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.