A unique geological phenomenon near Hope Ranch flared up again on Sunday, generating a small fire and a black cloud of smoke. 

At approximately 12:35 p.m., Santa Barbara County firefighters responded to the incident on a bluff above the shoreline near the Hope Ranch community, fire Capt. Scott Safechuck said. 

The fire was isolated to a plastic drainage pipe and surrounding vegetation, Safechuck added.

No structures were threatened. 

“This is ongoing historical activity that flares up periodically,” Safechuck said. 

Nicknamed the Hope Ranch Volcano, the phenomenon isn’t related to steam linked to magma.

Instead, a different natural geologic phenomenon causes oil shale trapped in sedimentary rocks to heat up and combust spontaneously, smoldering once exposed to oxygen.

The Hope Ranch site flares up periodically, sometimes igniting vegetation, and at other times demanding attention from firefighters to ensure that the area remains safe.