Natural lakes are common well to the north, where the Appalachian Range was subject to geologically recent glacial activity. But the basis on which this lake—the only natural one in the southern Appalachians—exists has been the source of much speculation. Recent scientific studies indicate that an unusual combination of natural processes created the lake, which is maintained by a fissure at the bottom that provides an outlet for both sediment and water and prevents the lake from otherwise simply becoming a bog. Replenishment of the water lost depends on rain levels, and apparent washing-out of sediment from the fissured bedrock bottom is causing the unstable lake levels.