Avalanches in southern SN

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johnmuir
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Avalanches in southern SN

Post by 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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johnmuir
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Re: Avalanches in southern SN

Post by 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

Post by 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

Post by 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

Post by 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

Post by 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

Post by 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

Post by 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.
If you don't want to be eaten, don't look like food.

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Re: Avalanches in southern SN

Post by johnmuir » Tue Jul 17, 2018 11:46 am

Jimr, yes, you are right - they unfortunately do not count. In fact, one of the reasons that dirty snow avalanches are so interesting from a geomorphic point of view, is that you can see them well as long as the snow has not melted away, but after that their effects are hardly visible. Colleagues believe that avalanches do a lot of 'work' on the landscape, but we're having trouble quantifying it.

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Re: Avalanches in southern SN

Post by Harlen » Tue Jul 17, 2018 6:47 pm

johnmuir the geomorphologist writes:
... 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?
Hi Johnmuir,

Re. your prospective study sites, taken North to South:

1. Young Lakes

-It's a likely area for small avalanches, and one easily checked by the HST members who ski in that area, based out of the T. Meadows Ski Hut.
- From the photo, it looks like the base material there is perhaps more rocky than you'd like. It is comprised of granite bedrock, and large boulder field talus.

2. Desolation Lake Area

-Relatively easy access from North Lake TH- 5 miles to Piute Pass, then ~3.5 miles over a flatish basin to the lake, at 11,375 elev.
-Here are a few photos from our ski trip there, in June of 2017: [*still have to find a way to present them.]

3. Coyote Ridge

-This site would have the easiest access, but it's set to the east of the main divide, and only a couple points rise above 11,000.' Are there likely to be avalanches there? Maybe in the big snow years.

4,5,6. Sites

-You said that easy access is secondary at this point, but these 3 sites are all accessed by 3 of the most heinous, i.e., long and hot, eastside trails in the range.

7. Kearsarge Peak

-We don't know about the summit of Kearsarge Pk. per se, but just south. above the easy Onion Valley TH are some very similar slopes that may fit your needs. The south-facing slopes above Gilbert Lk. in the east, up to the slopes above Big Pothole Lk. are all 30-40 degree slopes of the sort of mixed substrate you're after. Photos:
carl book 003.JPG
Above are the west-facing slopes of Independence Peak, above Onion Valley TH. Likely avie paths, but too steep for your study?
carl book 012.JPG
This a view of K.Pass from the south east. The south-east facing slopes of Mt. Gould, above Big Pothole lake.
carl book 021.JPG
View from K Pass, looking west. To the right are the south and east facing slope of Mt. Gould and Rixford. I don't believe that avalanche activity is common on either side of K.Pass.

-As for Kearsarge Pk., looking at the Google Earth images, there are nice avie runs below the funnel-shaped gullies- also facing south. They exit right above the Onion Valley car park area. Might these work, or are they too steep?

-In the same area, but across the valley, is "University Col." I descended that way from Uni. Peak, where Anderson had me collecting rock samples from "upland surfaces." I'd say there's a very good chance of "dirty" avalanches pouring down that north-east facing slope pretty frequently.

8. Mount Bradley I don't know it.

9. Near Shepherd Pass site

- Regarding that small peak seen in your Google Earth image, I've been up that with my boy, and it is just that- a very little peak. In the same area though, you would have all kinds of opportunity to find avalanches, e.g., pouring of the north and east slopes of Mount Tyndall. The east-facing slopes are mostly granite bedrock. Photos:
carl book 092.JPG
North-facing slopes of Mt Tyndall, and the peak to the west, from near Shepherd Pass.
carl book 113.JPG
Slopes on the east and south-east side of "Diamond Mesa," also from near S.Pass. Note the remnants of a slab avalanche, and a small point release slide just to the right of it.
carl book 129.JPG
East-facing slopes of Mount Tyndall, from S.Pass.

What are some other likely avalanche areas of the kind johnmuir here is after? John, Sekihiker, Wandering Daisy, and any other lurking geologists and winter climbers? John Dittli, Jimr, Gazelle, Andy, Karl, Longri, et al...?

I'll add as potential study sites the beautiful country around Magee and Convict Creeks, in the colorful metasedimentary belt; along with the fascinating geologic terrain up the Pine Creek drainage, which is also reputed to be very avalanche prone. The one winter trip we took up there, we saw a series of small slides up in the cirque under the east side of Bear Creek Spire. All came from really steep slopes, and contained little material. And finally, the slopes above Aspendell are famous for big avalanches, and would make an easy access study site, as the road to that community is plowed year-round. Some locals call the place instead: "Avalanche Dell." One big avie, rolled some of the houses off their foundations! (I think that was in the 1970's.).

johnmuir writes:
I'm particularly interested in terrain less steep than 45 degrees, and in 'dirty' avalanches that scrape the landscape

John, does this mean you are looking for full-on, climax avalanches- the ones in the spring that extend all the way down to the substrate, or are you also interested in finding any big snowy avalanche? You said that you are in part studying the way avalanches influence landforms... do your average, or even large scale snow avalanches effect that kind of influence? Sometimes the first big snow storms deposit snows which are destined to warm up and slide along the substrate, but then these will subsequently be buried under all the rest of the winter snow; does that render those avalanches useless to your study?

I can dig out some more photos from around Humphreys Basin- the Desolation Lake area. I took a look at them, and the slopes around D. Lk. look to be to gentle for much avie activity. However, the slopes of Mount Humphreys, Mt. Emerson look good; and there is a lot of good-looking stuff all the way down from Piute Pass, to beyond Loch Leven on the south side of the North Fork Creek. Easy to get to as well. Best of luck with your studies Johnmuir Ian.
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