2026-09-10
And that is why the region shakes more often than anywhere else in eastern Canada.
Look at a relief map of Charlevoix. Between Baie-Saint-Paul and La Malbaie, a great arc of hills surrounds Mont des Éboulements, and the St. Lawrence swallows a good part of it. That shape is no accident: it is the scar of an asteroid.
About 450 million years ago — the exact age is still debated, more on that below — an asteroid a few kilometres across struck what would become Charlevoix. Estimates of its size range from 2 to 6 kilometres. The impact fractured the rock down to about twelve kilometres deep.
Today the crater is roughly fifty kilometres across. Before hundreds of millions of years of erosion, it may have measured 70. Only part of it can be seen: the rest lies hidden under the St. Lawrence.
At its centre stands Mont des Éboulements. It is neither a volcano nor an ordinary summit: it is the crater's central peak, rock that rebounded upward right after the impact — a little like the water that springs up in the middle when you drop a stone into it.
In 1965, geologist Jehan Rondot, of Quebec's Ministry of Natural Resources, was mapping the region. At Saint-Hilarion, he noticed strange cone-shaped fractures in the rock: shatter cones.
They form when a gigantic shock wave passes through rock. Their surfaces carry horsetail-shaped striations that no other geological process can produce: the signature of an impact. His colleagues confirmed it, and Charlevoix's great half-circle changed status. It was no longer a quirk of the landscape — it was a crater.
Jehan Rondot died in 2019. His shatter cones are still there at Saint-Hilarion — but look closely: in that coarse-grained rock, they are easy to miss.
In the 1970s, the crater was thought to be about 350 million years old. In the early 2000s, estimates went back as far as 410 million. In 2019, analysis of tiny zircon crystals deformed by the shock gave 450 million years, give or take 20 million.
Today, researchers place it between 453 and 430 million years ago, near the end of the Ordovician. One thing is beyond doubt: the impact happened long before the dinosaurs, which appeared about 230 million years ago.
Charlevoix is the most active seismic zone in eastern Canada. More than 200 small earthquakes are recorded there every year — on average, one every day and a half. Most are far too weak to be felt. But the region has also known five damaging earthquakes of around magnitude 6: in 1663, 1791, 1860, 1870 and 1925.
The crater does not explain everything. Beneath the St. Lawrence run very old faults, inherited from a rift — a break in the Earth's crust much older than the impact. The asteroid came and shattered rock that was already cracked.
Researchers see a striking pattern:
In other words, the crater does not cause Charlevoix's big earthquakes. It explains why the ground trembles there so often.
The Charlevoix Geopark, part of the UNESCO Global Geoparks Network, offers sites where you can see traces of the impact, including the shatter cones of Saint-Hilarion.
How this page was made
Written by Claude, an artificial intelligence made by Anthropic, and reviewed by a human editor before publication. Every figure comes from one of the sources listed. Where they disagree — the crater's age, the asteroid's size — the article says so rather than choosing for you. Found a mistake? Report it through the Contact page: we will fix it, and say so.
