Mapping the coal fire at Centralia, Pa using thermal infrared imagery

Thermal infrared imagery (TIR) is being used to identify the location and intensity of heat released from mine fire vents in Centralia, PA. Recent TIR images collected from 2007, 2009, and 2010 have been combined with previously collected TIR airborne images and other data from 1971, 1980, 1981, 1982, 1983, and 2002-2003 to produce a map that reveals the thermal history of the region. Additionally, borehole data, direct observations, false color imagery and aerial photographs were used to locate fire location. The compilation of these images into one map provides a history of the progressive coal fire movement since it's ignition in 1962. The fire, which is thought to be located in the Buck Mountain coal bed (No. 5), at the base of the Llewellyn Formation (Middle Pennsylvanian), can be traced along the limbs of the eastwardly plunging Locust Mountain Anticline. It is moving west at a rate of less than 2 m/yr, which is down from estimates made in previous decades of nearly 20-23 m/yr. Along one of the main fire fronts, TIR images reveal circular to semicircular patterns that represent zones of subsidence as the fire advances. Temperature readings from the TIR imagery and ground measurements suggest a variable thermal history with a declining overall temperature. Today, temperatures at gas vents generally do not exceed 65 degrees C. Given the changes in the fire over the years, it is suggested that the fire is decreasing in intensity and rate of movement as it moves deeper into the subsurface. Additionally, it may be encountering subsurface chambers where the anthracite coal has been removed. Preliminary CO/CO2 ratio measurements at gas vents are inconclusive but suggest oxygen is present in the subsurface. A decrease in coal, perhaps due to the shape of the coal bed or its absence due to mining, is the primary limiting factor affecting the rate of movement and temperature of the fire. This limited resource may cause the fire to smolder before naturally extinguishing. Early estimates predicted the fire would burn for a century or longer. This study suggests that the fire may extinguish earlier than previously thought. (C) 2011 Elsevier B.V. All rights reserved.