I have noticed that there are several inlets located at both ends of the escarpment bulge pointed out as having been created by the Niagara Escarpment during the sliding tectonic collision between what is now Africa and what is now North America, that created the long chain of ridges and mountains, known as the Appalachians..
Here is a map link: http://www.maps.google.com/ .
The escarpment bulge off the Niagara Escarpment can easily be seen on a map as the curve in the shoreline of Lake Ontario between St. Catharines and Rochester. You can see the Niagara Escarpment on the map link as a dark east-west line, if you look closely. The greatest north-south extent of the escarpment bulge is approximately at the Niagara-Orleans County line. Most of the escarpment runs parallel, and just south of, Ridge Road (Route 104).
The reason that glacial ice, drawn southward by the momentum of the earth's rotation, came from the north-northwest during the ice ages, instead of directly from the north, is the momentum of the earth's eastward rotation. Some ice collided with ice already packed up against the escarpment, and continued around it. Lake Ontario would, by this time, be emptied of water because so much of the earth's water is locked up in glaciers during the ice ages, as explained in "Sea Level During The Ice Ages".
At the eastern end of the Niagara Escarpment near Rochester, and the mass of ice packed around it, this ice continued southward. Since the stationary ice packed against the escarpment would have acted as a barrier, to route moving ice along this path, there was a heavier than usual concentration of ice that passed over the eastern extent of the stationary ice against the escarpment.
This moving ice carved away the land beneath it as it continued southward. The result is what is known today as Irondequiot Bay at Rochester, and the valley which extends southward from it.
To understand why vast sheets of ice move southward during an ice age, it is necessary to remember that an object that is large enough will be affected by the rotation of the earth. The earth, being a sphere rotating around a polar axis, is spinning faster the closer we get to the equator. This has the effect on a vast sheet of ice, that is free to move over frozen ground, of pulling it southward. There is also the eastern element due to the rotation of the earth, and the momentum that it imparts. We know that a hurricane is affected by the earth's rotation in that it is the source of the hurricane's spin. The Frisian Islands, along the North Sea coast of the Netherlands, Germany and, Denmark, are actually slowly creeping eastward due to the momentum of the earth's rotation.
When an escarpment ends, as does the Niagara Escarpment at Rochester, we should not be surprised to find a river running along it's side. Low ground near higher ground tends to collect water. The Genesee River flows from the south, where it drains the higher ground into Lake Ontario.
If we look at central New York State, with it's well-known Finger Lakes of glacial origin, we see that there is no major Finger Lake that would form a line with Irondequoit Bay. In contrast, Sodus Bay to the east appears to have been formed by the same glacial thrust that also formed Cayuga Lake to the south. This indicates that some other explanation is required for Irondequoit Bay other than a direct glacial thrust from the north.
Furthermore, Sodus Bay can be seen as aligned along more of the north-northwest to south-southeast axis that we would expect of glacial movement. This is simply because the moving ice that formed Irondequoit Bay had already had most of it's momentum broken by the collision with the ice against the escarpment. If you wonder why Sodus Bay exists, notice that it is about exactly halfway between the eastern end of the Niagara Escarpment and the Adirondack Mountains further east. These two features acted as barriers to funnel a powerful movement of glacial ice between them. This is why nothing like the Finger Lakes can be found in other areas of the earth over which glaciers moved.
Irondequoit Bay is very much a reverse of Toronto's Don Valley, on the other side of Lake Ontario. Irondequoit Bay was formed by ice moving in from the lake, while the Don Valley was formed by ice moving out into Lake Ontario.
We could say that the Genesee River is the end of the escarpment while Irondequoit Bay, somewhat to the east, marked the end of the escarpment bulge created by the ice packed up against the escarpment during the last ice age.
Irondequoit Bay, and the valley extending southward from it, would seem ideal to host a major river. While there was certainly an outflow of glacial meltwater here at the end of the last ice age, it was superseded by the Genesee River to the west. The Irondequoit Bay site had the advantage of the pre-existing inlet and valley, but the Genesee River site had not only the advantage of the nearby high ground of the escarpment channeling water to it, but also a convenient drainage route through the hills and higher ground to the south.
I find that something very interesting took place at Rochester while glacial ice was crowding into the route southward marked by Irondequoit Bay, after having deflected off of the stationary ice packed up against the Niagara Escarpment. Some of the ice then "bounced" off the ice in Irondequoit Bay, and landed on what is now the shore of the lake so that it then carved the series of ponds along this shore that we now see just to the west of downtown Rochester. These are called Long Pond, Buck Pond, Cranberry Pond and, Braddock Bay. It is very easy to see, on a map, that the directional alignment of these ponds, relative to Irondequoit Bay, fits this scenario perfectly.
There are drainage channels visible near the lake shore between Irondequoit Bay and the Genesee River. But these were formed in a way opposite from the bay and the ponds, by glacial ice melting and flowing toward the lake. There are also many drainage valleys to the south of Rochester, but these were also formed by the outflow toward the lake of water from melting glaciers to the south as the ice age ended about 12,000 years ago. To the east of Rochester, we see that the hills are aligned along with the direction of glacial movement.
As we might expect, there would be more of this "diversionary ice", as we could call it, diverted to the east of the escarpment bulge than to the west, simply because of the momentum contrinuted by the earth's eastward rotation. But the same effect can be seen at the St. Catharines end of the escarpment bulge as well.
There are three separate inlets along the Lake Ontario shore just west of St. Catharines that are actually very much like the series of ponds along the lakeshore at Rochester, and were formed in exactly the same way.
Martindale Pond, at Port Dahlousie, represents the western end of the escarpment bulge. There are two other inlets further west, Sixteen Mile Creek and Jordan Harbour. Martindale Pond is curved in it's configuration because it is actually slightly within the escarpment bulge, and the ice that carved it had to find it's way around the bulk of the pack ice against the escarpment. There is no other logical way to explain the curve.
There is no like the Genesee River at the western end of the escarpment bulge. This is because that is only the end of the escarpment bulge, and not the end of the escarpment itself, as is the eastern end. The Welland Canal is very much congruent to the Genesee River at the opposite end of the escarpment bulge but is, of course, artificially-built.
Saturday, January 21, 2012
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