Geology of the Escarpment

The Niagara Escarpment is recognized as one of the world's unique natural wonders. Essentially, it is a landform -- a ridge of rock several hundred metres high in some locations -- stretching 725 kilometres (450 miles) from Queenston on the Niagara River to Tobermory at the tip of the Bruce Peninsula. Today, in Ontario, the Escarpment contains more than 100 sites of geological significance including some of the best exposures of rocks and fossils of the Silurian and Ordovician Periods (405 to 500 million years old) to be found anywhere in the world.

The Niagara Escarpment has origins dating back into geological history some 430 to 450 million years, a time when the area lay under a shallow warm sea. This sea lay in a depression of the earth's crust, the centre of which is now the State of Michigan. Now geologically known as the Michigan Basin, the outer rim of this massive saucer-shaped feature governs the location of the Niagara Escarpment. In the shape of a gigantic horseshoe the Escarpment can be traced from near Rochester, New York, south of Lake Ontario to Hamilton, north to Tobermory on the Bruce Peninsula, beneath the waters of Lake Huron to appear again on Manitoulin Island, across northern Michigan and down the west side of Lake Michigan into the State of Wisconsin.

As occurs with present day water bodies such as Hudson Bay or the Gulf of Mexico, rivers flowing into this ancient sea carried sand, silt and clay to be deposited as thick layers of sediment. At the same time lime-rich organic material from the abundant sea life was also accumulating. Over millions of years these materials became compressed into massive layers of sedimentary rocks and ancient reef structures now visible along the Escarpment. Some rock layers now consist of soft shales and sandstones while others are made up of dolostone (a rock similar to limestone which contains magnesium and is more durable).

Today, fossil remains illustrating the various life forms can be found in many of the rocks as they are slowly exposed by the action of wind, water and ice.