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Scrooge
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Scrooge
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PostFri Aug 10, 2012 10:17 am 
Some geologists, including J Harlen Bretz and Bruce Bjornstad, have concluded that Northrup Canyon is geologically recent, carved by the Missoula Floods during the last Ice Age, 15,000 to 20,000 years ago. I think it's more likely that Northrup Canyon was carved by Northrup Creek, over the course of a million years (or more), in the same way that dozens of other tributaries to the Columbia River carved their canyons. One thing that influenced the thinking of Bretz and Bjornstad is the fact that Northrup Creek now flows into Banks Lake, in the Grand Coulee, and the Grand certainly was cut by the Missoula Floods; it wasn't there, 20,000 years ago. Another thing may have been the odd fact that Northrup Creek appears to start from two springs at the exact head of Northrup Canyon. Perhaps the canyon and the stream are the same age?
Northrup Canyon - 'apparent' headwaters area outlined in red.
Northrup Canyon - 'apparent' headwaters area outlined in red.
It does look like the stream starts there. But, up in that scabland plateau, on the edge of the canyon, where do springs that charge a year-round stream come from? There's a geologic factor, that does date from the Missoula Floods, which may explain it.
Detail from geo quad, Banks Lake.
Detail from geo quad, Banks Lake.
Detail from geo quad, Coulee Dam.
Detail from geo quad, Coulee Dam.
If the scabland erosion weren't bad enough, there's a huge deposit of flood gravel right between the heads of Spring Canyon and Northrup Canyon, that affects streamflow still further.
Annotated map of Northrup Creek headwaters area, with Missoula Floods' gravel deposit drawn in.
Annotated map of Northrup Creek headwaters area, with Missoula Floods' gravel deposit drawn in.
Northrup Creek's two springs are right at the edge of the gravel, but that's reasonable, gravel makes a good aquifer. Then, a little to the right, Klobuschar Creek flows into the gravel and disappears. There's a comfortable gradient between the Klobuschar Creek sink and the Northrup Creek springs, so it seems almost certain that one is a continuation of the other. That's fine, for the time after the Missoula Floods, but what about before them, when there was no gravel deposit there?
Northrup Canyon and Klobuschar Creek.
Northrup Canyon and Klobuschar Creek.
I suspect that, before the last Ice Age, and before the divide between Spring Canyon and Northrup Canyon was lowered, it was just all one stream, flowing from somewhere up near the ridge of the Coulee Monocline, down to ...... wherever. smile.gif But, what happened at the downstream end of Northrup Creek is tougher. It'll be the subject of a separate essay.

Something lost behind the ranges. Lost and waiting for you....... Go and find it. Go!
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lookout bob
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lookout bob
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PostSat Aug 11, 2012 11:29 am 
Scrooge....thanks for the continuing reports on Bretz flood stuff. Interesting reads indeed. Northrup is an awesome hike and I wondered about its formation too...didn't seem part of the whole general floods picture. Keep them cards and letters comin'..... up.gif

"Altitude is its own reward" John Jerome ( from "On Mountains")
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mike
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PostSat Aug 11, 2012 12:35 pm 
Perhaps it flowed north before the flood rerouted the channel?

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Scrooge
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Scrooge
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PostSat Aug 11, 2012 2:00 pm 
Perhaps, Mike, but that would leave the problem of, "Where did the water come from to charge those springs at the head of Northrup Canyon?" Or. turning it around, wasn't it convenient to have that canyon there, just when some water turned up that needed a place to run? bricks.gif Sorry. But seriously, I think it's actually more likely the creek in Klobuschar Draw was also a tributary of Northrup Creek, rather than flowing down Spring Canyon (which it does, now).
Annotated map of the Northrup Canyon - Klobuschar Creek area.
Annotated map of the Northrup Canyon - Klobuschar Creek area.
............................................................................... Bob, thanks. agree.gif I consider myself a disciple of Bretz: I look at what's there and then try to figure out what would work, what makes sense. ...... But, they were teaching Uniformitarianism when I took geology in college. It made sense, then, and it still does, for most things.

Something lost behind the ranges. Lost and waiting for you....... Go and find it. Go!
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HitTheTrail
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PostMon Aug 13, 2012 8:21 pm 
Scrooge wrote:
But, they were teaching Uniformitarianism when I took geology in college.
Don't feel bad. Plate tectonics was not accepted by mainstream geologists until the mid1970's after the Glomar Challenger got mirror image magnetic data from spreading centers. That was after I got my undergraduate degree in geology! Good insights in the TR. Keep them coming.

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