Prehistoric Toronto: The Terrain of Our City Through the Ages

What was happening here hundred of millions of years ago?

By Daniel Sellers • Illustrations by Chloe Cushman

For the past few weeks, we’ve been looking at the land that makes up Toronto—specifically, at what was happening here before human habitation. We moved through geologic time periods, tracing the effects of rock formations and ice ages, and explored the fossil record to learn about the creatures big (sometimes very big) and small that lived here millions of years before we did. Here is the complete series.

The Early Paleozoic Era 450 million years ago; late Ordovician Period A golden age for the humble, unassuming invertebrate known as the trilobite.

The Missing Rock Record 450 to 3 million years ago; mid- to late-Paleozoic, Mesozoic, and most of the Cenozoic eras During which time the dinosaurs rose and fell, and were succeeded by mammals.

The Ice Age 2.5 million to 12,000 years ago; Pleistocene Epoch A time of massive glaciers and giant mammals.

Glacial Lake Iroquois 12,000 years ago; late Pleistocene Epoch When glacial meltwater pooled, for a time, over much of what is now Toronto.

The Torontoceros 11,000 years ago; latest Pleistocene and earliest Holocene epochs When post-glacial forests grew here, and humans began, gradually, to arrive.