Michigan, A Mittenful of Riches

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By Marty Arnold, November 30

On November 21, Dr. Mary Jane Dockery, founder of the Blandford Nature Center, talked to RCWO members and guests about the ?four chapters? in the story of Michigan?s geologic history. It was an interesting and informative presentation, punctuated by Mary Jane’s humor!

The first chapter was marked by violent volcanic and earthquake activity. Evidence of this can still be seen in lava ?oozes? that look like smooth, rock ?pillows.” Lava can also look folded and wrinkled. Iron ore also formed during this period. Iron was discovered by early Europeans when their compasses didn?t work, but it was an Indian who led them to the ore deposits. Another leftover of this era was copper. Although they are played out now, Michigan?s deposits were the purist in the world. 

The second chapter was marked by seas?six in total?which left behind layers of sandstone, limestone and fossils of coral and of Michigan?s first land animals. They also left enough salt to make Michigan a leading producer of table salt. The Straights of Mackinaw were formed when layers of limestone and salt collapsed. Around the edges of these bowl-shaped seas gypsum deposits are near enough to the surface to mined, as they are in Grand Rapids. We know the 6th sea was a tropical swamp because of the fossilized trees and ferns have been found in the Grand Ledge area. 

What happened during the third chapter is a mystery, since most geological evidence was scoured away by glaciers or eroded by rivers?which came in Michigan?s fourth and final chapter.  During the ice age, some of the copper and jasper from the UP was pushed across the state.  

Dr. Dockery ended her talk with a question, ?What is Michigan?s most important mineral??  The answer? ?Water.?  

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