The Champlain Sea

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Today, I launch a new series of history episodes called Penny Size History, where I do quick dives into a historical topic.
Canada is known for many large bodies of water. Great Slave Lake, Lake Winnipeg and, of course, the Great Lakes. There was one lake though, that was so large, it was called a sea. While portions of it still exists, the sea itself is long gone.
Today, we call it The Champlain Sea.
As glaciers retreated during the last ice age, this temporary inlet of the Atlantic Ocean was created thanks to the large depression in the land created by the weight of the glaciers. Covering a vast area, the future city sites of Ottawa, Montreal, Quebec City and Saguenay were all under water, along with other portions of Quebec, Ontario, and the states of New York and Vermont. In all, it covered an estimated 55,000 square kilometres and was somewhat salty.
Lasting for 3,000 years the sea existed from about 11,000 BCE to 8,000 BCE.  The sea was at its largest at the beginning of its existence, and shrunk continually as the area began to rise above sea level over time. During its largest extent, the sea was about 500 feet above the level of the current Saint Lawrence and Ottawa Rivers. Early on, it was a cold sea but as time went on it began to warm up.
The sea also left huge swaths of clay, which would one day create large wetlands and forest types. The deposits left by the sea preserve the record of the deglacial event and have had an impact on our modern society. Today, those deposits that formed the Champlain Sea are farmed, mined for aggregate and used as a substrate for waste disposal. Buried eskers from the sea also provide potable groundwater. Of course, its not all good and beneficial. The sediments from the sea also create rapid retrogressive slope failures and amplified shaking during earthquakes.
During its existence several sea species thrived in the water. Over time, there has been the discovery of many whale fossils, including those of belugas, fin whales and bowhead whales. White whales were the most common large mammal living in the sea, feeding on fish and shellfish. With the abundance of white whales, this means there were large populations of fish in the sea including cod, eelpout, spoonheads and long-nosed suckers. It is also believed based on fossils that humpback whales frequented the sea as well.
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