Pittsburgh coal seam
The Pittsburgh Coal Seam is the thickest and most extensive coal bed in the Appalachian Basin; hence, it is the most economically important coal bed in the eastern United States. The Upper Pennsylvanian Pittsburgh coal bed of the Monongahela Group is extensive and continuous, extending over 11,000 mi2 through 53 counties. It extends from Allegany County, Maryland to Belmont County, Ohio and from Allegheny County, Pennsylvania southwest to Putnam County, West Virginia.
This coal seam is named for its outcrop high on the sheer north face of Mount Washington in Pittsburgh, Pennsylvania, and it is considered to form the base of the upper coal measures of the Allegheny Plateau, now known as the Monongahela Group. The first reference to the Pittsburgh coal bed, named by H.D. Rodgers of the First Geological Survey of Pennsylvania, was on a 1751 map.
The section of the Pittsburgh seam under the Georges Creek Valley of Western Maryland is known as The Big Vein This is isolated from the rest of the Pittsburgh seam by Savage Mountain (part of the Deer Park anticline), the Negro Mountain anticline, the Laurel Hill anticline, and the Chestnut Ridge anticline. Between these anticlines, the strata containing the Pittsburgh coal have been almost obliterated by erosion. The exception is a small remnant in Somerset County, Pennsylvania, in the Berlin Syncline between Negro Mountain and Savage Mountain.
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