North Shore Anorthosite

I was impressed last week by how much more rugged the north shore of Lake Superior is than the south shore, which I’m much more familiar with. Imposing rocky cliffs rear up all over the place.

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According to a naturalist we talked to, these formations are a very old type of igneous rock called anorthosite. I’m no geologist, so beyond “really old” and “igneous” (formed by cooling magma) I can’t really tell you a whole lot about it. All I can say is that it felt decidedly odd to be looking south across Lake Superior .

4 thoughts on “North Shore Anorthosite”

  1. It shouldn’t be too surprising, since Lake Superior is on the southern edge of the Canadian Shield. Those cliffs are the “roots” (all that’s left) of what were some of the tallest and oldest mountains on Earth before they were eroded away over eons.

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