Coal

Coal is a general name used for black deposits consisting chiefly of carbon compounds derived from plants and plant debris that have been compacted into firm, brittle rocks.

Coal has either a dull or shiny luster and is divided into three main grades: anthracite (hard coal), bituminous (soft coal), and lignite. Most coal in Kansas originated during the Pennsylvanian Period, sometimes called the "Great Coal Age." During the Pennsylvanian, the eastern part of Kansas stayed nearly at sea level. Great swamps covered the low-lying areas along the coasts, and primitive plants, including ferns as tall as trees, grew densely. After the plants died and fell into the marsh, they were covered by water and mud and sand. As layers of sediment accumulated above the decaying plant material it was compacted, eventually producing the sedimentary rock, coal.

Geologists estimate that it took about 10 feet of leaves, tree trunks, and other organic matter to produce a one-foot layer of coal. The first stage in the transformation of decaying plant material into coal is the development of peat. Following long intervals of time, peat is transformed into lignite (brown coal) and eventually into bituminous coal. Had Kansas coal undergone even more heat and pressure, it might have become anthracite.

drawing of Pennsylvanian coal swamp

Coal is most likely to form from deposits in swampy areas with heavy vegetation. Coal takes millions of years to form.

Anthracite is a dense, brittle coal with either a shiny or dull luster and a shell-like (conchoidal) fracture. It burns with a pale-blue, smokeless flame. Anthracite has never been found in Kansas.

Bituminous coal, though soft, does not crumble on exposure to air. It breaks into irregularly shaped blocks, has a luster varying from dull to fairly bright, and burns with a yellow flame. Most coal in Kansas is bituminous and is found in the eastern third of the state.

color photo of chunk of bituminous coal

Bituminous coal from southeastern Kansas.

Lignite contains well-preserved plant structures (such as ferns, horsetails, and club mosses), showing that it originated in swamps. It is intermediate in quality between peat and bituminous coal. As much as 40 percent water, lignite dries out when exposed to air and crumbles. In Kansas, small quantities of lignite occur in Cretaceous rocks from the Dakota Formation.

Coal mining has played an important role in the region's economy. The outcrops of coals from the Cherokee Group extend from Columbus, Kansas, northeasterly into Missouri and Iowa.

color photo of rock outcrop with black coal seam clearly visible at base

Mulky coal bed from the Cabaniss Formation (part of the Cherokee Group) in Bourbon County.

Sources

Brady, Lawrence L., and Hatch, Joseph R., 1997, Chemical Analysis of Middle and Upper Pennsylvanian Coals from Southeastern Kansas: Kansas Geological Survey, Current Research in Earth Sciences, Bulletin 240, p. 43-59.

Buchanan, Rex C., and McCauley, James R., 1987, Roadside Kansas--A Traveler's Guide to Its Geology and Landmarks: Lawrence, Kansas, University Press of Kansas, 365 p.

Evans, Catherine S., 1988, From Sea to Prairie--A Primer of Kansas Geology: Kansas Geological Survey, Educational Series 6, 60 p.

Wilson, Frank W., 1978, Kansas Landscapes--A Geologic Diary: Kansas Geological Survey, Educational Series 5, 50 p.

Text by Liz Brosius, Kansas Geological Survey. Unless noted otherwise, illustrations by Jennifer Sims, Kansas Geological Survey; photographs by John Charlton, Kansas Geological Survey.

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