusual creatures flourish in total darkness. Life here doesn’t depend on sunlight but instead on chemical energy from the vent fluids. Tube worms, crabs, and specialized bacteria thrive in these extreme conditions. When an eruption occurs, it can destroy some of these habitats, but new vents soon appear, allowing life to return and rebuild.
Despite all this technology, predicting exactly when Axial Seamount will erupt remains difficult. Its behavior can change quickly, and the patterns scientists have observed don’t always repeat perfectly. The rate of inflation, for example, slowed unexpectedly in 2025. Still, each new piece of data improves understanding. The next eruption will provide a rare opportunity to study how magma moves, how ecosystems recover, and how Earth’s powerful internal forces shape the ocean floor.