Coppermine River Group
Coppermine River Group is a huge set of ancient flood basalts in the Canadian Arctic, spanning parts of the Northwest Territories and Nunavut. It is part of the Mackenzie Large Igneous Province and is one of the largest flood-basalt regions on Earth, containing about 650,000 cubic kilometers of rock.
The rocks formed about 1.27 billion years ago when enormous amounts of basalt lava spread over a large area of the northwestern Canadian Shield. The lava flows are very thick, ranging from 2,000 to 3,500 meters, and include around 150 individual flows, each about 10–25 meters thick. Almost all eruptions occurred above ground, with the lowest layers showing some interaction with water.
Eruptions near the Coppermine River built a large volcanic plateau about 1.2 billion years ago, covering roughly 170,000 square kilometers and containing at least 500,000 cubic kilometers of lava. These flood basalts are thought to be the same age as the Mackenzie dike swarm and the Muskox intrusion.
This page was last edited on 3 February 2026, at 07:19 (CET).