The Niagara Escarpment And The Meteorite

The Niagara Escarpment is a wonder of the natural world even without the famous falls that it brought into being and for which it is named. The escarpment extends from near Rochester, New York through the Niagara area to Hamilton, Ontario. From there it turns northward, on a map you can see the Bruce Peninsula in the northern part of southern Ontario and Manitoulin Island that separates Georgian Bay from Lake Huron. From there, the escarpment curves around and forms the northern part of Michigan. It finally extends into Wisconsin and results in the peninsula to the east of Green Bay.

Here is a map link http://www.maps.google.com/

The Niagara Escarpment is known to be what natural historians and geologists call a "cuesta", a ridge formed not by any type of fault line but by uneven erosion. Limestone forms over millions of years when the bodies of microscopic living things, whose bones contain calcium, collect on the bottom of a warm, shallow body of water and are compressed into rock by later such deposits. Limestone is an excellent building material and has been used since the pyramids were made of it. One of the best places in the world to see such layers of limestone created by a long ago sea is in the Niagara Gorge.

Limestone is easily weathered over time and does not last indefinitely unless it is shielded by some harder material. The Niagara Escarpment exists because it is covered by a top layer of what is called Lockport Dolostone, named for the city near the escarpment and Niagara Falls of that name. This dolostone is a form of limestone but is exceptionally hard and resistant to erosion.

The entire area was once a shallow sea but the layers of limestone that formed from it have all weathered away except for those that were under this hard cap layer of dolostone and have thus been shielded from erosion. The escarpment as we see it today has been present for about 200 million years. The layers of strata have become tilted to the south over time so that the extent of the escarpment from Rochester to Wisconsin as described above is only the northern edge of the layer of dolostone.

The question and the object of this posting is why was regular limestone forming at the bottom of this ancient sea and suddenly, Lockport Dolostone began forming over a large and well-defined area before abruptly stopping and going back to regular limestone, which has since eroded away, leaving us the escarpment because the layer of dolostone protected the layers of ordinary limestone beneath it from erosion? The spectacular mesas and buttes in the southwestern U.S. also formed from uneven erosion but these are just single formations and nothing like the escarpment in scope.

The difference between Lockport Dolostone and ordinary limestone lies in it's chemistry. Limestone is calcium carbide, the calcium originating in the bones and shells of tiny creatures in the water. The dolostone, however, is magnesium carbonate. The calcium involved in limestone formation was replaced by magnesium and the result is a much harder and erosion-resistant layer of dolostone. This dolostone is also the reason that the falls exists as it does, the softer layers of ordinary limestone below are worn away by the falling water until the resulting overhand of dolostone breaks off suddenly.

This results in the straight drop of the waterfall instead of the sloping rapids that would exist if there were no dolostone cap layer. This also explains the curious fact that, in the Niagara Region, grapes will grow more easily below the escarpment than above it. The grapes like the calcium in the soil which is replaced by magnesium above the escarpment.

But where did this magnesium come from that replaced the calcium in the limestone forming at the bottom of the sea to form the hard layer of dolostone instead of ordinary limestone? It is easily seen on the map of the Great Lakes area that the outline of the escarpment is roughly circular in shape, centered about where Saginaw, Michigan is now located. The escarpment seems to "frame" the state of Michigan.

The most common shape of a body of water is roughly circular and limestone of any form can only be created at the bottom of a body of water so we can assume that the escarpment forms the outline of a former sea. Magnesium is a reactive element and is always found on earth in combinations such as magnesium chloride, which is found in sea salts. However, magnesium does not react with oxygen or water at ordinary temperatures. It is clear that it must have been water that spread magnesium evenly but how did such a large amount of magnesium appear so suddenly and become dissolved so evenly in water?

My answer is that it could only have been a meteorite. There is simply no other way to explain the sudden appearance of magnesium and it's disappearance when it ran out. The impact crater of this "Niagara Meteorite", as I will name it, has long since been erased by the glaciers that dug the Great Lakes and reshaped the land in much more geologically recent times. The body of water must have contracted in size before the meteor struck, this explains why the layer of dolostone was sorrounded by layers of ordinary limestone that have long since eroded away, leaving the escarpment as it is today.

The semi-circular outline of the escarpment on a map is the ghost of a long ago sea. This could possibly have been a part of a larger sea which would be why the eastern part of the escarpment departs from it's roughly circular form and extends from Hamilton to Rochester. The Great Lakes of today are almost like a photographic negative (from the days before digital cameras) of this former sea.