KENTUCKY—THE OTHER LAND OF ARCHES

Kentucky has the most natural arches (rock openings) in the eastern United States with openings occurring in a variety of physiographic regions and geologic units. Natural rock openings occur on ridge tops which form along narrow ridges bordering stream valleys, along cliff sides, along ridge sides, in stream valleys, and in sinkholes across the state. In Kentucky’s two coal fields, openings form dominantly in thick, cliff-forming, jointed, crossbedded, sandstones. In other areas, openings may occur in jointed sandstone or limestone. Karst-associated openings occur in several limestone units. Most of the rock openings in the state occur in the Lower Pennsylvanian, cliff-forming, Corbin Sandstone Member of the Grundy Formation, on the western margin of the Eastern Kentucky Coal Field. The longest span of any rock opening measured is 165 ft (50 m) along a cliff-side opening in an outlier of the Lower Pennsylvanian Caseyville Formation (sandstone) in the Fluorspar District of the Mississippian Plateaus region of western Kentucky. The highest clearance measured is 85 ft (26 m) along a stream valley underlain by limestone of the Slade Formation (Middle Mississippian) in southeastern Kentucky in the Eastern Kentucky Coal Field, and the longest width measured is 193 ft (59 m) in northeastern Kentucky in limestone of the Slade Formation (Middle Mississippian) in a stream valley at Carter Caves State Park in the Eastern Kentucky Coal Field.

Many of the natural rock openings in Kentucky are featured in state parks, nature preserves, and natural areas, and provide economic, historical, aesthetic, and scientific value. These openings have become historical points of tourism, and thus are integrated components of local culture, history, and economy. Additionally, the openings are frequently photographed landscape features. Petroglyphs and hominy holes from indigenous people can be found along some of the cliffs that host rock openings. The longest span in the state occurs in the Mantle Rock Nature Preserve in Livingston County, near the Ohio River, in western Kentucky, accessed via the Trail of Tears. Preservation of natural rock openings on public lands provides an opportunity to research their evolution and continued development.