USA — High atop a steep grass-covered mountain overlooking the Little Sespe Canyon near Fillmore, the earth is on fire.
Wisps of smoke rise from a brown patch of grass that looks like it was toasted under an oven’s broiler. Deep down, under the dirt, rocks and grass, something is smoldering and burning, sending smoke through cracks in the parched soil.
It’s being called a natural anomaly, a geological whodunit, a scientific puzzler. And it’s the second time that scientists have been scratching their heads over the fact the earth under Ventura County is burning.
In 2004, a patch of land northwest of Ojai burned so hot, it started a brush fire that scorched three acres in Los Padres National Forest. Firefighters cleared the grass from the newest area of hot earth near Fillmore on Friday so the same thing won’t happen..
Though the outcome of both circumstances is the same ground hot enough to delaminate boot soles the reasons they started are likely very different. But both are equally fascinating to those who make their living examining rocks and sediment.
“This is a lot of fun,” said Allen King, a former geologist with the U.S. Forest Service who has studied both sites. “I’m retired, but this is what I love to do.”
The leading theory behind the latest hot spot is that gas or oil or some other hydrocarbon deep in the soil caught fire and is burning, pushing ground temperatures to 812 degrees. What ignited it or when it started burning is a whole other question.
“We don’t know how long this particular thing has been burning,” King said.
Firefighters have responded to the area five times since 1987, at times dumping water into the ground to try to quash the flames. King said a landslide hit the area within the past 100 years or so, possibly creating enough friction to start a fire. Another theory is that the land is so dry and parched that all moisture has been sapped from the ground, making it more susceptible to ignition. King said it’s possible that some spark on land caused the underground blaze. How long it will burn is anyone’s guess.
Such fires aren’t uncommon in areas where there is a high concentration of gas or oil underground, he said.
But while the origins of this fire may be a relatively common phenomenon, the one near Ojai is still a puzzle.
“We’ve been researching it for a while and don’t have all the answers,” said Scott Minor, a U.S. Geological Survey researcher based in Denver who has made multiple trips to the site. “It’s like detective work.”
He and other scientists, including King, are hoping to publish a paper on their findings that may be a geologic first.
The anomaly was discovered after the land got so hot, it started a brush fire and burned three acres. Their theory is that there are high concentrations of pyrite commonly called fool’s gold deep in the earth that were oxidized and converted to another mineral when a flush of oxygen was introduced after a landslide. The oxygen could have come from new fissures in the earth.
The process of converting to a new mineral was an exothermic reaction, releasing heat that could have sparked old carbon-based material decayed wood or plants that started the underground blaze.
King stuck a thermometer 14 inches into the ground and got a reading of 550 degrees. One time, the ground was so hot, the glue holding the sole of his boots melted. Grass can burn at 300 degrees.
“After that we were more cautious about standing in one place for too long,” he said.
Minor said if a landslide were indeed a factor, it could be a new geologic discovery. The research group he’s working with would like to drill down into the earth to see if the materials support the theory but is faced with a few hurdles. The first is funding and the second is the fact that the area is in the Dick Smith Wilderness, where no machinery is permitted.
Until then, the scientists are having fun trying to solve the puzzle.
“It’s always neat when you explore something that is new and something that hasn’t been documented before,” Minor said. “It’s fun to speculate, but it’s a lot more satisfying when you can nail it down.”