Axial Seamount showing signs of approaching eruption as magma builds up off Oregon coast

Latest observations by scientists at the University of Washington’s Cabled Array indicate that Axial Seamount, an underwater volcano off the Pacific Northwest coast, could be approaching its first eruption in a decade — possibly within months to a year if current trends continue.

Axial Seamount was the focus of one of the world’s first long-term underwater volcano observatories — the New Millennium Observatory (NeMO) — established by NOAA in the late 1990s. Today, the site is continuously monitored through the Ocean Observatories Initiative’s Regional Cabled Array, which provides real-time data via a network of submarine cables.

The system includes 20 seafloor instruments deployed around the volcano, collecting data on seismic activity, seafloor deformation, vent chemistry, and ocean conditions.

Data from the Cabled Array shows the seafloor has inflated more than 20 cm (7.9 inches) in recent months — approximately twice the rate observed prior to previous eruptions, including the 2015 event.

At the same time, scientists have observed a sharp increase in the number of small earthquakes on the seafloor. The volcano is also starting to bulge, which indicates magma is accumulating beneath the surface.

“The volcano has inflated more than 20 cm, and we’ve seen this inflation before — we know how it ends,” said William Wilcock, a professor of oceanography at the University of Washington. “We’re now within a few months to a year of an eruption.”

The volcano is following a well-documented pattern of inflation and increased seismicity that has preceded past eruptions. A similar buildup of activity was recorded in the months leading up to the 2015 eruption.

Researchers say there’s no need for public concern. According to Deborah Kelley, an oceanography professor at the University of Washington, most people would not even know an eruption was occurring if not for the monitoring infrastructure in place.

The team explained that underwater eruptions like this one typically do not cause tsunamis or major earthquakes. Kelley added that the thick layer of ocean above the volcano helps suppress explosive activity. She also noted that the magma beneath Axial Seamount contains fewer gases than magmas erupted on land, making submarine eruptions less violent.

Located about 480 km (298 miles) west of Cannon Beach, Oregon, Axial Seamount lies submerged at a depth of roughly 1 410 m (4 626 feet) beneath the ocean’s surface. It sits directly on the Juan de Fuca Ridge, an underwater boundary where tectonic plates are diverging and new seafloor is created. Within the ridge system, it is positioned between the Blanco Fracture Zone and the Cobb offset.

Over the past 25 years, Axial Seamount has erupted three times — in 1998, 2011, and 2015 — making it a key location for studying submarine volcanic processes and tectonic activity on mid-ocean ridges.

The most recent eruption occurred in late April 2015. It was first detected through a series of small earthquakes on April 23, signaling magma movement beneath the seafloor. Physical evidence of the eruption was collected during a research expedition in August that year.

Using seafloor mapping tools and a remotely operated vehicle, scientists identified fresh lava flows to the north of the summit caldera. Some of the flows were thick and showed signs of having collapsed inward while still partially molten. Additional thin lava deposits were found inside the northeastern part of the caldera and along its rim.