Pennsylvanian - About 323–299 million years ago · Countywide
During Pennsylvanian time, rivers and shifting lowland environments deposited sand and mud across the region. Burial and cementation turned these materials into sandstone and shale. These layers became part of the bedrock of the future county. Much later, erosion exposed resistant sandstone at places such as Coopers Rock, leaving cliffs and rock masses that visitors can see today.
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Read full entry and research notes →Pennsylvanian - About 323–299 million years ago · Countywide
Vegetation accumulated in waterlogged wetlands across the region during Pennsylvanian time. Some plant material survived decay as peat. Later, heat and pressure from burial transformed peat into coal. Repeated changes in the landscape left coal seams among layers of other sedimentary rocks. Those deposits, including the Upper Freeport coal in Preston County, would eventually become part of the county’s mining history.
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Read full entry and research notes →Pleistocene to present - About 2.6 million years ago to the present · Countywide
Long after the region’s rock layers formed and folded, rivers and streams have continued to erode them. The Cheat River, Preston County’s largest river, has carved a deep canyon and exposed soluble rocks, including limestone of the Greenbrier Formation. Groundwater has developed caves in these rocks, and sediments deposited within the caves preserve evidence that helps geologists reconstruct the river’s downward cutting. This period represents one chapter in an ongoing process, rather than a precise starting date for the canyon. The landscape visible today is one stage in a continuing history of change.
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