* Glacial Erosion: The most significant factor was the Wisconsin glaciation, the last major glacial period that ended about 11,700 years ago. The massive ice sheet carved out the Niagara Escarpment, a steep cliff, and the Niagara Gorge. As the glaciers retreated, they left behind a vast amount of meltwater, which eroded the bedrock further, contributing to the formation of the falls.
* The Niagara River: The Niagara River, which flows over the falls, was also shaped by the glaciers. They carved out the path of the river and connected the Great Lakes to the Atlantic Ocean. The river's flow is what continues to erode the falls, causing them to recede over time.
So, while not a single event, the glacial period and subsequent erosion were the primary drivers behind the formation of Niagara Falls.
