How did Niagara Falls form?
The Niagara Falls were created at the end of the Wisconsin glaciation about 10,000 years ago. When the ice melted, the Great Lakes drained over the Niagara Escarpment by way of the Niagara River. The River initially cut a gorge through the escarpment. The layers of rock in the escarpment have a top rock formation that is composed of harder stone that eroded more slowly than the underlying materials. The softer rock preferentially eroded away, undercutting the harder rock. The unsupported top rocks gave way from time to time creating a sharp edge for the falls. If the entire formation had been softer rock the present Falls would have been reduced to a series of rapids.
