Noteworthy gorges in Grafton Notch include Screw Auger Falls, Mother Walker Falls and Moose Cave. Screw Auger Falls is located within a steep gorge along the Bear River; when water levels are low enough, erratics are visible in the stream. Steep cliff faces and flat valley floor seen from Mother Walker Falls are characteristic of glacial erosion. However, responsibility for gorge formation is debated; they may have formed while the ice sheet retreated north of the region and contributed a large quantity of meltwater, or more likely, they formed while the ice sheet covered the area and the subglacial water was under very high pressure. Whether a particular landform was created by local glacier or continental ice sheet is also still debated. Many pegmatite vein intrusions are visible around the water-eroded bedrock of the gorges.