Geologic temper tantrum
Coal seam blaze caused spectacle in Durango, hot dogs included

Investigators have yet to settle on a cause of the devastating Marshall Fire that tore through grasslands, strip malls and housing developments outside of Boulder late last year. They have ruled out lightning and downed power lines, but continue to look into the possibility that it was ignited by a coal seam fire. That got me thinking about coal fires and a moving mountain.

At any given time, thousands of fires smolder in abandoned, active mines and un-mined coal seams nationwide. Sometimes these subterranean blazes are sparked by lightning or wildfires. Other times, air and water get into the seam catalyzing an exothermic reaction that causes coal spontaneously to ignite. The fires can burn for hundreds of years or even longer. Most go largely unnoticed. That is, until they do something that demands attention – like start a wildfire.

The Marshall Fire began near the abandoned Lewis coal mines near Marshall, an unincorporated area northwest of Superior. Colorado geologists first observed an active coal fire here in the 1980s, but it is not uncommon for subterranean infernos to migrate to the upper world. In 2002, a coal seam fire started a 12,000-acre blaze near Glenwood Springs and at least one of last summer’s Montana fires has been traced back to a burning coal seam.

Sometimes the underground fires manifest in even more dramatic ways.

In December 1932, a triangular ridge south of Durango called Carbon Mountain, in what is now the Bodo Wildlife Area, moved. Actually, it kind of erupted, albeit not in a volcanic sense. “The whole hill is quaking, grunting, groaning,” a Durango News reporter wrote on the day of the calamity. “Boulders large and small and hundreds of tons of earth continue toppling from the crest of (Carbon) Mountain. Every few minutes, a great cluster of boulders would break loose. Clouds of dust marked their pathway as they shot out into space, landing in the valley to the north.”

The next morning, hundreds of folks headed out to the once-unremarkable hill, located where the Animas River slices through the Hogback Monocline, to witness the geologic temper tantrum. Others flocked in from out of town, out of state and even abroad. Popular Mechanics magazine sent someone to report back on “this huge mass of rock and earth, apparently loosened by some mysterious, subterranean disturbance … unlike any other such earth movement known to scientists.” Someone captured the movement on film. A young man set up a hot dog stand near the mountain’s base to capitalize on all the gawking. Even Will Rogers, during a visit to the town, piped in, suggesting that a bit of dynamite under the feature would keep it moving – and keep the tourist dollars flowing.

Newspapers would call Carbon Mountain the “playboy peak,” “galloping steed” and “bucking bronc” of the Rockies. Some called the cantankerous hill “Democrat Mountain” and the debris flow on its north face “Hoover Slide.” But the name that stuck for decades and that my grandmother used to refer to the hill when I was a kid was “Moving Mountain.”

Once the harebrained theories of the causes – vulcanism, West Coast tremors and exploding bootlegger stills – were cast aside, the serious work of figuring out what was going on began. John W. Vanderwilt, with the U.S. Geological Survey, declared that all the hype was nonsense and attributed the mountain’s shimmies to a run-of-the-mill landslide caused by surface water seeping into clay shale and making the sandstone layer on top slip.

Others had a counter-theory: A burning coal seam met up with pockets of associated methane gas. The gas exploded and the ground subsided, leading to slope instability and “jazz movements,” as one headline described the phenomenon. This would better explain the explosions, sulfurous odor emanating from the mountain, quickly melting snow on the north-facing ridge and small wildfire that broke out atop the ridge.

At the time, coal seam fires were burning all over the West. In May 1933, a week after another Moving Mountain episode, President Franklin D. Roosevelt said he was sending 200 members of the forest conservation corps to the Little Thunder Basin near Gillette, Wyo., to fight coal fires. “Colorado’s flaming Carbon Mountain is only one of over 100 uncontrolled fires that have been eating away at one of our national resources for years,” the Associated Press reported at the time. “In 28 coal fires (across the West’s public lands) carefully studied in 1928 and 1929, the coal endangered was shown to have a value in excess of $62 million.” 

The coal fire-methane theory also fits with the unusual geology of the Hogback Monocline. The layers of rock are tilted upwards here, like the rim of a big, shallow bowl, exposing the Fruitland coal formation. That opens a pathway for oxygen to fuel coal fires and allows methane within the coal seams to ooze into the air, leading to seemingly supernatural events. There are tales of campfire embers igniting the Pine River near where it cuts through the Hogback and folks lighting methane seeps as a sort of natural holiday light display. And then there was this one: “A married man who enjoyed his liquor would return home after a night out on the town only to find that his wife had locked him out. … He would light methane flowing from a vent pipe attached to the main casing of a water well to produce heat to keep warm.”

After oil and gas companies started drilling for this coalbed methane in earnest in the 1980s, the methane emissions along the Hogback Monocline increased, most likely because drilling liberated the methane. People also began noticing more coal seam fires along the Hogback around this time. 

In 1998 alone, three underground coal fires were discovered along the Hogback on Southern Ute land, along with evidence of prior fires, indicating they were a natural and fairly common occurrence (lending further credence to the Moving Mountain theory). Coal seam fires are notoriously difficult to extinguish. In 2000, the Southern Ute Tribe spent $865,000 trying to put out one of the aforementioned fires, injecting 4,400 cubic meters of foamy cement into the seam. It didn’t work.

Researchers theorized that methane within the coal seam may have been fueling the fire; cut off the fuel and you could possibly stifle the blaze. So they dug a “picket fence” of wells upstream of the coal fire to intercept the gas, which is put into a gathering system, processed and piped to market. Today, the project captures some 250,000 cubic feet of methane per day, robbing the fire of critical fuel and keeping a substantial amount of potent greenhouse gas out of the air. It also earns the tribe – a major energy developer in its own right – carbon credits.

The Land Desk is a newsletter from Jonathan P. Thompson, longtime journalist and author of River of Lost Souls, Behind the Slickrock Curtain, and the newly released Sagebrush Empire. To subscribe, go to: www.landdesk.org.