Mysterious Hot Spot-Ventura CA - The Gates of Hell

A mysterious hot spot -- so hot it ignited a fire in a remote corner of Los Padres National Forest -- has stumped a dozen geologists who have trekked out to study it, amazed to see something they have never seen before.

The hot spot was discovered by Los Padres fire crews last summer after a hunter reported a column of smoke hovering over the ridgelines of the Dick Smith Wilderness in the rugged San Rafael Mountains. Fire crews were flown in to extinguish the fire, which had burned through about 3 acres of chaparral and piñon trees growing on a rocky canyon landslide.

It was a sunny day in the middle of August, void of thunder or lightning. What had started the fire? As the firefighters walked around, they noticed something strange.

"They saw fissures in the ground where they could feel a lot of heat coming out," Los Padres geologist Allen King said. "It was not characteristic of a normal fire."


A day or two later, the fire investigators went back to the canyon, this time armed with a candy thermometer. They stuck it into one of the cracks in the landslide. It hit the top of the scale, at 400 degrees.

The crew called Mr. King, and he made the three-hour hike into the badlands to see for himself. He dangled a long plastic strip into one of the cracks. Within seconds, it melted away into nothing.

So Mr. King called in Robert Mariner, a U.S. Geological Survey hydrologist who studies volcanic gas vents at Mt. Shasta, Mt. Hood and Mt. Rainier.

"When I heard about the candy thermometer, I was amazed," Mr. Mariner said, noting that the temperature of the volcanic vents he studies is typically 200 degrees, around the boiling point of water. "I thought these guys were pulling my leg."


It was no joke. Since August, Mr. King, Mr. Mariner and 10 other California scientists, including Jim Boles, a mineralogist at UCSB, have backpacked out to the hot spot looking for answers, lugging heavy equipment up and down the steep mountain slopes in 100-degree heat.

The scientists stuck long wire probes into the cracks and drove pipes into the ground to measure the hot temperatures. With the help of an air reconnaissance flight and thermal infrared imaging, they found that the hot spot patchily covered three acres, most of it overlapping the fire area.

The hottest spot of all was 11 feet underground, at 584 degrees -- a temperature that is hot enough to melt solder, an alloy of tin and lead. At just 4 inches down, the scientists found temperatures of up to 493 degrees. Paper and wood burn at 451 degrees.

The geologists began to joke about bringing in some tri-tip for a barbecue, instead of the granola bars and nuts they were eating. They wore hard hats and were careful where they stepped. Mr. King nearly lost the sole of one hiking boot because it came unglued on the hot rocks. He re-attached it with duct tape for the rough hike back.

The landslide itself was risky, too. It had probably occurred during El Niño rains of 1998 and was still active. New fractures recently opened around the top of the slide.

"It is still potentially dangerous to be walking on," Mr. King said. "And we think it could be a danger again in terms of forest fire. The grasses have grown back, and there still remains a potential for reignition."


The teams took the temperature of the hot spot in 22 locations, returning every couple of months to sample them all over again.

Surprisingly, they found that the rocks did not get significantly hotter, deeper down. During the past 10 months, the hot spot has cooled only slightly: The hottest sample has dropped from 584 degrees to 565 degrees.

Mr. Mariner visited the slide four times to study the composition of the gases coming out of the hot spot. He found carbon dioxide and carbon monoxide, the by-products of combustion.

"I keep expecting it to change suddenly, as the source of whatever we're burning is consumed, but it's changing slowly," Mr. Mariner said. "We're getting more oxygen in there."


Gradually, the scientists started narrowing down the possible causes. They found no oil and gas deposits or vents in the vicinity and no significant deposits of coal. The Geiger counter readings were normal for radioactivity, and there was no evidence of explosions or volcanic activity. Hot springs, a sign of geothermal activity, exist elsewhere in Los Padres, but nothing like that was happening here.

One possible explanation still under study is that an earthquake fault may be the source of the heat, Mr. King said, adding, "We can't rule out anything definitely yet."


But the likeliest theory, though still unproven, Mr. King said, is that when the landslide occurred, the slide broke apart the rock, creating a chemical reaction between oxygen in the air and minerals in the rock.

The rock, a type of shale, contains iron sulfides called pyrite and marcasite. When they are oxidized, the scientists theorize, the sulfides give off heat, burning the organic material in the shale -- the remains of dead plants and animals that were deposited into the mud on the ocean floor, 45 million years ago.

"Oxidation is combustion, but it's burning without the flame," said Mr. Boles, the UCSB geologist.

Perhaps it has something to do with the way the air is circulating through the landslide, he said. One thing that is puzzling, Mr. Boles said, is that there seem to be only small amounts of pyrite and marcasite in the rock.

He said that elsewhere in the world, waste piles in mining areas have been known to heat up and cause fires, but that is only where the rock contains high concentrations of sulfides.

"If we had found a coal bed in the landslide or a huge mass of marcasite or pyrite, we would have been a lot happier."

Mr. Boles said. "But we don't see anything obvious. It's hard to explain."


In August, the hot rocks ignited the roots of plants growing in the slide area, causing the forest fire. But scientists are at a loss to explain why no fires have occurred on hundreds of other shale landslides in Los Padres.

"What's so different about this one?" Mr. Boles said. "That's the question we keep asking, every time we go out there."


On their last trip to the Dick Smith Wilderness, the geologists dug up some of the hot rock, let it cool for an hour and stuffed it in their backpacks to send to U.S. Geological Survey labs in Denver. There, it will be analyzed with an electron microscope.

"We'll be able to determine whether there's enough sulfide mineral to support our theory," Mr. King said. "For a geologist, this is a very exciting find. We're not aware of any other features of this nature, where a landslide has started a fire."

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<A HREF="http://www.kron.com/Global/story.asp?S=3578869" target="_new"> Hot Spot Sparks Fire </A>


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