I left Niagara Falls without knowing much of how it was formed, so I did my own research and learned some very interesting things:
Niagara Falls was formed around 11,000 years ago when the receding glaciers carved out the great lakes.
The melt water began to flow over the Niagara Escarpment which is a wonder in itself. It is a long cliff that extends 1,000 miles from east-central Wisconsin to Upstate New York. It forms the northern boundary of Lake Michigan and Huron and Southern boundary to Lake Ontario. It has existed for 400 million years and is believed to be the edge of an ancient basin, the Michigan Basin.
When the glaciers retreated the escarpment was exposed and the melting water water began to flow over its edge. The water eroded the softer rock at the base of the escarpment wearing it away until the harder rock at the top of the cliff caves away. This keeps the flowing water flowing in a vertical fashion (a falls) rather than eroding into a cascade as the falls carved its way southward along the Niagara River. Over the 11,000 years that falls existed it carved the basin, moving it 6.8 miles southward from its original location at Lewiston, New York.
If you do the math that comes to and average of about 3 feet 4 inches per year, however while the water was flowing the erosion was probably greater. You see, after the falls was formed, for a few thousand years there was a time that it ceased to exist.
There is evidence that 8,000 years ago the water levels of the Great Lakes were lower by about 40 to 50 meters. During that time Niagara Falls would have dried up until the water levels rose again.
At the bottom of Lake Huron in the Bruce Peninsula there are the remnants of many waterfalls, many of these falls were greater than Niagara Falls, that used to exist during the time when the water levels were low.
Today the erosion caused by the Falls is greatly reduced by human intervention, mainly channeling about 75% of the water for hydroelectric power production.
Information for this article was gather from the following sources: