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The fires below: burning coal sculpts landscapes worldwide - underground fires in coal seams

Science News, May 10, 2003 by Sid Perkins

In Centralia, Pa., the ground is prone to sudden and unexpected collapse. Hot, sulfurous gases waft from vents in the earth, kill trees, drive away wildlife, and sometimes threaten people's lives. Plumes of I smoke rise from cracks in a highway that's been closed for more than a decade. This once-bustling town isn't astride the gates of Hell, but instead sits atop an underground coal fire. In 1962, Centralia was home to about 1,100 people. In May of that year, someone set fire to the town's dump to make room for more trash, a common practice in the region. Unexpectedly, the fire flared for about a month. When workers scraped back the burning refuse, they discovered that the flames had ignited a subterranean coal seam.

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The fire continued to burn downward and by August had reached the network of old mine tunnels beneath the town. Carbon monoxide filled the tunnels and closed the mine where many people in Centralia had worked. Over the next 16 years, state and federal agencies spent more than $3.3 million to control the fire, with limited success. In 1983, the U.S. Office of Surface Mining, part of the Department of the Interior, released a study that estimated it might take another $ 663 million to extinguish the fire. It was far cheaper for the government to buy the town and relocate its businesses and residents.

Today, about 20 holdouts still live in Centralia, even though the government condemned their homes more than a decade ago. The last church in town has been razed, but its cemetery remains. The town is now so small that the U.S. Postal Service is taking away its zip code.

Stubborn underground fires like that in Centralia aren't uncommon in coal country. Any region with enough coal for a mine is at risk. There are dozens of coal fires burning out of control in Pennsylvania alone; worldwide, there could be hundreds of thousands. Some smolder deep within abandoned mines; others blaze forth in exposed seams of coal. Like forest fires, coal fires can be sparked either by natural phenomena such as lightning or by people's carelessness.

Beyond their potentially devastating effects on mining communities, coal fires change the landscape and damage the environment.

FIGHTING FIRE Coal fires can be difficult to extinguish. In Centralia, for instance, workers tried to smother the fire with fly ash-a byproduct of burned coal--but failed. Then, they attempted to dig a trench to isolate the burning coal, but the fire had advanced farther than they had expected.

The mine tunnels, as well as pre-existing fractures in the rocks, permit airflow to the fire, says Daniel H. Vice, a geologist at Pennsylvania State University's Hazelton and Schuylkill campuses. The configuration of the coal seam didn't help matters, either. The layers dip below the surface at angles between 35[degrees] and 60[degrees], making it difficult to dig trenches deep enough to get below the fire to isolate it.

The Centralia fire is an example of why it's important to attack coal fires early, says Steve R. Jones, a geologist at Pennsylvania's Bureau of Abandoned Mine Reclamation in Harrisburg. If fire-fighters arrive before a coal fire spreads across about 1 hectare--an area about 2.5 times the size of a football field--then the blaze can typically be extinguished for less than $500,000, he estimates. If the fire burns for a year or so and covers 5 hectares, then firefighting costs often exceed $1 million.

With funding from the U.S. Agency for International Development, Jones and a few colleagues from Pennsylvania, West Virginia, and North Dakota developed a training course that would help geologists worldwide analyze a coal fire to determine the best way to extinguish it.

For example, Indonesia suffered a spate of forest fires in 1998, when an El Nino brought drought to large regions of the western Pacific. Dry conditions allowed many agricultural fires to escape control, and some of those blazes ignited deep beds of decaying plant matter on the forest floor (SN: 11/9/02, p. 291) and subsequently lit coal seams.

Late in 1998, in the first stages of a 3-year pilot project, the scientists and local geologists conducted a coal-fire census and found 84 such fires still burning along a 120-kilometer highway that rims Borneo's eastern shore. That figure, extrapolated to the entire Indonesian coal-producing area, suggests that the country may have had up to 100,000 coal fires at that time. During the El Nino, the carbon dioxide and other greenhouse gases from those conflagrations probably rivaled the pollution spewed by the country's automobiles, says Jones.

He and his colleagues have trained about 100 students, who now are educating other Indonesians in firefighting techniques. Jones described the project and its early results in Denver at February's annual meeting of the American Association for the Advancement of Science (AAAS).

A SIMPLE RECIPE Coal fires, like all blazes, need three ingredients: oxygen, fuel, and heat. The key to putting out a coal fire is to remove one or more of those ingredients from the mix, says Jones.

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The fires below: burning coal sculpts landscapes worldwide - underground fires in coal seams

Science News, May 10, 2003 by Sid Perkins

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