Wisconsin Glacier in Niagara
The Niagara Escarpment was covered with a sheet of ice 2 – 3 kilometers thick (Wisconsin Glacier) 23,000 – 12,000 years ago.
The last glacial ice age occurred during three distinct periods of time during the past 65,000 years. The glacier originated east of Hudson Bay in northern Quebec and Labrador. This great glacier was known as “the Wisconsin Glacier”.
The early Wisconsin Glacier covered the 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 retreating 50,000 years ago.
The middle Wisconsin Glacier advanced again over the Niagara District 40,000 years ago. It remained for approximately 8,000 years before retreating 32,000 years ago.
The late Wisconsin Glacier advanced again 20,000 years ago. It remained for approximately 8,000 years before beginning its final retreat 12,000 years ago.
The plain of the lowest beach was 122 – 153 meters (400 – 500 feet) above present Lake Ontario (Lake Iroquois).
As the Glacier retreated, the water levels slowly lowered forming four lakes:
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
Glaciers ranged up to 4.8 kilometers (3 miles) thick. Ice at 1.2 kilometers (1 mile) thick would exert a pressure of 150 tons per square foot. It is estimated that the weight of the glacier depressed the earth 61 meters ( 200 feet). When the glacier retreated the land began to rise in what is referred to as glacial rebound.
As the late Wisconsin Glacier retreated northward, it created several outlets:
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
The rising of the lands from glacier rebound finally cut off these outlets with the exception of the Niagara River.
During the period of glaciations and shortly afterwards, the climate in Niagara was arctic. Vegetation was tundra and arctic fauna.
Glacial Lake Iroquois
Lake Iroquois (Lake Ontario) was nearly the same depth as Lake Warren (Lake Erie). Following the retreat of the middle Wisconsin Glacier and ancient lake which occupied the present Lake Ontario basin was created. This Lake was called Lake Lundy. After the waters of Lake Lundy fell due to the reflex action of the land, it became a smaller lake named Lake Iroquois.