The Champlain Sea

If you got in a time machine, a flying time machine, and flew over the Montreal area 12,000 years ago, you’d see nothing but the tip of Mount Royal, because this whole region was submerged beneath an ancient sea: the Champlain Sea. So the next time you’re at the lookout on the top of Mount Royal, imagine that you’re standing on a beautiful little island looking out upon an ancient sea: an ancient sea filled with whales.

The Champlain Sea was created by the weight of the glaciers that blanketed this area during the last ice age. Think about what the weight of a two-meter-thick layer of snow and ice has done to buildings in places like Canada, Germany, and Poland. Now imagine what the immense weight of a two-KILOMETER-thick layer of ice can do to a landscape! The massive glaciers that covered eastern North America during the last ice age squashed the land beneath them severely—so much so, in fact, that when the glaciers receded about 13,000 years ago, the newly-exposed land was far below sea level. The salt waters of the Atlantic Ocean rushed in and flooded the region, creating a vast inland sea, which we anachronistically refer to as the Champlain Sea.

Land that’s been squashed by glaciers bounces back eventually. Geologists call this process isostatic rebound. It took this land we call home about 3000 years to bounce back (11,000 BCE—8,000 BCE). During this period, Montreal was home to sharks and killer whales, belugas and bowheads, and the mighty fin whale (second only to the blue whale in size); Mount Royal was a little island covered in puffins, seals, and nesting seabirds.

Although Montreal poets have always referred to Mount Royal as their city’s ancient volcano, it’s actually an ancient volcanic tube, an igneous intrusion. What’s the difference? Well, like the difference between a mountain and a hill, the distinction is to some extent arbitrary. Still, for what it’s worth, your typical volcano forms when molten lava comes up through a crack in the Earth’s crust with great force. By contrast, volcanic tubes form when the molten lava oozes out of a bunch of different cracks at once, with less force, for hundreds of millions of years.

Volcanic activity of precisely this kind is what created the chain of mountains that begins with Mount Royal and the Oka Hills, and continues south through the Eastern Townships with the following mountains: St. Bruno, St. Hilaire, St. Grégoire, Rougemont, Yamaska, Shefford, and Brome; the chain ends in southern Quebec, about 15 kilometers north of the American border, with its tallest remaining peak: Mount Mégantic. The fact that we refer to these mountains collectively as the Monteregian Hills is a testament to how incredibly old they are. They’ve been worn down by the sands of time into the rounded hills we now see. It blows my mind to think of what they’ve seen. Our moment in the sun really is just a moment. We know practically nothing about the history of this place. As Carl Sagan once said: “We are like butterflies who flutter for a day and think it is forever.”