CAPE MENDOCINO – A strange-shaped, 3,300-foot-tall underwater volcano has been discovered just 184 miles off the Northern California coast.

The sea mountain, or "seamount," appears more like a smooth-sided circular tower, with near-vertical sides, than a craggy mountain. It was found in February by an ocean mapping autonomous sailboat as part of a multi-agency survey led by the National Oceanic and Atmospheric Administration.

"Typically seamounts have sloped sides, like Mount Fuji," Dr. Aurora Elmore, the program manager for NOAA's Ocean Exploration Cooperative Institute, told SFGATE. "But what's interesting about this one is that it's really steep. It rises from the bottom of the seafloor with a tower shape."

Elmore thinks this unique shape may be because the volcanic activity that formed it was "super hot, and happened all at once." Alternatively, the structure may have lost a more gradually sloped base due to a build up of sediment known as "marine snow," or as Elmore puts it: "Millennia of fish poop."

The find is an anomaly for another reason, too. While there are 63 identified seamounts off the California coast, there are none near the one found off the coast of Cape Mendocino. "It doesn't fall into the area of known seamounts," Elmore says. "It expands the range."

The 1,200-foot-deep crater at the summit of the new underwater volcano sits about 2 miles below the ocean's surface, and was found through the use of a vessel operated by Bay Area ocean research company Saildrone, in partnership with NOAA and other agencies.

Story Date: April 6, 2023