Geologist to share billion-year history of St. Croix Valley’s bedrock

The story spans eons and involves three distinctive and dramatic events.




2 minute read

Via Marine Mills Folk School:

Photos by Greg Seitz/St. Croix 360

Geology of the St. Croix Valley
Instructor: Jim Miller
Date & Time: March 11 @ 6:30 pm – 8:00 pm
Class Fee: $30.00
Location: Online
Details and registration

Have you ever wondered what makes the St Croix River Valley such a dramatic and beautiful part of Minnesota? Why does the St. Croix River exist and why were we almost the “Riviera of North America” perched on the edge of an ocean?

This webinar will feature a PowerPoint presentation that illustrates and describes the story of how the St. Croix River Valley geologically evolved – a story the spans over one billion years of Earth history and involved three distinctive and dramatic events.

The story starts with an intense period of volcanic activity related to a failed attempt of North America to break apart about 1.1 billion years ago.

The next geologic event occurred about 500 million years ago when shallow tropical seas teeming with early marine life inundated the interior of North America and deposited flat-lying sedimentary rocks atop the older volcanic rocks.

The last geologic chapter is related to the repeated advance and retreat of mile-thick continental glaciers over the past two million years.

Join Jim Miller, retired professor from the University of Minnesota, for a fascinating evening of exploration and discussion. Learn about what is under your feet and all around you, in preparation for your next walk ‘round hill and dale of the St Croix River Valley!


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Geologist to share billion-year history of St. Croix Valley’s bedrock