Al Trippel lives in Grand Marais and Minneapolis-St. Paul, Minnesota. He grew up around rocks in the Midwest and the Western US. From a childhood hobby to a high school job, to a career in mining, and now a passion during retirement (actually it’s “refirement”), rocks continue to awe and inspire. Much of his lapidary and jewelry-making utilizes rocks and minerals found along the way. The Geology of Cook County, Minnesota – Oceans, Volcanoes, and Glaciers, Oh My! Cook County is home to a variety of rock types, some common and some extremely rare on Earth. We will look at where we sit in the regional big picture of the so-called Canadian Shield stable craton. The county straddles two rock terrains: older deep ocean greenstones and granites, and younger volcanic basalt lavas and intrusions of gabbro. Much more recently, 1-2 mile thick continental ice sheets scraped and carved the landscape into what we now see as the Sawtooth Mountains and countless inland lakes and hills. A thin veneer of glacial gravel and sand covers much of the land. Highly unusual rocks and features include: • Gunflint banded iron formation (BIF) early life forms • Sudbury asteroid impact debris layer • Mid-Continental Rift that failed • Hydrothermal (hot springs) Lake Superior Agates and Thompsonite • Glaciers of immense power scraped, sculpted, and bulldozed the landscape topography • Eagle Mountain, other high knobs, and numerous water falls are the tallest in Minnesota • Lake Superior is the largest lake on Earth, and its deepest point is 1000 ft below sea level All presentations are family-friendly and free of charge. Donations are always appreciated. Take your time driving up the Gunflint Trail National Scenic Byway!
