This waterfall is a short ways off the Alpha Trail. My daughter and I were quite surprised when we came across it while hiking. After a little research:
Alpha Falls, also known as Gardiner Falls, is the mouth of the valley leading from Alpha Pass. The falls most likely formed after lake drainage through Alpha Pass was complete. Later lake drainage eroded the main gorge to its present level, leaving the valley above the falls "hanging" along the gorge wall. Many waterfalls along the walls of the gorge are at the mouths of similar "hanging valleys."This photo was taken in McConnells Mill on June 28, 2009.
Almost none of the Homewood Sandstone has been eroded at the top of the falls, suggesting that the valley has never had much flow since glacial lake drainage ceased.
Source, Pennsylvania Department of Conservation and Natural Resources Web Site. July 23, 2009.