Coal Fires

Origin of Coal Fires

Sinkholes such as this one due to an underground mine fire in Renton Centralia, Pennsylvania may develop without warning, resulting in injury or death.

Coal Fires and Detail of Centralia, Pennsylvania

Coal fires in abandoned mines, in waste banks, and in "unmined" outcrops constitute serious safety and environmental hazards. Subsidence, the emission of toxic fumes, and deterioration in air quality create an unsafe and unpleasant atmosphere that can consume resources and depress property values for affected land and adjacent areas. Fires in abandoned mines and waste banks often affect people who had no connection with the actual mining.

Coal fires occur in almost every coal-bearing area and have been a problem for hundreds of years. In 1765, a fire was started in the Pittsburgh seam in Centralia, Pennsylvania. This fire was active until at least 1846. In the Western United States, coal-outcrop fires were a natural feature of the landscape. In 1805, Lewis and Clark, in their exploration of the Missouri River, reported that coal seams were plainly visible in the bluffs along the river and that some of the veins were burning, ignited by spontaneous combustion or grass fires. In south eastern Montana, an outcrop fire in a 6m (—20fi) thick seam has propagated —1524 "m" (5000 ft) along a small drainage basin (Kroll, 12).

The fire has affected a total area of 500 acres and has been burning for estimated 400 600 years. Hundreds of natural coal-bed fires are burning in the PRB. The age of zircons in associated clinker indicates that such fires have been occurring in this area for thousands of years. Coal fires associated with the abandoned or inactive coal mines is reported from mining areas around the world. Surface expressions of underground coal fires observable in the field include baked rocks, areas of dead vegetation, land subsidence, and gas vents and fissures with encrusted minerals (DeKok, 56).

The rank of a coal is also a factor in the incidence of coal fires. Lower-rank coals tend to be more susceptible to spontaneous combustion. Although lignites and sub-bituminous coals are more prone to spontaneous combustion, spontaneous combustion in higher rank coals can be supposed from the number of fires in which no other cause is suggested.

Natural barriers to subsurface fire propagation include faults where vertical displacement disrupts the continuity of the coal bed. Boundary pillars are considered natural barriers to fire propagation because solid coal seams do not ...