The "Glacial Potholes" began to form after the last glacier age when the Deerfield River first started to flow over these rocks, about 14,000 years ago. The formation of these river-eroded features thanks to the great glacial lake, Lake Hitchcock, that filled the Connecticut Valley and also extended into the lower Deerfield Valley. While Shelburne Falls was not under Lake Hitchcock, it was under the sediments of the Deerfield River that built a delta into the lake. Lake Hitchcock drained by 14,000 years ago. The Deerfield River was then able to cut downward into its delta sediments. During this erosive process, which continues today, the river found itself on top of the gneiss bedrock and could start eroding holes in the hard gneiss.