Champlain Sea
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The Champlain Sea was a temporary inlet of the Atlantic Ocean, created by the retreating glaciers during the close of the last ice age. The Sea once included lands in what are now the Canadian provinces of Quebec and Ontario, as well as parts of the American states of New York and Vermont.
The mass of ice from the continental ice sheets had depressed the rock beneath it over millennia, causing it to rebound once it melted. This process is known as isostatic rebound, which can be observed today in the northern Baltic Sea and Hudson Bay. While the rock was still depressed, the Saint Lawrence and Ottawa River valleys, as well as modern Lake Champlain, were below sea level and flooded once the ice no longer prevented the ocean from flowing in to the region.
The sea lasted from about 13,000 years ago to about 10,000 years ago and was continuously shrinking during that time, since the rebounding continent was slowly rising above sea level. At its peak, the sea extended inland as far south as Lake Champlain and somewhat farther west than the site of Ottawa, Ontario. The remaining glaciers fed the sea during that time, making it much more brackish than normal freshwater. It is estimated that the sea was as much as 150 meters above the level of today's Saint Lawrence and Ottawa Rivers.
Modern evidence of the sea can be seen in the form of whale fossils that have been found near the cities of Ottawa, Ontario, and Montreal, Quebec, and the existence of ancient shorelines in the former coastal regions.
