Presqu'île
Key facts
- Country
- Canada
- Diameter
- 24 km
- Age
- less than about 500 million years
- Location
- 49.72° N, 74.80° W
Little to see in the forest and lakes of central Quebec, north-west of Chibougamau, apart from outcrops of ancient rock containing shatter cones.
Presqu'île is a deeply eroded impact structure about 24 km across in the forests and lakes of central Quebec, in Canada, about 30 km north-west of the mining town of Chibougamau.
Discovery. The structure was found in the 1980s, when geologists noticed shatter cones, cone-shaped fractures that form only when a powerful shock wave passes through rock, in outcrops across an area many kilometres wide. Quartz grains with microscopic shock features have also been found. There is no crater shape at the surface.
What it hit. The impactor struck very old rocks of the Canadian Shield, mainly volcanic and intrusive rocks of the Abitibi greenstone belt, more than 2.7 billion years old. Since the impact, erosion has removed the crater rim and fill, leaving only shocked rocks from beneath the crater floor.
Age. The age is poorly known. It is usually given only as younger than about 500 million years, based on comparisons with the erosion history of the region.
Why it matters. Presqu'île shows how a large impact can be recognised long after the crater has gone, from the shock features left in the rocks beneath it. The impactor is unknown.
Visiting. The area is remote forest reached by logging roads. Respect any mining claims and ask permission where needed.
Did you know?
Presqu'île was found from shatter cones scattered over a wide area.
No crater shape survives at the surface.
The rocks it struck are more than 2.7 billion years old.