New Seamount discovered off coast of California

[Astronuc]

A 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.

https://www.yahoo.com/news/startlingly-round-formation-steep-smooth-141125280.html

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.

“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.

 

[Bystander]

https://www.yahoo.com/news/startlingly-round-formation-steep-smooth-141125280.html

"...none are active...." Now they've done it.

 

[Mark44]

"...none are active...." Now they've done it.

Not to worry...
California at one time many millions of years ago had lots of volcanic activity, due to the subduction of the Farallon Plate. Subduction continues to this day with remnants of the Farallon Plate, but only well north of San Francisco (Juan de Fuca Plate) and south of the southern tip of Baja California (Rivera and Cocos Plates). Plate motion for most of California is lateral, so there is no heavy seabed rock being subducted and heated to form magma that can feed volcanoes in this region.
North of there is a different story, as the video of magma activity below the Three Sisters and relatively recent eruption of Mt. St. Helens show.