I'm not sure how I got on this train of thought, but I found myself thinking about the geology of Illinois. Most of the state is a huge syncline, which is to say a big bowl, full of dirt.
The northern part of the state, around Chicago and across to Rockford, is glacial moraine (no real surprise, since northern Illinois marks the southernmost reach of the glaciers in mid-America, as witness the southern shore of Lake Michigan, which, along with the other Great Lakes, was formed by glaciers), while in the far south, you can, if you look at the right places, see the folding and distortion that is the result of the mountain building that created the Appalachians, some 300 million years ago (although some sources place that even as beginning 480 mya -- but that may depend on what part of the Appalachians you're talking about), when what is now North America collided with Gondwana (present-day Africa and South America).
And yes, the effects of that collision are visible in southern Illinois, hundreds of miles to the west.
And do check out the link -- it's kind of long, but very interesting, and pretty much tells the whole story, starting about 750 million years ago.
This helps in visualizing the whole thing:
And this is the sort of thing I think about when I allow my mind to wander.
The northern part of the state, around Chicago and across to Rockford, is glacial moraine (no real surprise, since northern Illinois marks the southernmost reach of the glaciers in mid-America, as witness the southern shore of Lake Michigan, which, along with the other Great Lakes, was formed by glaciers), while in the far south, you can, if you look at the right places, see the folding and distortion that is the result of the mountain building that created the Appalachians, some 300 million years ago (although some sources place that even as beginning 480 mya -- but that may depend on what part of the Appalachians you're talking about), when what is now North America collided with Gondwana (present-day Africa and South America).
And yes, the effects of that collision are visible in southern Illinois, hundreds of miles to the west.
And do check out the link -- it's kind of long, but very interesting, and pretty much tells the whole story, starting about 750 million years ago.
This helps in visualizing the whole thing:
And this is the sort of thing I think about when I allow my mind to wander.
No comments:
Post a Comment