Toronto man maps hidden shoreline of Lake Iroquois

Lake Iroquois Shoreline Photo Courtesy of Paul Smith

Cottagers are no strangers to lakes. They’re a main feature of Ontario’s cottage country, forming much of its landscape. But as it turns out, lakes have played a pivotal role in shaping city landscapes as well.

Take Toronto, for instance. Many of the city’s residents live their entire lives without realizing that some of Toronto’s most prominent geographic features were formed by a lake that existed 12,000 years ago.

Lake Iroquois was a larger, deeper version of Lake Ontario that inhabited the Toronto area before beginning to recede during the last ice age. The lake was formed by an ice sheet that damned the St. Lawrence River, forcing the water behind it to rise. The shoreline of Lake Iroquois reached much further into the city than present day Lake Ontario and would have left Toronto’s downtown core under approximately 50 metres of water.

Intrigued by the geographic anomalies left behind by Lake Iroquois, Toronto-resident Paul Smith, who lives in the south end of East York, has spent the pandemic mapping the shoreline of the ancient lake throughout the city.

Glen Edyth Drive
Photo Courtesy of Paul Smith

“The hill that Casa Loma’s on on the north side of Davenport Road and also the Scarborough Bluffs are two of the best examples,” Smith says.

Smith, a retired user experience specialist for IBM who holds a PhD in cognitive psychology, first became interested in Lake Iroquois’ shoreline while exploring his own neighbourhood. “I live at the bottom of this big hill in Toronto and I’ve always been curious about how that developed,” he says.

Aware that the sharp incline leading up to Casa Loma and the Scarborough Bluffs were remnants of Lake Iroquois’ shoreline, Smith realized that he’d never seen anyone map the shoreline between those two points. So, he took the project upon himself.

Avenue Road
Photo Courtesy of Paul Smith

Using a variety of maps, including an interactive topographic map on Natural Resources Canada’s website, and some help from retired geologist Ed Freeman, Smith was able to follow the contours of the shoreline. To ensure he didn’t forget any of his findings, he photographed each section, compiling it in a document.

Some of the areas, however, proved more difficult to find than others. “Leaside is one of them,” Smith says. “And the other one is near where I live, right around Victoria Park, south of St. Clair. It goes through there, but the signs are incredibly subtle. And then it picks up again as you get towards Scarborough.”

Smith adds that anywhere around streams or rivers is also difficult to follow. “The Rouge Valley is a complete hodgepodge,” he says. “I went up there to try and figure it out and the shoreline just disappears.”

One of the areas that surprised Smith was an east-to-west street named Old Bridle Path that runs just north of the CPR railway track, separating the neighbourhoods of Moore Park and Rosedale. “There’s a major ridge there that I didn’t know about. I’ve probably seen it over the years, but it never really registered,” he says.

MacLennan Avenue
Photo Courtesy of Paul Smith

Throughout his research, Smith also discovered that many of Toronto’s wealthiest neighbourhoods are perched on top of the cliffs formed by Lake Iroquois’ shoreline, including Casa Loma, the Beaches, Cliffcrest, and Moore Park.

The mapping process involved a lot of driving, fresh air, and a little climbing, but Smith says it’s allowed him to see the city in a whole new way. “It’s sort of like I’ve got X-ray vision and can see the shoreline everywhere I go.”

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