The Cincinnati Anticline

There's a natural formation known (primarily to geologists) as the Cincinnati Anticline. It's a vast oval-shaped area that extends over the three-way intersection of Ohio, Kentucky and Indiana, and extending well into central Kentucky. The oval's Eastern side runs along Cincinnati, hence the name.

According to the book Elements of Geology by William Harmon Norton, the anticline is of great interest to those studying the fossil record. The anticline is almost entirely composed of Ordovician strata, and the Silurian and Devonian decrease as they approach it. Norton takes this to mean that the anticline is "an island upwarped from the sea at the close of the Ordovician or shortly thereafter."

Supposedly it's this anticline that makes much of Kentucky so rich in fossils from the ancient ocean, including the Falls of the Ohio along Louisville's riverside - and yet the Falls of the Ohio is said to be of Devonian origin, not Ordovician. I leave the matter for professional geologists to sort out.

According to a surprisingly florid bit of text in the usually dry Kentucky Encyclopedia, the anticline is also indirectly responsible for Kentucky being the thoroughbred horse capitol of the world. Early settlers noticed the geological qualities of the anticline contributed to making Kentucky a land with densely fertile soil, rich in calcium and phosphorus, and this in turn led to it being prized by horse ranchers:

"This legacy of phosphatic limestone, inherited from millions of shells and skeletons, deposited millions of years earlier when central Kentucky was an ocean bed, was now to be used to build the skeletons of horses... the phosphatic limestone which forms the basis of central Kentucky's soil has proved its efficacy."

The anticline also just happens to roughly correspond to the area affected by the 1895 Charleston, Missouri, earthquake along the New Madrid Fault (see area indicated in red in the image above).