It's now a proven fact: Rocks move "down" the North Shore. Who'da thunk it? I was pleasantly surprised to see that a student at Duluth's Woodland Middle School's big annual Science Fair took on the task of proving that rocks do, in fact, move from "up" the shore (like Grand Marais) to "down" the shore (like Duluth).
(Speaking of Grand Marais, do you suppose ace North Shore photographer Bryan Hansel authorized use of his photo in the lower right of the board??)
The student used Sparky Stensaas' great North Shore rock book to identify and label the classic North Shore rocks. Then the student used a geologic map of the North Shore to identify where the rocks came from. Then, using some mysterious calculus, the student found what direction the rocks on various beaches from Duluth to Tettegouche were from their starting spot.
The conclusion was unequivocal: North Shore beach rocks do relocate. The student even nailed some of the possible causes, listing the glacial period along with longshore currents, seiches, "and even humans."
As a well-educated grown-up, I know that glaciers were the main cause of this. And that they carried their loads from the northeast to the southwest..."down" the shore. I also know that what longshore currents there are on the shore drive rocks the same way, only very slowly. Check out the rhyolite shingle beach at Iona's Beach SNA for a classic example of this; you'll find a beach full of rhyolite cobbles just west of a pure red rhyolite cliff.
But isn't it neat that an eighth grader found out the same thing all by herself? I especially like her second conclusion:
This project is valuable in learning how the beaches of the North
Shore were made and how their content is ever-changing.
Shore were made and how their content is ever-changing.
Good job, Woodland eighth grader! Good for you and for all the rock hounds out there.
1 comment:
Excellent! I love the fact a eighth grader did this and it gives me a good feeling that there are sharp kids out there. I did stop at Iona's beach this summer. Had never done that before. I have a chunk of Rhyolite sitting right here on my desk just to keep the connection to the Northshore.
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