Researchers discovered that massive lava flows and collapsing lava ponds at Axial Seamount reveal how underwater eruptions reshape the seafloor.
Volcanic eruptions pose serious geologic risks. Submarine volcanoes are especially difficult to observe directly, yet they are central to shaping the ocean floor and can generate tsunamis that threaten nearby coastlines.
The Juan de Fuca Ridge stretches for about 500 kilometers (310 miles) along the northeast Pacific, just off the coasts of Oregon and Washington. Along this ridge sits Axial Seamount, an active underwater volcano that has erupted multiple times since its discovery in the 1980s.
For more than two decades, teams from MBARI’s Seafloor Mapping Lab and Submarine Volcanism Team have investigated this site using autonomous underwater vehicles (AUVs) to map terrain and remotely operated vehicles (ROVs) to gather samples and direct observations. Their latest results were reported in Geochemistry, Geophysics, Geosystems.
Detailed mapping revealed three exceptionally large lava flow fields extending along the volcano’s distal rift zones. Each covers between 65 and 100 square kilometers (25 to 39 square miles) and reaches thicknesses of up to 130 meters (427 feet). Within these flows, scientists identified a network of deep, connected lava ponds that have no clear equivalent either on land or elsewhere on the seafloor. The study provides new insight into how these unusual structures developed.
Lava flows inflate, collapse, and reshape
The lava flows expanded outward and then thickened, a process known as inflation, after their forward movement slowed while molten material inside continued to rise and spread. This internal pressure caused the surface to bulge, overflow, and fracture. When sections of the solidified crust gave way, deep pits formed as the roofs collapsed. Some of the lava ponds remained molten until structural breaks allowed the liquid rock to drain away.
These large eruptions were supplied rapidly through dikes connected to the volcano’s summit magma chamber. Evidence suggests that the most recent of these events, around 1,200 years ago, may have coincided with a dramatic collapse of the summit caldera. The older lava fields appear to have formed through similar processes and may also be linked to earlier caldera collapses.
Reference: “Voluminous Inflated Lobate Flows on the Distal Rift Zones of Axial Seamount, Juan de Fuca Spreading Ridge” by Jennifer B. Paduan, David A. Clague, David W. Caress, Ryan Portner, Morgane Le Saout and Brian Dreyer, 23 January 2026, Geochemistry, Geophysics, Geosystems.
DOI: 10.1029/2025GC012675
This work was supported by grants to MBARI from the David and Lucile Packard Foundation.
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