Huge underwater volcano off major U.S. coast is set up erupt 'any day' as top scientists issue chilling warning | 1 May 2025 | The most active volcano in the Pacific Northwest could erupt "any day now," scientists have warn. The Axial Seamount is a mile-wide underwater volcano that sits 300 miles off the coast of Oregon and more than 4,900 feet below the surface of the Pacific Ocean. It last erupted in 2015, triggering roughly 8,000 earthquakes, producing 400-foot-thick lava flows and causing the bottom of the ocean to sink nearly eight feet.