That sea shaped Canada, long before any cities appeared on the landscape.
Today, we call it The Champlain Sea.
The last ice age that existed from 80,000 to 14,000 years ago covered the landscape where cities such as Montreal, Ottawa and Toronto are now found. The ice sheet was three kilometres thick and it scraped the rock into sand and clay, while pushing down the land to below sea level due to its weight.
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 went to a depth of about 100 metres to 200 metres.
About 13,000 years ago, Mount Royal was an island within the great sea.
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.
At first, the sea was very cold due to the melting glaciers, but over time it warmed up. It was also a salt water sea, verified by the fossil shells found in the area of where the sea once was. Current estimates have it at a temperature of about 1 degree Celsius to eight degrees Celsius, with a salinity of 10 to 30 parts per thousand. For contrast, the North Atlantic is about 35.5 parts per thousand in salinity.
With the great ice sheets gone, the ground began to rebound upwards. This was a slow process, and while the sea levels were rising due to melting ice sheets, the ground was rebounding five to eight times faster than the sea level was rising.
The life of the Champlain Sea was limited from the very beginning.
As the sea retreated, it left a new landscape behind. The beaches of the sea became smooth plateaus and deep coves became cliffs.
As cities grew in the area, many roads followed the natural gradients carved by the water. About 9,500 years ago, Sherbrooke Street in Montreal was a beach. About 8,000 years ago, waves were washing up along Ontario Street.
As the water slowly disappeared, it left the soil that became the richest farmland in Quebec.
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.
In the basement of the Smith House on Mount Royal, built in 1858, there is a huge rock that runs along one wall of the 10,000 square foot house. This rock was rounded and polished by a glacier 80,000 years ago and dropped in that location where it became part of the sea.
Of course, its not all good and beneficial. The sediments from the sea also create rapid retrogressive slope failures and amplified shaking during earthquakes.
The Notre-Dame De-La-Salette slide is the deadliest Leda clay landslide in Canadian history. It occurred on April 26, 1908, destroying 16 houses and killing 35 people, including 23 children in the Ottawa area.
Within 60 kilometres of Ottawa over the past 150 years, a total of 250 landslides have occurred.
Around 4,500 years ago, humans started to arrive in the area of the Champlain Sea after it had mostly disappeared. About 500 CE, the first permanent settlement in what is now Montreal popped up.
Over in the area of Ottawa, as the sea disappeared, and the land rebounded, the Ottawa River began to form, cutting through the muddy sea floor that was created by the water. It took centuries for the new river to flow, as it followed the retreating sea all the way to Montreal. Preston Street in Ottawa became a minor channel of the river, that enlarged due to the glacial runoff. As the Ottawa River shrank, the Rideau River advanced to fill the abandoned channels.
When Colonel By arrived in the Ottawa area to create Bytown, the area of Preston Street was simply a muddy branch of the Dow Swamp.
During its existence several sea species thrived in the water.
Hundreds of fossils, mostly clamshells, have been found in the area.
Animals fossils that have been found include at least 20 beluga whale fossils, along with the bones of Harbor Seals and Ringed Seals. Among the whale fossils, five have been found in Montreal, and six were found in Ottawa.
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.
In August 1849, a farmer named George Thorp found bones poking out of the dirt along a railway line that was being built. The bone came from a large animal but not a cow or a horse. After it was analyzed, it was found to be the bones of a beluga whale. This raised the question of how whale bones reached so far inland, and the first investigation into the Champlain Sea began.
In September 1906, a farmer was digging a well in the Ottawa area when he hit a buried shell layer and then found a whale skeleton 14 feet below the surface.
In July 2001, a farmer 90 kilometres northeast of Montreal was digging a ditch when she uncovered the bones of an animal. Around the bones, she saw seashells within the clay soil. The Quebec Agriculture Department said they were the bones of a bull but a few weeks later, a paleontology crew unearthed the bones, which were those of a white whale that swam in the Champlain Sea 12,700 years ago.
They called the skeleton Felix and it is the best preserved fossil from the St. Lawrence Lowlands from 13,000 to 10,000 years ago.
There is another tale associated with the Champlain Sea. Muskrat Lake, Ontario was once part of the Champlain Sea. After the sea disappeared, the lake was left behind and in some places is 240 feet deep. Within the lake, there is said to be a sea monster named Mussy, who some say is a remnant of what was once in the Champlain Sea.
The creature was first described by Samuel de Champlain 350 years ago, but the Indigenous people describe the creature much father back. It is said that Mussy has a head like an alligator, a grasshopper-like legs and is 20 feet long.
In 2006, Canadian singer-songwriter Bruce Cockburn released the song Twilight of the Champlain Sea.
I’ll end the episode with part of that song.
https://www.youtube.com/watch?v=X4WGza5ykzw&t=67s
Information from Canadian Encyclopedia, Montreal Gazette, Wikipedia, Ottawa Citizen, Kingston Whig-Standard, University of Waterloo, New York State Museum, Earth Observatory,
