Calamus Swamp is the only naturally vegetated and undisturbed kettle lake known to survive in central Ohio today. Glacial kettle lakes are remnants of the Wisconsinan glacier that shaped Ohio’s landscape some 12,000 years ago. They were formed when massive blocks of ice fell away from the thawing glacier and created depressions of varying sizes and shapes in the soft, wet earth. As the blocks melted, the kettle depressions filled with clear water, forming open lakes that dotted the Ohio landscape primarily in the west central, northeast and northwest regions of the state. Unfortunately, most have met a harsh fate. Over time, most have filled in with dead plant material and disappeared altogether, victims of the relentless process of ecological succession. The aquatic vegetation in Stage’s Pond State Nature Preserve, another glacial kettle lake located in Pickaway County, has been almost completely destroyed by excessive sedimentation and fertilizer runoff from neighboring farms. That leaves Calamus Swamp as a most extraordinary relict of central Ohio’s glacial past.