Saint David's Buried Gorge is an ancient pre-glacial river bed that existed 22,800 years ago on the present-day

Niagara Peninsula The Niagara Peninsula is an area of land lying between the southwestern shore of Lake Ontario and the northeastern shore of Lake Erie, in Ontario, Canada. Technically an isthmus rather than a peninsula, it stretches from the Niagara River in the ...

. The ancient Saint David's River once flowed through this area prior to the advance of the

Wisconsin glaciation The Wisconsin glaciation, also called the Wisconsin glacial episode, was the most recent glacial period of the North American ice sheet complex, peaking more than 20,000 years ago. This advance included the Cordilleran Ice Sheet, which nucleated ...

during the Last Glacial Period. When the glacier retreated 12,000 years ago, the gorge and river valley were filled in with glacial silt and rocks. Approximately 4,200 years ago, the

Niagara River The Niagara River ( ) flows north from Lake Erie to Lake Ontario, forming part of the border between Ontario, Canada, to the west, and New York, United States, to the east. The origin of the river's name is debated. Iroquoian scholar Bruce T ...

intersected the buried gorge in the course of

Niagara Falls Niagara Falls is a group of three waterfalls at the southern end of Niagara Gorge, spanning the Canada–United States border, border between the Provinces and territories of Canada, province of Ontario in Canada and the state of New York (s ...

receding toward

Lake Erie Lake Erie ( ) is the fourth-largest lake by surface area of the five Great Lakes in North America and the eleventh-largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and also has the shortest avera ...

. When the river encountered the glacial silt that filled the gorge, the river rapidly changed course to fill the ancient gorge and wash out most of the silt. This led to the formation of the Niagara Whirlpool. The Niagara River reclaimed the gorge and currently flows through part of the ancient gorge. The other part of the ancient gorge extends into

Lake Ontario Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York (state), New York. The Canada–United Sta ...

at a different point than the Niagara River. The gorge is estimated to be long, wide, and deep. In the 1950s,

Ontario Hydro Ontario Hydro, established in 1906 as the Hydro-Electric Power Commission of Ontario, was a publicly owned electricity utility in the Province of Ontario. It was formed to build transmission lines to supply municipal utilities with electricity ge ...

dug two tunnels from the upper Niagara River to supply water to the

Sir Adam Beck Hydroelectric Plant Sir Adam Beck Hydroelectric Generating Stations are two hydroelectric generating stations in Niagara Falls, Ontario, Canada. Sir Adam Beck Generating Station I, Sir Adam Beck Generating Station II and the Sir Adam Beck Pump Generating Station a ...

. These tunnels had to surface when they encountered the St. David's Gorge, as the loose silt in it was unsuitable for tunneling. In 2013, an additional tunnel, the

Niagara Tunnel Project The Niagara Tunnel Project was part of a series of major additions to the Sir Adam Beck hydroelectric generation complex in Niagara Falls, Ontario, Canada. Water delivered by the major new tunnel complements other upgrades to the Sir Adam Beck ...

, was completed. This tunnel was bored beneath the old gorge to avoid the unsuitable geology.

References

{{coord, 43.150, N, 79.098, W, display=title Former rivers Canyons and gorges of Ontario Glaciology of Canada