Yooperlites were formed through a combination of volcanic eruptions and glacial movement. They formed about a billion years ago when a spectacularly violent geologic period saw North America attempt to tear itself in two. The Midcontinental Rift formed, creating unimaginable volcanic eruptions and 360,000 cubic miles of lava – one eruption produced an ocean of lava more than 1,700 feet deep. Despite this activity, the rift ultimately failed to split North America, much of which lies beneath Lake Superior today. Near the modern shore of Lake Superior, a large body of magma hardened beneath the ground to form syenite containing Sodalite known as “glowdalites”.
