Side A: The knolls and ridges found in this vicinity were formed by deposits of gravel left by the retreating glacier which covered much of Ohio during the Pleistocene Era 10,000 years ago. Popularly known as “Devil’s Backbones,” these ridges can be several miles in length. As the glacier retreated it also left large round depressions in the earth’s surface known as kettlers. A kettle was formed by the melting of a buried mass of ice.