Axial Seamount, an underwater volcano off the Pacific Northwest coast, could erupt soon for the first time in a decade. Scientists at the University of Washington have detected a sharp increase in small undersea earthquakes and seafloor inflation — signs of magma buildup within the volcano. Despite the activity, experts say there is no threat to coastal communities. The site remains under constant observation through one of the world’s most advanced ocean monitoring systems.

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.

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 Regional Cabled Array spans the entire Juan de Fuca tectonic plate, from the Oregon coast to the summit of Axial Seamount 480 km (300 miles) offshore. Credit: Ocean Observatories Initiative.

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.