Approximately 23,000 – 12,000 years ago the Niagara Escarpment was covered with a 2 – 3 kilometers thick sheet of ice, known as the “Wisconsin Glacier”. The retreat of the Wisconsin Glacier was the consequence of the Great Lakes surrounding Niagara Peninsula and the Niagara Falls themselves.
The glacial period occurred over 65,000 years ago and it appeared in three distinct stages. The early Wisconsin Glacier covered the entire Niagara District and most of the northern North America 65,000 years ago. This glacier remained for a period of approximately 15,000 years before it began retreat.
The middle Wisconsin Glacier progressed again over the Niagara District 40,000 years ago. It remained the same for approximately 8,000 years before it began to retreat. The late Wisconsin Glacier made another progression 20,000 years ago. It remained for approximately 8,000 years before beginning its final retreat.
The plain of the lowest beach was 122 – 153 meters (400 – 500 feet) above present Lake Ontario, formerly known as Lake Iroquois.
As the Glacier retreated, the water levels slowly lowered forming four lakes. These include:
- Glacial Lake Algonquin – (area including Lake Superior, Lake Michigan and Lake Huron)
- Glacial Lake Warren – small (Lake Erie)
- Glacial Lake Iroquois – small (Lake Ontario)
- Glacial Lake Tonawanda – area western New York
As the late Wisconsin Glacier retreated northward, it created several outlets. These outlets were later cutoff because of the rising of lands from glacial rebound, with exception to the Niagara River.
The outlets include:
- An outlet from Lake Algonquin (Lake Huron) to Lake Iroquois (Lake Ontario)
- An outlet from Lake Algonquin (Lake Huron) through Lake Nippissing to the Ottawa Valley
- An outlet from Lake Iroquois (Lake Ontario) through the Mohawk Valley (Rochester) to the Hudson River.