Question

There were volcanoes in MN in the past. What caused them? What type of volcano? What type of rock was formed? How do we know?

mn is minnesota

Answer 1

• The earliest volcanoes in MN formed volcanic rocks that now underlie Minnesota and began to rise up out initially of an ancient ocean, which then formed the Superior craton.
• The volcanoes were mainly Strato-volcanoes and they were well known for pyroclastic flows and ash explosions along with erupting Rhyolitic lava.
• The volcanoes resulted in the formation of the Precambrian bedrock and the rocks that are present along Minnesota's North Shore of the Lake Superior, were also created from cooling lava. In addition to these, Bentonite clay found in the southeastern Minnesota was also formed from volcanic ash.