A day at the beach: back to the Silurian for Easter

Geology professor Nick Eyles took a motorcycle tour over Easter Weekend, riding to the Bruce Peninsula where you can revisit the Silurian when Ontario straddled the Equator 400 million years ago

Earth Day was on April 22 so I decided to celebrate (a bit late) Easter Sunday by going back in time many millions of years. It’s been a wet cold spring in Ontario and we of the motorcycle faith haven’t had much opportunity to worship. It was a crisp day with the promise of no rain. So, I thought let’s suit up and ride north up to the tropics and spend a day on the beach. That’s right…on the beach.

By riding northwards up to the Bruce Peninsula (the big piece of the Escarpment jutting out into Lake Huron), we can revisit the Silurian when Ontario straddled the Equator 400 million years ago and much of our province lay submerged under the warm waters of a huge tropical sea.  A wonderful place; large hump backed islands of old dark coloured Shield rocks jutting out of a turquoise ocean teeming with marine life, so much so that the rocks left behind are dominated by fossils. No fish (they were to emerge later) but lots of trilobites, giant squids, corals galore, mollusks of many types and sea lilies (crinoids) whose segmented stems broke apart during major tropical storms to scatter small rounded pieces everywhere.  The remains of these organisms now form limestones which once blanketed much of Ontario but have been slowly stripped off from the north to expose the Shield below. The Niagara Escarpment is the edge of one harder sheet of limestone that is slowly being trimmed back.

Hoggs Falls

I rode up past Hoggs Falls an old favorite of mine near Flesherton where the Boyne River drops precipitously over the edge of the Escarpment down into the canyon-like Beaver Valley.  Back in 1832 someone found pyrite here (yellowy sulfur-rich iron pyrite named ‘fool’s gold’) and they did indeed rush in. It must have been quite a party until the bills had to be paid.

But that wasn’t the point of my trip. From Flesherton west to Owen Sound and then north along the Bruce, the landscape may have been recently glaciated and now covered with glacial dirt left by an ice sheet but the old Silurian sea floor isn’t completely obscured. Take virtually any highway north and there’s a strange rhythm at work by the side of the road. The landscape is corrugated like cardboard with white rock knobs sticking up every 500m or so, just like boney ribs poking out of the glacial dirt. These knobs are ‘bioherms’ a fancy word for ridge-like reefs that paralleled the shores of the Silurian sea.  Mostly made of fossil debris swept into piles by big storms these long reefs hosted vibrantly coloured colonies of marine organisms thriving in the warm clear tropical waters.  A warming thought on a cool Easter Sunday.

An odd juxtaposition you’ll agree. Tropical reef rocks with glacial stuff on top, a testament to the long northward journey of the North American plate.  I rode away from the reefs wondering to myself what this part of the world will look like in another 400 million years and where might it be?

Nick Eyles


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The University of Toronto Scarborough (UTSC) is home to a community of active learners drawn from all over the globe, determined to use what we discover – through investigation, collaboration and experience – to make our world a better place. Our campus is an integral component of Canada’s leading research-intensive university, a place where faculty contribute to cutting-edge knowledge, where the finest students are taught by the finest professors. Upon graduation, our students have earned one of the most rigorous and respected post-secondary degrees in the world. At UTSC, we are working together to find answers to tomorrow’s most important questions. And because the search for knowledge must always be conducted in a meaningful way, our campus is continually alive with innovative programming, engaging discourse and dynamic experiences that feed our spirits and enrich our minds. This is how to prepare students for the best possible future. This is how our scholarship contributes to a better world. This is our promise. Because tomorrow is created here.
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