In search of hidden Lake Iroquois

In search of hidden Lake Iroquois

Researching the shoreline of the 12,000-year old Lake Iroquois, a larger and deeper version of present-day Lake Ontario, is no easy feat. But the pandemic gave Paul Smith some time to get out of the house and wander the historic lake’s banks through Toronto.

The naturalist, who enjoys birdwatching, started thinking about the shoreline of the old lake, especially between the Scarborough Bluffs and historic Casa Loma, a private mansion built in 1914 in midtown Toronto, now owned and preserved by the city.

“What happens to the shoreline in between there?” he asked. He didn’t have the answer, and so he went in search of clues. “It started out as just a little treasure hunt.”

Smith, 71, a retired IBM employee, grabbed his camera and note pad and started walking around neighbourhoods, looking for ridges and landmasses, signs of an old shoreline. After many visits and photographs, to ensure he had it right, he began mapping the shoreline of the old lake, known as Lake Iroquois, which shared the same basin or footprint as present-day Lake Ontario.

“I’m not a geologist, but playing one on TV,” he joked about having done a few media interviews recently on his research, which took him about two months to complete.

“I’m an amateur naturalist,” says Smith, who has a PhD in cognitive psychology. “In terms of geology, I’m as green as they come.”

But Smith admits that he’s versed in research, and finished his many walks with 90 pages of documents, and about 60 photographs on ridges and places where he believes the old shoreline once existed many centuries ago.

He’s trudged through weeds, and walked Toronto’s many valleys to find the geological clues for the banks of Lake Iroquois. He says it’s important not to confuse the Oak Ridges Moraine or the Niagara Escarpment as the edges of this prehistoric lake.

“I have photos between every two blocks or so,” says Smith, who lives in East York. “I spent between two and three hours each day walking for two months.”

Asked why he took on the task, he says: “Boredom. It was just about getting out (during the pandemic) and being safe.” Sometimes his wife would join him on his daily excursions, but often he was by himself.

Lake Iroquois is the name given to the glacial lake that existed in prehistoric times, created during the last ice age. An ice dam along the St. Lawrence caused the original lake to swell and rise about 100 feet (30 metres), gobbling up land in the process.

This old lake was fed by an earlier version of Lake Erie and what was known as Lake Algonquin, a prehistoric version of Lake Huron, that drained across Ontario and directly into Lake Iroquois without first flowing into Lake Erie.

In prehistoric times, Lake Iroquois flowed south, as well, and drained into the Hudson River — now part of the Erie Barge Canal and a route south to the Intra Coastal Waterway (ICW) for boaters — ¬†at present-day Rome, New York, located southeast of Oswego.

Scientists believe that an area called the Rome Sand Plains, located just east of Oneida Lake in upper New York, has some sand ridges that were signs for the shoreline of the ancient Lake Iroquois, after the lake swelled in size because of the ice dam.

Smith says Lake Iroquois went back to almost its original size after the ice dam broke up, and the water began flowing again out the St. Lawrence. “It was fairly dramatic when the ice dam broke up…the lake went down fairly quickly,” he says.

But the depth of the former Lake Iroquois meant large parts of present-day downtown Toronto were under many metres of water, along with densely-populated areas in Scarborough, and the Don Valley river basin almost all the way north to Don Mills.

During his research, Smith came across three other maps of the old Lake Iroquois, with each differing slightly in the alignment of the shoreline.

Some of these maps carry a stamp of the Ontario Department of Mines. The location of the historic shoreline and lake bottom would have been important as a source for gravel and sand, two important aggregates used in construction and the building of the city.

“When they were building houses in the City of Toronto, these materials were needed,” says Smith. There are a few areas of Toronto where there are few or no signs left of ridges that were part of Lake Iroquois, because of construction over the past decades.

One of these areas is Leaside, a community located mid-town near Eglinton and Bayview avenues, where bulldozers used in house construction over the decades have probably flattened geological clues to the previous shoreline, Smith says.

During his research, most of which was done online accept for his many field outings, Smith came across others interested in this ancient shoreline, including geologists. He tapped into a whole community of others interested in the history of Lake Ontario.

There are others who want to map the entire shoreline of the ancient lake, including its southern shore in the U.S., and celebrate the lake like other geological features in the province, such as the Oak Ridges Morraine, where headwaters of rivers flow south.

Once Smith finished his research, which included the use of topographical maps, he said it was important for people to see it and he began sending it around to others.

He’s debated what to do with his work, and initially thought that sending it to the archives of the Toronto public library was okay, but later worried his work would simply linger on a shelf collecting dust and no one would see it.

Smith is branching out now, and is looking forward to visiting areas to the east and west of Toronto, to find other clues to the historic lake shoreline. He took a trip to a provincial park near Belleville in mid-March for some birding, and made research stops.

The ridges of the old shoreline are evident in some areas, like near The Big Apple tourist stop in Colborne, east of Oshawa, where the banks of the old Lake Iroquois shoreline can be seen by gazing just north of Hwy. 401.

Smith says he’s been told that the old shoreline moves inland the further eastward you go, and major rivers that drain into Lake Ontario, like the Ganaraska River in Port Hope, affected the shape of the Lake Iroquois shoreline, as well, causing it to move inland.

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