Midcontinent Rift in Lake Superior (IMAGE) Northwestern University Caption The volcanic rocks of the 1.1 billion-year-old Midcontinent Rift play a prominent role in the natural beauty of Isle Royale National Park in Lake Superior. Credit Seth Stein, Northwestern University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.