Among places where man has broken the earth for useful materials only quarries exceed coal mines in number and extent. The Midwest is particularly rich in bituminous coal mines, from central Illinois southeast into Indiana and Kentucky, and from mid-Iowa through western Missouri, eastern Kansas and on into Oklahoma and Texas. Another broad belt of fields rises in western Pennsylvania and spreads across West Virginia into eastern Kentucky and Tennessee down into Alabama. Colorado and Utah possess smaller fields. Northward from Colorado lie fields of subbitumi-nous coal and lignite.
Coal deposits formed on the borders of the basins of inland seas, where brackish swamps with abundant vegetation existed. Where the waters were deep, limestone was deposited, often in thin strata crowded with fossils of brachiopods, clams, gastropods, crinoids, and cephalopods. As the seas drained away, the jungle flourished and then died, leaving thick masses of organic material that later became coal.
Coal mines are either shaft or strip mines. Coal seams no more than a hundred feet below the surface can be profitably mined by stripping away the overlying soil and stone to expose the coal seams at the bottom of a great pit. The coal is scooped into trucks or railroad cars and hauled away. Such mining is less costly and less dangerous than underground shaft mining, where there is always the peril of poisonous fumes or explosive dust. There is a further advantage in that all the coal can be recovered; in shaft mines, coal must be left in the form of pillars to hold up the roof.
Strip mines are usually spread over a huge area ripped into rows of herringbone hills and small ponds. In time, such a region loses its raw, gashed hideousness; trees cover the hills, and the small lakes become fishing and recreation assets. Old strip mines are designated as such on
topographic maps and are concentrated along the swampy shoreline of the ancient basin. The largest coal field, the Illinois basin, has been strip-mined along the Indiana-Illinois border from Danville, Illinois, to Kentucky, across southern Illinois and then northward along the western Illinois line to a point opposite to Danville, as well as east and west along the Illinois river through La Salle and Fulton counties. The central part of the basin is mined by shafts to reach deeply buried coal.
Southern Iowa from the middle of the state to the western border also has many strip mines, and there are some in nearby states, as well as in southern Michigan, Pennsylvania, and other Appalachian states.
An operating strip mine will have a plant office where permission should be obtained, even to enter abandoned workings. The collector may be asked to sign a release form to relieve the operator of responsibility for injury. Strip mines present certain dangers. Vertical walls rise steeply,
Coal strip mine in action. Big dragline scoops up the gray shale overlying the coal and piles it to one side. Dugger, Indiana.
After weathering, the concretions litter the surface of the strip mine dump. Many will contain fossil ferns. Near Terre Haute, Indiana.
and the edge may have been shattered by blasting. The weight of a few persons near the edge may start a rock slide. The weathered shale becomes slippery in wet weather, and an unlucky collector may slide into the deep, cold water of a pit if he is not careful.
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