Analyzing a slide after the fact?

[MOHSHSIHd]

So, on the way to Vail Pass driving from the vail side yesterday you could see evidence of a skier triggered slide above the black lakes area. People who know vail pass will know it as the "rollover that slides constantly all winter". Anyway, later in the day around 12 we saw what looked like a group of people digging a pit on the same slope, even with the crown/starting point only about 20 feet skiers left of the edge of where the slab broke.

Anyway, is it just me or does this seem like a really bad idea? "Lets see, one skier triggered the slide, so lets get 6-8 people up on the face and lets all get in a pit."


Im going to assume that the chances of the rest of the face sliding are increased after half of it has slid and thus some of the "integrity" of the slope that was holding it up in the first place is gone?


would like to here what you guys think...

[powderfarmer]

I would call it dangerous... yes..... However, I have read many times, that with slab avy's once the majority of it has gone, all the tension is gone, there is no energy left in the pack and therefore safe. Hangfire is a different storey, as it has no support left, and just needs a small trigger. Just the way I think about it.

[dbp]

I would call it dangerous... yes..... However, I have read many times, that with slab avy's once the majority of it has gone, all the tension is gone, there is no energy left in the pack and therefore safe. Hangfire is a different storey, as it has no support left, and just needs a small trigger. Just the way I think about it.

I was about to type basically the same thing. It seems like this is the whole point of control work with explosives.

[MOHSHSIHd]

I would call it dangerous... yes..... However, I have read many times, that with slab avy's once the majority of it has gone, all the tension is gone, there is no energy left in the pack and therefore safe. Hangfire is a different storey, as it has no support left, and just needs a small trigger. Just the way I think about it.

Well, I would say less than half the face went. From one side to the other the slope's shape, angle, and aspect is uniform. So, we were trying to figure out why the crown just didn't keep going all the way across, but the lack of energy that you point out could be the solution.

[LeeLau]

Doesn't sound like they were on the bed surface then digging their pit? Personally, if a slope with a particular aspect slides I take that as one sign that other slopes or other portions of that slope could also slide.

I'm not experienced in Rockies snowpack but I'd also take it a possible sign that whatever bonds between layers that was weak enough to let go is present between one part of the slope that slid and the other part of the slope that didn't slide.

Not going to make judgments about the party that dug the pit since I wasn't there myself

[Orange Julius]

Setting the danger debate aside for a second, it can be a real learning experience to dig a pit right near a slide to see how your stability tests respond to an interface that is known to be unstable. It can help calibrate your pit analysis a bit.

[Max Gosey]

The title of this thread sparked a thought that I read about in Tremper's book: "digging around on the flanks of a slide path shortly after it has slid is a great way to look at the weak layer and the causes of the slide. Firsthand experience" because he claims that once the slope has slid, it's much more stable.

I would say digging around ON the bed surface wouldn't be so bad (please correct me if this sounds absurd), but I would say poking around on a slope of similar elevation and aspect as that that slid a short time ago (but this slope hasn't slid yet) would be unsafe and a very bad idea.

And phish, I think 20 feet of width of existing snowpack still provides about the same amount of lateral support as would the whole slope, but I could be wrong about that.


This brings up a more general question though: what decides exactly (other than the stiffness of the slab) where a propogation of a fracture stops? I've kinda wondered why the flanks of a slab are where they are and not five feet further out or further towards the center of the slab...

[Toby]

This brings up a more general question though: what decides exactly (other than the stiffness of the slab) where a propogation of a fracture stops? I've kinda wondered why the flanks of a slab are where they are and not five feet further out or further towards the center of the slab...

I can think of about 20 things off the top of my head.

[Foggy_Goggles]

Sounds like a bad idea. One of the best indicators of hazard is fresh slides on similar aspects. Analyzing slides one the bed surface after the fact is a different deal.

[phatfreeheeler]

I'm moday morning quarterbacking, but here's my view.

Seems like an unnecessary risk to go out onto a similar aspect, elevation, steepness, and snowpack, as an obvious recent slide, assuming the slope is substantial. That goes against the first rule of avalanche awareness, pay attention to what has already slid.

Personally, I like to look at snowpacks that have just slid because I'm a dork and find that stuff interesting. I would have skied off the top of the crown, sidestepped up, and cut into the crown to get a clean pit. This is what every avy control person I've ever worked with would do. The only time I wouldn't do this is if there is still a substantial slope still above the crown.

But hey, I wasn't there, so maybe their risk wasn't as great as you made it out to be.

[MOHSHSIHd]

good point, but in CO I feel like anything can happen....


My friends give me shit for being too safe sometimes....

"too safe"?

hell, i like being alive....


I like to get a feel for the snowpack.....I like to ski the first run with many options for safe zones


I am finally taking my avy 1 after 50+ days in the BC....I have dug a ton of pits and read some lit, but I still need the official knowledge....


as far as I am concerned, I feel like I can safely manage sluff as long as I understand the lower layers and the amount of stress needed to get those layers to slide...

[Your Attorney]

Are there books on managing sluff? (By Coombs or someone similar, I would imagine...)

Yeah. There are few books out there. I read a good one the other day....What's the title......ahhhh I remember.


It's called "I advise you to ski faster, you fucking pansy."

I think you know the author.

[ski_faster]

Did somebody call me?

[homerjay]

Are there books on managing sluff? (By Coombs or someone similar, I would imagine...)

Is this a joke?

[LeeLau]

Good article on sluff management - http://www.verts.com/sarge/articles/...ment_paper.htm

No books that I know of. Your Attorney is harsh but correct - speed is your friend. Getting the habit of making a big ski cut and looking back over your shoulder on the first few turns - another good habit

[Your Attorney]

Ahhh young Maxwell. So much to learn you have. You can delete your post, when someone quotes you, it will live in infamy.

Hence when you find a drunk post, you quote it.

[Max Gosey]

Berzactly. That I know, but the average skimmer does not notice... Or does he? Does anyone here actually skim? Who knows?

I thought there was a lot more to sluff management than just going really fast. My mistake.

[Mountain Junkie]

Managing sluff...so trendy right now.

Seriously, what the fuck are you skiing in Colorado at this time of year that you need to worry about sluffing? If that's "too safe" then I would like to see what your friends are hitting.