What is the Niagara Escarpment?

The Niagara Escarpment is a long limestone ridge running about 725 kilometres in Ontario from the Niagara River near Queenston north and west to the Bruce Peninsula and Manitoulin Island in Lake Huron. The escarpment continues across the southern shore of Lake Michigan into Wisconsin, but the most dramatic and continuous portion is in Ontario. The escarpment was designated a UNESCO World Biosphere Reserve in February 1990, the first such designation in Ontario.

The escarpment was formed about 450 million years ago during the Ordovician period, when the Michigan Basin was an inland sea. Sediment layers (dolomite cap rock and softer underlying shale and limestone) were deposited by marine organisms. Differential erosion during and after the Pleistocene ice ages stripped the softer rock and left the hard dolomite cap as a cliff face. The escarpment rises about 90 to 200 metres above the surrounding plain. It is the only place in Ontario where significant cliff and waterfall environments exist.

The escarpment is the geological feature that creates Niagara Falls. The Niagara River drops over the dolomite cap rock at Horseshoe Falls, and the falls have eroded about 11 kilometres south from their original location at Queenston-Lewiston since the end of the Wisconsin glaciation about 12,000 years ago. Other notable waterfalls along the escarpment include Webster's Falls, Tew's Falls, and the smaller cataracts of Hamilton (the 'City of Waterfalls', with more than 100 named waterfalls), as well as Inglis Falls near Owen Sound.

The Bruce Trail follows the entire 900-kilometre length of the Ontario escarpment, from Queenston on the Niagara River to Tobermory on the Bruce Peninsula. The trail, established in 1967, is Canada's oldest and longest marked footpath. The Bruce Peninsula is the northern arm of the escarpment between Lake Huron and Georgian Bay, with Bruce Peninsula National Park protecting the tip and Fathom Five National Marine Park protecting the surrounding waters. Manitoulin Island, at the northern end of the escarpment, is the largest freshwater island in the world (2,766 square kilometres). The escarpment supports old-growth forest including ancient white cedars and rare species including the Massasauga rattlesnake (Ontario's only venomous snake) and many provincially rare plants.