Signing up enhances your TCE experience with the ability to save items to your personal reading list, and access the interactive map. Photo taken on: September 28, Previous Next The Niagara Escarpment, in its Ontario portion, is km long, covering km 2 , with a maximum height of m.
An escarpment may be defined as a steep rock face of great length formed by an abrupt termination of strata. The escarpment marks part of the shore of an ancient sea centered in Michigan, which extended west from Rochester, NY, across Ontario to Michigan, then down the west side of Lake Michigan into Wisconsin.
Water erosion and glaciation molded its striking features. Water continues to shape the landscape through the rivers which flow through it and from its more than 60 waterfalls. Historically, the escarpment's waterfalls, forests and rocks provided power and building materials for a young province. Then as they melted northward for the last time, they released vast quantities of melt water into these basins. The Niagara Peninsula became free of the ice about 12, years ago.
As the ice retreated northward, its melt waters began to flow down through what became Lake Erie, the Niagara River and Lake Ontario, down to the St. Lawrence River and on to the Atlantic Ocean. There were originally five spillways from Lake Erie to Lake Ontario. Eventually, these were reduced to one, the original Niagara Falls, at the escarpment at Queenston-Lewiston. From here, the falls began its steady erosion through the bedrock. However, about 10, years ago, through an interplay of geological effects including alternating retreats and re-advances of the ice, and rebounding of the land when released from the intense pressure of the ice isostatic rebound , this process was interrupted.
The glacial melt waters were rerouted through Northern Ontario, bypassing the southern route. For the next 5, years, Lake Erie remained only half the size of today, the Niagara River was reduced to about 10 percent of its current flow, and a much-reduced falls stalled in the area of the Niagara Glen. About 5, years ago, the melt waters were once again routed through Southern Ontario, restoring the river and falls to their full power.
Then the falls reached the whirlpool. It was a brief and violent encounter: a geological moment lasting only weeks, maybe even only days. In this moment, the falls of the youthful Niagara River intersected an old riverbed, one that had been buried and sealed during the last Ice Age. The falls turned into this buried gorge, tore out the glacial debris that filled it, and scoured the old river bottom clean. It was probably not a falls at all now but a huge, churning rapids.
The falls then re-established at about the area of the Whirlpool Rapids Bridge and resumed carving its way through solid rock to its present location. Cavitation is a special type of erosion that happens at waterfalls because only at the base of waterfalls is there enough speed to produce enough bubbles close enough to rock to affect it.
This is the fastest type of erosion. As the water goes over the falls, it speeds up, loses internal pressure, air escapes as bubbles or cavities. These cavities collapse when the water comes to rest, sending out shock waves to the surrounding rock, disintegrating it.
The startling green colour of the Niagara River is a visible tribute to the erosive power of water. An estimated 60 tons of dissolved minerals are swept over Niagara Falls every minute. The Great Lakes in general are very sensitive to high-or-low precipitation years, and this can affect the flow from Lake Erie into the Niagara River, however the levels have been regulated by the International Joint Commission USA and Canada since The treaty also specifies that all water in excess of that required for domestic and sanitary purposes, navigation and the falls flow may be diverted for power generation.
The escarpment formed over millions of years through the differential erosion by weather and streams of rocks of different hardnesses. The Niagara Escarpment has a caprock of dolostone which is more resistant and overlies weaker, more easily eroded shale rocks.
Through time the soft rocks weather and erode away by the action of streams. The gradual removal of the soft rocks undercuts the resistant caprock, leaving it standing as a cliff - the escarpment. The erosional process is most readily seen at Niagara Falls, where the river has speeded the process. The Niagara Escarpment is not formed by faulting. The land that is now Southern Ontario emerged from the sea of the Paleozoic Era at least million years ago or more.
The Ordovician and the Silurian rocks of the Niagara Escarpment are of the oldest found in Niagara dating back to — million years ago.
It also continues easterly through Wisconsin and Illinois, United States.
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