Geologists Confirm 25-Km Quebec Impact Crater Dated to 390 Million Years

Q: What ancient clues hidden in heavily eroded rocks finally proved this 25-kilometer Canadian crater was forged by a massive meteorite?

The decisive proof was the discovery of **shatter cones** in the ancient, heavily eroded bedrock, backed by evidence of **impact melt rock**. When Gordon Osinski’s team reached the remote Lake Marsal site in 2025, they found shatter cones at multiple outcrops. These are distinctive cone-shaped fracture patterns created only by the extreme shock pressures of a hypervelocity impact. Osinski described them as the only unequivocal impact evidence visible in the field with the naked eye. Their presence ruled out the earlier idea that the structure was volcanic or a diatreme. Researchers also reinterpreted the so-called Marsal Breccia Formation as **impact melt rock**—rock melted by the enormous heat and pressure of the strike and later cooled. That added a second major line of evidence for a meteorite origin. Together, those buried clues in the old rocks confirmed that Uhackatik, about **25 kilometers wide**, was formed by a massive meteorite impact roughly **390 million years ago**. Despite hundreds of millions of years of erosion, the crater still preserves hallmarks of a **complex impact structure**, including a central uplift and steep walls.

3 articles · Updated · spacedaily.com · Sep 22

A four-researcher team confirmed a 25-kilometre impact structure around Lake Marsal in Quebec after a 2025 field expedition, provisionally naming it Uhackatik.
Shatter cones and impact-melt rock found on site provided the decisive evidence, while lab analysis dated the strike to about 390 million years ago in the Devonian.
Joël Lapointe, an amateur astronomer, first flagged the ring in 2024 through Western University’s Impact Earth reporting channel after spotting it in satellite imagery.
At 25 kilometres across, Uhackatik would be the largest crater reported since Greenland’s 31-kilometre Hiawatha structure in 2018, though formal Meteoritical Society recognition is still pending.
The find matters because only about 200 impact craters have been confirmed on Earth, leaving each new site valuable for studying cratering processes used to interpret the Moon and Mars.