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Abstract: Underground coal fires pose a threat to the environment and the health of those living in their proximity and can result in economic losses if these fires occur at mining areas. Design of methods to extinguish these fires requires that the extent of the subsurface fire be delineated. A conceptual picture of the workings of a subsurface coal fire near Durango, CO is presented first, which shows how the overburden above the burning coal seam can become heated. In high temperature and low O2 conditions, the heating of the overburden leads to the formation of magnetite, and its presence and the alignment of magnetic moments can be detected by a magnetometer. Magnetometer surveys allow high resolution areal mapping that differentiates among previously burned, currently burning, and unburned coal seam areas. The current and previous locations of the subsurface fire regions that are delineated by the magnetometer survey conducted at a fire on the Southern Ute Indian Reservation are consistent with various supporting data such as gas composition, temperature, and snowmelt data. [Copyright &y& Elsevier]

The Middle Pennsylvanian Herrin and Springfield coals contain the majority of the Illinois basin's resources. Many mining issues of these two seams are directly related to the geology of the region, including regional stress, faulting, and facies changes. Some of these conditions are widespread, while others are locally restricted. The long history of mining in these seams has been associated with many difficulties and hard-learned lessons related to mining geology especially concerning aspects of coal quality and roof geology along paleochannels, moisture-sensitivity in shales, fractures and "slips" in shales, floor heave, lateral stresses, clay dikes (veins), and coal balls. Both seams occur within classic "cyclothems," resulting from sequences of deposition between lowstand and highstand deposition. Transgressive, marine black shales and limestones blanket the coals across much of the basin, except near syndepositional channels where wedges of gray silty shale and interbedded shale and sandstone intervene between the coal and transgressive shale. Differences in the thickness, chemistry and strength of various shales in each sequence influence coal quality and roof conditions in underground mines. Associations of mining geology issues not specifically related to tectonics and horizontal stress, are (1) syndepositional channel and channel margin conditions, (2) post-depositional channels, (3) gray-shale wedge margins, and (4) marine shale roofs; especially where limestones thicken. Many of these features are similar to both seams, while others are more common in the Herrin, than Springfield Coal. Similar conditions occur above other coal beds in the Illinois Basin, as well as coal-bearing strata in other basins. Herein we review horizontal stress, fractures, coal quality, partings, coal balls, clay dikes (veins), dips and swales, floor heave, moisture sensitivity in shales, shale rolls, limestone bosses and cutouts, paleochannels and cutouts, stackrock conditions, paleoslumps, coal riders, kettlebottoms, and concretions in the roof. Hopefully, this summary will be useful for understanding seams with similar geology, but with less research on mining geology or shorter mining histories. • This paper reviews geologic factors which influence the mining geology of the Springfield and Herrin coals in the Illinois Basin. The long history of mining in these two seams has provided a wealth of data for understanding a variety of factors including lateral stress, faulting, floor heave, moisture-sensitivity in shales, paleochannels, channel margins, stackrock conditions, clay veins, kettlebottoms (in situ tree stumps), and paleoslumps. [ABSTRACT FROM AUTHOR]