With Donald Trump threatening to rename Lake Ontario, why don't we review it's natural history? We saw this in the posting "All About The Appalachians", April 2024.
The mountains and ridges of the Appalachians were formed by a long-ago sliding tectonic collision between what is now Africa and what is now North America. The land masses were then split apart by volcanic activity along the Mid-Atlantic Ridge, which is still going on. Part of what had been Africa, the land east of the Appalachians, was left in North America.
Deflected by the Canadian Shield, to the north, the collision front shifted, over millions of years, from being primarily in a south-to-north direction to primarily a west-to-east direction. This affected the later formation of Lakes Erie and Ontario, and further north.
In the following image we can see the "curve" of the ridges of the Appalachians in the lower right and Lakes Erie and Ontario to the north.
ALL IMAGES ARE FROM GOOGLE EARTH
The "focal point" of the curve of the Appalachians is around the city of Harrisburg, in Pennsylvania. If we draw a line along the long axis of Georgian Bay, to the north of Lakes Erie and Ontario, we see that it leads directly to the focal point in the curve.
The Niagara area is at the halfway point of the line. I have named this the Humber Line, because it forms Humber Bay and Valley in Toronto as indicated by the red line in the following image.
On east-west streets, such as Bloor Street, west of downtown Toronto, the gradual drop in elevation going westward is caused by this Humber Line.
The Humber Line passes right through the Buffalo-Niagara area. It causes the Buffalo shore of Lake Erie to form a straight line along the Humber Line, which is continued on the shore of Navy Island to the north.
It shows up better on a map than in the satellite imagery. The following image shows the Humber Line as the Lake Erie shore of Buffalo, indicated by the lower red line, and the shore of Navy Island, indicated by the upper red line.
The effects of the curve in the Appalachian collision, and the resulting Humber Line, shows clearly in the shorelines of the lakes.
In the above image you can see how the northern shores of Lakes Erie and Ontario form a continuous curve, as indicated by the two red lines and the two yellow lines. The curve is interrupted by the Niagara Peninsula, indicated by the blue line. The Niagara Peninsula is formed by two parallel escarpments, the Niagara Escarpment and the much-less-visible Onondaga Escarpment.
The Niagara Escarpment extends from west of Rochester all the way to Wisconsin. It forms Green Bay in Wisconsin. The Bruce Peninsula and Manitoulin Island, which separates Georgian Bay from Lake Huron, are part of the Niagara Escarpment. This is indicated by the upper white line.
The Niagara Escarpment is about 200 million years old and was there before the Appalachian collision. The escarpment is the result of uneven erosion. The pressure from the collision pushed the escarpment northward. We can see this in the bulge of the shoreline, indicated by the lower white line, that extends from St. Catharines to Rochester.
Lake Erie is the result of a folding of the rock strata resulting from the pressure of the collision. The centerline of this fold continues inland as the valley with Mile Strip Road, in Hamburg, at the bottom as indicated by the purple line.
The long-ago collision that formed the Appalachians is actually still going on. That is why there are still occasional minor earthquakes in the Buffalo-Toronto area.
The Niagara Escarpment is very important in the geography of the area. Not only does it create the Falls, it is why there are five separate Great Lakes as well as Georgian Bay. The Great Lakes occupy a basin with the Niagara Escarpment across it. This is why there isn't just one large lake. The red dots in the following image show the Niagara Escarpment, from Green Bay to Rochester. It caused the State of Michigan to exist by hindering the movement of glacial ice.
Notice that the Niagara Escarpment looks like it might once have been the shore of a sea or lake. Ordinary limestone is calcium carbonate and is made from the bodies of microorganisms over millions of years. Exposed limestone doesn't last forever and eventually weathers away.
The Niagara Escarpment was formed by uneven erosion of limestone layers. Above the escarpment is a top layer of magnesium carbonate, which is much more resistant to erosion than the usual calcium carbonate.
There is much more in the posting "All About The Appalachians", April 2024.
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