Coal is a black rock composed of the altered and compressed remains of plant material that, by burial, escaped decomposition. It occurs in layers with other rocks at or beneath the earth’s surface.
Coal in Pennsylvania
Pennsylvania coal, until recently the state’s most abundant energy resource, has served the nation well. The economic coals in Pennsylvania are of two types:
Bituminous (“soft”) coal
Anthracite (“hard”) coal
The publication Coal in Pennsylvania (PDF) includes information about the geologic history of coal in the commonwealth, where it occurs, and how it is mined and used.
In Pennsylvania, operators mine coal at the surface and underground. The Pennsylvania Geological Survey has a page-size map (PDF) of the state’s coalfields. Some of the largest, most modern and productive underground coal mines in the United States are in southwestern Pennsylvania in the Main Bituminous coalfield.
Historically, humans used coal as the fuel of choice for transportation and other steam-powered applications. It was and still is essential, in the form of coke, for the production of steel.
Today, in addition to steel-making, coal is used in several ways. Utility power plants burn coal to produce electricity, and coal is used for heat and power in other industrial plants, residential and commercial heating, and specialty products such as activated charcoal for filtration.
The Pennsylvania Geological Survey, in cooperation with the U.S. Geological Survey, published a series of coal availability studies for the Main Bituminous coalfield of western Pennsylvania that estimate the coal resources available for extraction.
Within each area investigated, the authors used data on coal thickness obtained from drill holes, outcrops, and mine exposures, and information from maps showing the geographic extent of each commercial coal and their mined-out areas, to calculate the original volumes (or tonnages) of coal and the quantities still available for extraction.
The five 7.5-minute quadrangles for which reports have been published include Clymer (ZIP), Hackett (ZIP), Saxonburg (ZIP), Strattanville (ZIP), and Waynesburg (ZIP).
Over the years, the Pennsylvania Geological Survey released numerous maps and reports dealing with the occurrence and distribution of coals and associated mined-out areas. Related mineral resource reports and other publications can be downloaded from PaGEODE.