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Coal Geology

Miner and coal seam

Coal in Ohio

Coal-bearing rocks mapCoal is found in the eastern third of Ohio within rocks of Pennsylvanian age (323–299 million years ago) and in the younger overlying rocks of Permian age (299–252 million years ago). The Pennsylvanian rocks of Ohio are divided into the following groups (oldest to youngest): Pottsville, Allegheny, Conemaugh, and Monongahela (click the map to enlarge). There are approximately 58 named coal seams of varying thickness in Ohio.

How Coal Forms

Coal is formed from the accumulation of undecayed plant material that once grew in swampy mires over long periods of time. Burial of this plant material under sedimentary rocks generates heat and pressure, which in turn causes physical and chemical changes to the plant material. The material is first transformed it into peat and then into coal. If these conditions are maintained, the plant material can build up and attain substantial thicknesses and form layers, which are called seams.

Additional Resources

Coal Availability Mapping & Reports

Explore the links below to read recent coal availability studies. Or search our Publications Catalog.

Coal Measurement & Elevation Data

The Division of Geological Survey manages a large collection of information on Ohio coals, including:

  • Approximately 10,500 geophysical well logs.
  • 4,000 measured stratigraphic-sections.
  • 4,500 core descriptions.
  • More than 600 individual physical and chemical analyses.

These records have been added to the National Coal Resources Data System (NCRDS), which is maintained by the U.S. Geological Survey and provides a platform to make these records publicly available.

Operator Reporting Forms

2021 Coal Operator Reporting Form (pdf)

2021 Industrial Mineral Operator Reporting Form (pdf)

Further Reading

Download the publications below to learn more about Ohio coal geology. Or search our Publications Catalog.

Learn more about Ohio coal production and economic information on our Industrial Minerals web page.