Are there mini volcanoes along California’s Coast? The Times investigates

The so-called “Hope Ranch Volcano” — as it’s known by locals — had again ignited, and it took crews hours to put out unwieldy flames and hot spots.

But experts say that description doesn’t accurately explain why this area routinely flares up — at least, geologically speaking.

No, it’s not a volcano, and while firefighters often refer to the spot as a “natural solfatara,” geologists say that isn’t quite right either.

“It’s spontaneous combustion,” said James Boles, a professor emeritus with UC Santa Barbara’s Earth Science Department.

When the earth layers of the cliffside move, oxygen can interact with unstable compounds in the rocks — including iron sulfides — which produces a lot of heat during the oxidation process. That heat can build so quickly and so high under the right circumstances that organic materials in the area spontaneously combust.

“Every couple years, the same thing happens,” Boles said. And while it might look like a mini volcano, it’s far from it.

This area has seen such flare-ups since the 1800s, according to a post from the Santa Barbara County Fire Department.

On Thursday, firefighters said the phenomenon caused a smoldering fire in an underground PVC drainage pipe, as well as significant flames and smoke off the hillside, the fire department said. Crews were able to stop any fire from spreading without causing damage to any structures..

The department referred to the natural process that causes the fire as a “solfatara,” a natural volcanic steam vent that releases sulfur gases, a term derived from a particular volcanic region in Italy. And while there are likely sulfur gases coming from the Hope Ranch cliffside, Boles said there is no underlying volcano, which makes the designation not quite accurate.

Interestingly, Hope Ranch is not alone.

Along Ventura County’s coast, locals have dubbed a geyser-like geologic formation the “Rincon Volcano,” but it appears also to be a case of inaccurate nomenclature.

At this spot, several hundred feet above the 101 Freeway between La Conchita and Rincon Point, the area has also spontaneously combusted during ground shifts, according to prior reporting from The Times.

The first recorded report of that “steaming mountain” was made in 1835 by a man traveling north by stagecoach to Lompoc, according to the Carpinteria Valley Museum of History.

Boles said similar processes can occur in a variety of locations, but certain rock formations are particularly susceptible to such… eruptions, if you will.

It’s worth noting that while there are currently no major volcanoes located along California’s Coast, there are several across the state.