(From the digest):
I expect that's not possible.Today's Topics:7. Restoring the Mississippi River in Minneapolis (Dave Stack) --__--__-- Message: 7 From: "Dave Stack" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Date: Tue, 22 Oct 2002 20:49:05 -0500 Subject: [Mpls] Restoring the Mississippi River in Minneapolis I wonder if the falls could be restored, or if construction projects have mangled it beyond recognition of its original appearance?
It's not the construction projects that have been the most damaging (although that tunnel under the river that collapsed was a Real Problem). The problem with "restoring" St. Anthony Falls is that the falls are created from a limestone cap over a layer of sandstone. The water erodes the softer sandstone, and the limestone cap, unsupported, breaks off. St. Anthony Falls thus retreats upstream, and has been doing so for 1,000s of years. The limestone cap gets increasingly thin as it is followed upstream. Shortly upstream of the place of the current St. Anthony Falls, the limestone peters out and disappears. Without that, St. Anthony Falls becomes a ripple in the river.
The apron that is the current falls is protecting the remaining limestone.
Karen Cooper, in Tangletown most of the time, but in Switzerland as I write or else I'd provide more data on this; I have several books on the topic
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