Pennsylvania is at the northern end of the Appalachian coal basin. Approximately 15,000 sq mi (39,000 sq km) or one third of the state, is underlain by coal measures. The coal is Pennsylvanian to Permian in age, and includes bituminous and anthracite coal found in several separate fields.

The bituminous coals have dips of less than 2°, with some beds dipping up to 8° and rarely exceeding 8°. These steeper dips are found along the flanks of the major Plateau fold structures and in proximity to the Allegheny Front. Bituminous coal in the Broad Top field and in the anthracite basins have dips commonly exceeding 60°.

The earliest record of coal being mined in Pennsylvania was at Fort Pitt (now Pittsburgh) in 1761. To date, more than 22 billion tons of coal have been mined out or lost due to mining. Coal production in 1978 was 80,342,913 net tons of bituminous coal and 5,037,960 net tons of anthracite coal.

Recoverable reserves are estimated at 22 billion tons of bituminous coal more than 28 in. (71 cm) thick, and 8 billion tons of anthracite coal more than 24 in. (61 cm) thick. These estimates assume that all the major coals are continuous throughout their projected area of occurrence, as with the Pittsburgh seam.

However, recent detailed studies on the sedimentology of the Upper Freeport coal in southwestern Pennsylvania indicate that the stratigraphy of the coal-bearing measures may be more complex than previously believed. These units consist of a highly variable sequence of coals, clays, sandstone, shales, limestones, and other rock types occurring in lenses, pods, channel-fills, etc. Because of the presence of these coal-seam discontinuities in some of the coals, the current coal reserve estimates may be significantly inaccurate.

The Pennsylvania Geological Survey is currently cooperating with the U.S. Geological Survey in the National Coal Resources Data System. We are currently in the third year of the program to enter all point-specific data, including coal thickness and quality, into the computer. In addition, coal crop maps for each principal coal seam showing areas of deep and strip mining are being compiled. This program will result in much more accurate estimates of the remaining coal reserves in Pennsylvania.

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