Startlingly round formation with steep, smooth sides found on seafloor off California

A mountain would seem to be a tough thing to miss, but a new one has been found off the coast of Northern California.

The seamount, as underwater mountains are called, was discovered by a seafloor mapping drone and its shape is more like a giant tower than a mountain.

It rises about 3,300 feet, has “relatively steep, smooth sides” and is rounded, with a diameter of nearly 3,000 feet, officials say.

Saildrone, the research company that found it, reports the mount sits 184 nautical miles off Cape Mendocino, which is about 300 miles northwest of Sacramento.

“The immediate reaction from the team was that it looked like a Bundt cake. It’s very round and with steep sides and a curved top that slopes into a crater in the center,” according to Neah Baechler, the lead surveyor for Saildrone.

“One side of the top rim is higher than the other, forming a gradual summit. ... The top is slightly bulbous, due to variability in slope.”

The summit of the seamount is about 11,352 feet below sea level. Meanwhile, the crater at the top of it is 1,200 feet deep, data shows.

Saildrone discovered the seamount while mapping the seafloor in a partnership with the National Oceanic Atmospheric Administration and the Bureau of Ocean Energy Management.

The seamount rises about 3,200 feet, has “relatively steep, smooth sides” and is rounded, with a diameter of nearly 3,000 feet, officials say.
The seamount rises about 3,200 feet, has “relatively steep, smooth sides” and is rounded, with a diameter of nearly 3,000 feet, officials say.

A ‘surprising’ find

Previously collected radar and satellite data hinted something might be sticking up off the seafloor in the area, “but the seamount turned out to be one much larger feature,” Saildrone reports.

“Discovering a new seafloor feature is always noteworthy, but this feature is wedged between the Mendocino and Pioneer fracture zones, placing it in a very dynamic area,” Baechler said.

“It’s surprising that no one has explored it, considering the many interesting fault-related features in the area and its proximity to so many ocean science institutions.”

Scientists assume the formation is the result of volcanism. Most seamounts form at volcanic “hotspots” — near the tectonic plane boundaries — and are believed to be extinct volcanoes, according to NOAA.

“Typically, they are cone shaped, but often have other prominent features such as craters and linear ridges and some, called guyots, have large, flat summits,” NOAA reports.

“There is a broad size distribution for seamounts but to be classified as a seamount, the feature must have a vertical relief of at least 1,000 meters (3,300 feet) above the surrounding seafloor.”

The U.S. Geological Survey reports “there are at least 63 seamounts” off California, and most of them are 100 miles offshore and a mile deep. It’s estimated they are 10 million to 25 million years old, and none are active volcanoes, the USGS says.

More discoveries await

Saildrone found the new mount in February, during a mission to map “previously unexplored areas around Alaska’s Aleutian Islands and off the California coast,” officials say.

Brian Connon, vice president of ocean mapping for Saildrone, called the seamount a “prime example” of the discoveries waiting to be found in U.S. waters. Among the extremes encountered during the mapping expedition was a spot in the Aleutians that was roughly 4.4 miles deep, Connon said.

“No shipwrecks were noted during during data collection, but we did see a whole array of fascinating features, including long finger ridges, likely from faulting with intricate drainage textures, submarine canyons and basins, and the Aleutian trench,” Connon said.

Saildrone intends to submit data about the seamount to the General Bathymetric Chart of the Oceans Sub-Committee on Undersea Feature Names for naming, so it can be added to international maps as a named feature.

The company is considered “the world leader in providing ocean data solutions with autonomous surface vehicles,” including uncrewed missions to survey conditions inside hurricanes.

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