# Arkansas River GLOF



## Phil U. (Feb 7, 2009)

Thought I would share some info I learned this summer. I took a one day class through the CO. Mountain College in Leadville called "When Ice Ruled Leadville". It was taught by geologist, Dr. Vince Matthews. Awesome day. We spent an hour or two in a classroom and then all jumped in a short bus and went to several locations where we hiked while he lectured about what we were looking at relative to the glacial history of the area. Spent time up Evans Gulch above Leadville observing the upland features. Drove up the Lake Creek drainage and spent time overlooking Twin Lakes. The lakes are created/dammed by a terminal moraine and a recessional moraine. There are lateral moraines 800' above Twin Lakes. The best part,and primary reason for me being there, was our stop at the AHRA putin for the Numbers.

Let me say, I am not a geologist, just a boater with curiosity...

Pine Creek comes in at the Pine Creek rapid. Duh! Its quite a tight valley as is the Ark at that point. Its where the Ark comes closest to the granite wall on river left with the creek coming in on river right. The last glacial period was yesterday in geologic terms. So, 10 or 11,000 years ago the Pine Creek glacier had pushed across the Ark and dammed the rio as it plugged against the river left wall. It created a lake behind it that was 600' deep and 14 miles long! The head of the lake was at Malta! GLOF stands for Glacial Lake Outburst Flood. The evidence suggests that when the glacial dam failed catastrophically the lake drained in as little as 24 hours! This cycle has happened 3 times in the last 30,000 years. You can see terraces and cuts from the several floods all down through the Numbers and Fractions. There are large rocks as far down river as Salida from these events. 

One extrapolation I've made is that since the entire rio bed was deposited, arranged and rearranged by this last event, it means that the beautiful sculpting of the granite boulders that we see, usually on the downstream side, has all been done in the last 10,000 years. Maybe I'm just getting old but that is a human scale of time. 

Anyway, this all has certainly changed how I look at and experience the river. What a beautiful paradise we have to paddle in.


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## soggy_tortillas (Jul 22, 2014)

That's crazy awesome!! I love rocks, so much. I actually really wanted to be a geologist, just to lazy to go to school.

I've always been super interested in erosion... I usually end up with one or two sweet rocks in my pocket after any kind of adventure. It's just cool to think that way back when, this little tiny pebble I've got in my pocket was a boulder the size of my house!!

I usually look at my surroundings and try to think of all the processes that have worn everything down over the years, wonder what it looked like so long ago.

Thanks for the read!


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## soggy_tortillas (Jul 22, 2014)

I bet it would have been so cool to see that lake drained! Wow!!!!


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## DanOrion (Jun 8, 2004)

Say 14 mi long, average 1 mile wide, average 90 ft deep. That's 800 af (similar to Blue Mesa Reservoir). Send that all downstream in one day and you've got 400k cfs. Them's boatable flows!


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## rivervibe (Apr 24, 2007)

Thanks for the post! I love stuff like this too. I always point out to friends in my car all the glacial evidence in the Ark Valley that you see when driving north to BV. You can clearly see glacial moraines stretching across the valley in the vicinity of Nathrop and one can even imagine how the glaciers coming down from the Collegiates pushed the river up against the Mosquitoes on river left.

Indeed. Such an amazing place to live!


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## glenn (May 13, 2009)

Good stuff Phil. Thanks for the lesson.


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## benpetri (Jul 2, 2004)

GLOFs are a frequent occurrence in places where glaciers are retreating (which is almost everywhere that has glaciers these days due to climate change). Here is a video of a GLOF in Nepal. They often come in spurts as many glacial dams collapse in stages. The water is so thick with sediment it flows almost more like a viscous oil. 

https://www.youtube.com/watch?v=8ScHkS_cqk4


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## Phil U. (Feb 7, 2009)

Cool vid. I remember reading an AW article maybe 20 years ago about a river trip in Nepal that came to a confluence with a trib that was in mid GLOF. I think they were on a couple rafts and got destroyed by the volume.


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## outwash (Oct 21, 2011)

Phil
Thanks for sharing - cool stuff. Do you know if Vince matthews will be doing the class again this year? If so, I might try to take it.


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## yesimapirate (Oct 18, 2010)

*The More You Know!*

Couldn't resist.

Other Animated GIF


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## rivervibe (Apr 24, 2007)

Were the other posts in this thread taken down?


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## DanOrion (Jun 8, 2004)

Yes. Someone found my calculation of the GLOF 400k cfs obscene, which it is.


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## Blade&Shaft (May 23, 2009)

Fascinating information Phil, thanks for sharing. I remember you giving me a brief lesson on this while on the river during ELF Fest but this really explained it more thoroughly and knowing this really does change how you look at and regard the Arkansas River valley. Very cool!


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## lmyers (Jun 10, 2008)

No posts were taken down, there were 2 separate threads, one in rafting and one in kayaking. They have been combined.


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## Phil U. (Feb 7, 2009)

outwash said:


> Phil
> Thanks for sharing - cool stuff. Do you know if Vince matthews will be doing the class again this year? If so, I might try to take it.


Yeah, I think he offers it a couple times a year. At least twice last year, and it does fill up.


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## restrac2000 (Mar 6, 2008)

We backpacked in the Wrangell St Elias years ago and waited near one glacial lake for one such outburst but it never materialized in our window. I would love to see one someday and they are reliable occurrences annually on many glaciers.

Photo Gallery (U.S. National Park Service)

Cool to think about the bigger ones that shape landscapes.

Phillip


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## rivervibe (Apr 24, 2007)

lmyers said:


> No posts were taken down, there were 2 separate threads, one in rafting and one in kayaking. They have been combined.


Thanks! Don't know how I missed that.


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