Ausable Chasm is a sandstone gorge and tourist attraction located near the hamlet of Keeseville, New York, United States. It is directly due west of Port Kent. The Ausable River runs through it and then empties into Lake Champlain. The gorge is about two miles (3.2 km) long and is a tourist attraction in the Adirondacks region of Upstate New York. It is fed by the Rainbow Falls at its southern extreme.
Geologically, the gorge is fairly simple. The Ausable River carved a gorge a little over one mile (1.6 km) long down through the 500-million-years-old Cambrian-Period Potsdam Sandstone since the end of the Pleistocene Epoch ice age around 10,000 years ago. The headward erosion of ancestral Rainbow Falls led to its location today near the visitor’s center.
Ausable Chasm was first seen by non-Native Americans in 1765 and, since then, has been a draw to tourists in the eastern Adirondacks. The chasm has a continuous exposure of a section of the Potsdam Sandstone more than 520 feet (160 m) thick, which includes a rare, mid-Cambrian jellyfish fossil.
Some of the rock formations have been given names such as Cathedral, The Devil’s Oven, Elephant’s Head, The Flume, Sentinel Rock, and Table Rock.