Summary
Fieldwork at Quebec’s Uhackatik structure found shatter cones that support an impact origin for a 25-kilometre feature. Rock samples indicate it likely formed about 390 million years ago.
An amateur astronomer’s observation of a circular feature on online satellite maps led researchers to a large impact structure in Quebec. Fieldwork at the site found shatter cones—distinctive fractures associated with the intense shock of an impact—supporting the research team’s conclusion that the 25-kilometre-wide structure is an ancient crater. Rock samples indicate it likely formed about 390 million years ago.
The structure, near Lake Marsal in the remote Côte-Nord region, is named Uhackatik. The research team considers its impact origin essentially confirmed; formal recognition by a Meteoritical Society committee is expected at a future meeting.
From map pattern to field evidence
Joël Lapointe noticed the circular feature in 2024 while planning a camping trip. He contacted researchers, and a team of French scientists subsequently presented the lake area as a possible impact structure at a Meteoritical Society meeting that year. The site had previously been mapped as a possible volcanic feature called a diatreme, formed by explosive eruptions.
Planetary geologist Gordon Osinski and colleagues travelled to the site in October 2025. They found shatter cones in rock outcrops by the second day. These cone-shaped fracture patterns are a field sign of the extreme pressures produced by an impact. The team also identified a complex structure spanning 25 kilometres, with a central uplift and tall cliffs marked by columnar jointing.
The field evidence was important because a circular outline alone can suggest a crater but cannot establish its origin. Shatter cones gave the researchers a more direct geological clue that the feature formed in an impact rather than through volcanic activity.
A large and ancient structure
The estimated age comes from rock samples: the structure likely formed about 390 million years ago. Uhackatik is the largest impact crater discovered since the 31-kilometre Hiawatha structure was found in 2018, according to NASA Earth Observatory.
The discovery also illustrates how satellite maps can help guide field research. Lapointe’s observation pointed scientists towards a feature that earlier geological mapping had interpreted differently; direct examination of the rocks then changed that interpretation. The site’s remote, difficult terrain made that fieldwork challenging, but it provided evidence that imagery alone could not.
After consulting the Innu Council of Ekuanitshit, the research team chose the name Uhackatik. The site adds to the record of known terrestrial impact structures and to evidence that some large scars on Earth can remain unidentified for a long time.