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Avalanches in southern SN

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Avalanches in southern SN

Postby johnmuir » Fri Jul 13, 2018 2:07 pm

Dear HSTers,

I am a geomorphologist (which means I get paid to look at, and ponder, landforms). One of my interests is avalanches, and the effect they have on landforms. One of the best places to study that, from a climate perspective, is the southern SN (lots of snow, not much rain). But I need more to find a good study site: the right slope steepness and the right material.So, I turn to the experts (you), with a quite broad question:
1. Have you experienced/seen avalanches in the southern SN - loosely defined as Yosemite and further south? Where was that? I'm particularly interested in terrain less steep than 45 degrees, and in 'dirty' avalanches that scrape the landscape. Photo's would be awesome.
2. What kind of material did the avalanche move over? Pure rock, or also some sand and dirt?

I'd love any and all ideas/answers/suggestions, here or as pm.



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Re: Avalanches in southern SN

Postby johnmuir » Fri Jul 13, 2018 2:14 pm

Quick addition: I'm looking for areas above treeline. Good example sites could be: the summit plateau of Mount Bradley, or slopes immeditaely south of Shepherd Pass.
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Re: Avalanches in southern SN

Postby rightstar76 » Sat Jul 14, 2018 3:07 am

Welcome to HST!

Sounds like a great job - I should have majored in that. :) Why don't you introduce yourself? Are you working on a masters or doctorate? Is this your first time in the Sierra Nevada?
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Re: Avalanches in southern SN

Postby Harlen » Sat Jul 14, 2018 3:04 pm

Johnmuir, you are without a doubt one of our greatest heroes! And in your current incarnation, you sound pretty great too. I do a fair amount of wintery ski travel throughout the range, and also have experience doing some lightweight field sampling/photo doc work for former UCSC geomorphologist extraordinaire Bob Anderson- do you know him? So I'd be happy to help out if I can. The first place I thought of, before even finishing your above query was the south-east facing slopes above Shepherd Pass. I skied down Shepherd [no-skied to Shepherd, hiked down the eastside.] in the spring of 2017, and encountered a significant (~250 meter) avalanche path. The point of initiation was ~3500 m. on the lower SE slopes of Junction Pk., ~1500m due north from the pass. The avalanche tore through a mixed talus slope (rock, gravel, sand), and finally, through the treeline scrubby forest, mainly comprised of manzanita and curl-leaf mountain mahogany. I'll see if I can dredge up a few photos John. Good luck with your studies, please post the "Abstract," and the location of any relevant papers you produce. Thanks, the Harlens.

p.s johnmuir writes:
But I need more to find a good study site: the right slope steepness and the right material. So, I turn to the experts (you), with a quite broad question:
1. Have you experienced/seen avalanches in the southern SN - loosely defined as Yosemite and further south? Where was that? I'm particularly interested in terrain less steep than 45 degrees, and in 'dirty' avalanches that scrape the landscape

Since you are looking for a study site, I will recommend the area best know for predictable "dirty avalanches"- the wide array of south-facing slopes and gullies that hang above Hwy 120 beginning about 4 miles east from Tioga Pass, and carrying on till about 4 miles before the junction with Hwy 395. These slopes all face south or SW, and are an infamous obstacle to cross-country skiers hoping to enter Tuolumne Meadows, and onward. The problem I see with this as a study site is that it is often a bloody dangerous place to be- period! There is no safe location to study this area from. But if you need a lot of data, this is your place. Just be sure you're getting "hazard pay," and that your insurance is current. All the best, Ian.
Last edited by Harlen on Sat Jul 14, 2018 4:26 pm, edited 4 times in total.
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Re: Avalanches in southern SN

Postby Harlen » Sat Jul 14, 2018 3:51 pm

Hello Again Johnmuir,

I found some photos that may be of use, though not of the avalanche slope itself:

carl book 143.JPG
The photo above is of the slopes ~200 meters above the avalanche path. I believe that this would be very similar to the substrate beneath the avalanche. The second photo (looking due north from the area just below Shepherd Pass) shows the approximate location of the upper half of the avalanche. The avalanche began above, and to the west of the tree-line seen in the distance, right of center. That is the second basin north-east from the pass- the one that runs due east from Junction Peak. Unfortunately, the actual avie path is hidden by the distance, and the gray ridge to the NW.

Hope that helps; we'll keep our eyes peeled for more. What sort of photo doc., and other sort of descriptive notes would you like John? The Harlens.
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Re: Avalanches in southern SN

Postby johnmuir » Mon Jul 16, 2018 12:31 pm

Rightstar, thank you! I'm a bit beyond my doctorate, but hope to looking for doctoral students for this topic soon (that is, I hope to obtain funding first).
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Re: Avalanches in southern SN

Postby johnmuir » Mon Jul 16, 2018 12:50 pm

Dear Harlens,

Thanks so much! Yes, I know both Andersons, they are indeed legends in the field! I really appreciate the images you sent, it gives me a much better feel for the terrain. Based on that, I've looked more in detail at Google Earth and flagged a few places that I think are good options. These places appear to have slopes that allow for initiation and stopping of an avalanche, and also appear to have material that is somewhat finer than only rock. The latter is helpful for the analyses that I hope to do. But I'm still quite uncertain of those aspects as well. What do you (and others) think, based on the attached .kmz file for Google Earth: are these places that you know have experienced avalanches, and are they indeed somewhat less coarsely textured (i.e. rocky) than other places?

I recognize that not all these places are very accessible, but I consider that a secondary problem for the moment.

Thanks so much for your insights!
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Re: Avalanches in southern SN

Postby Jimr » Mon Jul 16, 2018 5:22 pm

I guess mud slides don't count?
36.694260
-118.327088
That is where the Shepherd pass trail was wiped out by an avalanche, but I think it started as a mud slide.
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