How was the Niagara Falls formed?

The Niagara falls were created at the end of the Wisconsin glaciations about 10,000 years ago. When the ice melted, the Great Lakes drained over the Niagara Escarpment, along the Niagara River. The River 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 eroded away, leaving the harder rock unsupported. The unsupported top rocks gave way again and again creating a sharp edge for the falls. If the entire formation had been made of softer rock the Falls would have become rapids.