As the Wisconsin Glacier retreated, the upper Lakes began draining into the lower lakes at across the Niagara Escarpment. Later on the Niagara River ultimately became the main water outlet over the Niagara Escarpment. The waters of a much larger Lake Erie began to flow over the escarpment into a larger Lake Iroquois, present day Lake Ontario.
The Niagara River began to flow from the Lake Erie basin through Lake Tonawanda and down what is now the present path of the river to the escarpment.
At this time, the lake plain from Queenston to Niagara-on-the-Lake was covered with the waters of Lake Iroquois (Lake Ontario). The height of the lake was within 11 meters (35 feet) of the average level of the Niagara Escarpment at Queenston, Ontario. This was the initial Niagara Falls. The water would flow over the Niagara Escarpment at Queenston 11 meters down to the waters of Lake Iroquois. Over time the water that flowed over the escarpment began to erode the glacial material and limestone rock, which ultimately lead to the creation on the Niagara Gorge.
The site of the birth of Niagara Falls was discovered by a geologist named Doctor Roy Spencer; today the site is known as “Roy Terrace”.
The original flow rate of water was only twenty-five percent of the present flow rate of the falls. Scientists have calculated that the volume of water flowing over the Falls was initially 37,500 cubic feet per second.
The rising of the northern crust of the earth, which was a reflex action to the weight of a Glacier at least half a mile thick, directly caused a faster outpouring of Lake Iroquois (Lake Ontario). The 11.2 kilometer (7 mile) lower stretch of the Niagara River to Lake Ontario was once 19 kilometers (12 miles) long.
Scientists have suggested that the eastern part of the North American continent is still in the process of tilting as part of the glacial reflex action. As the crust of the earth raises along the eastern seaboard the water flowing from the Great Lakes system will become slower.