CENTRALIA MINE FIRE COLLECTING EXTRAVAGANZA WITH NATIONAL GEOGRAPHIC
The Centralia fire began when burning trash in an abandoned strip-mining cut, used as an unregulated dump at the edge of town, ignited anthracite in the Buck Mountain seam concealed behind the refuse. The fire then spread along the seam to coal mine tunnels beneath Centralia. Today, about 20 people are left in a town and its environs damaged by toxic gases, scorched woodlands, subsidence, and polluted streams.
Anthracite fires generate enormous amounts of heat energy and after more than four decades of burning, temperatures as high as 540°C were recorded in Centralia in 2003. Reconnaissance of the area with the National Geographic film crew for dramatic film footage revealed abundant mineral condensation products adjacent to vents and fissures in the Pennsylvanian Llewellyn formation, from which hot gases were exhaled at the surface. The minerals were found in association with the cemetery and death-valley "fronts," along which the fire is currently active. Condensation occurred when vented gas cooled below the gas-liquid transformation temperature as it encountered heat sinks such as sediment, rock, and vegetation. During mineral and gas collecting, evidence was found for two thermodynamic transformation paths. Fluffy mineral encrustations suggest that a gas to solid transformation (sublimation) occurred whereas "flow condensates," suggest a gas to liquid transformation occurred, followed by a liquid to solid transformation (freezing).
Field analysis of gas samples using a Drager hand pump and tubes revealed toxic concentrations of CO (2200 ppm) and CO2 (1000 ppm) whereas gas samples extracted from vents into Tedlar collection bags yielded, upon analysis, analogous concentrations of CO and CO2 in addition to a variety of sulfides, sulfates and hydrocarbons.