La Moinerie
Key facts
- Country
- Canada
- Diameter
- 8 km
- Age
- about 400 ± 50 million years
- Location
- 57.43° N, 66.62° W
Lac La Moinerie, a lake about 8 km across in the boreal forest and tundra of northern Quebec, with an island and scattered boulders of impact rock.
La Moinerie is an impact crater about 8 km across in northern Quebec, in Canada, occupied by Lac La Moinerie, a lake south-west of Ungava Bay.
Discovery. Like several other crater lakes in the region, La Moinerie was identified from its round shape and confirmed by rocks found nearby. Geologists found blocks of impact melt rock and breccia in glacial deposits along the shores, carried from the crater by ice sheets. Microscopic shock features in quartz and feldspar in these blocks showed that they were made by an impact.
What it hit. The impactor struck ancient crystalline rock of the Canadian Shield, mainly gneiss and granite. Glaciers have since eroded the area deeply, so the lake occupies the lower part of the original crater.
Age. Argon dating of the melt rock gives an age of about 400 million years, in the Devonian, but with a large uncertainty of about 50 million years.
Why it matters. La Moinerie adds to the long list of impact craters preserved on the Canadian Shield, a region of old, stable crust that is one of the best places on Earth to find them. The impactor is unknown.
Visiting. The lake is very remote and can be reached only by aircraft.
Did you know?
La Moinerie was confirmed from boulders of melted rock carried by glaciers.
Its age is uncertain by about 50 million years.
The lake fills the lower part of an ancient crater.