The Land Itself, Karst, Cave Country, and the Shape of Kentucky

Drive across Kentucky long enough and you begin to feel the geology working on you. The state is divided into physiographic regions as distinct as different countries: the flat western coalfields, the pennyroyal plateau of the south-center, the limestone ridges of the Knobs, the rolling Bluegrass basin of the interior, and the corrugated Appalachian ridges of the east. Each region was settled differently, farmed differently, and feels different from inside a moving car.

The central and south-central part of the state sits on one of the world's great karst landscapes, terrain shaped by the dissolution of soluble limestone bedrock over millions of years. Karst produces sinkholes, disappearing streams that plunge underground and resurface miles away, and caves. A lot of caves.

The Mammoth Cave system, running beneath Edmonson and several adjacent counties, is the longest known cave system on earth, more than four hundred miles of surveyed passage, and surveyors are still finding more. The system has been explored by people for at least four thousand years; mummified human remains and woven sandals found inside it date to roughly two thousand years before the common era. The Ohio River, forming the entire northern border of Kentucky, is not merely a geographic feature.

It was the practical definition of freedom for much of the nineteenth century, a commercial highway through the eighteenth, nineteenth, and twentieth, and the route by which Kentucky connected to the wider American economy. The Falls of the Ohio at Louisville, the only significant drop along the river's course, forced the establishment of a portage and eventually a canal, which is why Louisville exists where it does. The eastern mountains are old, some of the oldest exposed rock in North America, worn down by erosion over hundreds of millions of years.

The coal seams are the compressed residue of Carboniferous forests, swamps that stood here three hundred million years ago when the continent lay near the equator. When you drive through a road cut in eastern Kentucky and see those black seams in the cliff face, you are looking at ancient sunlight, stored underground and waiting. The entire history of this state is, in one sense, the story of what people have done to get at what the ground holds.