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Author Topic: avalanches  (Read 4792 times)

lucky luke

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Re: avalanches
« Reply #30 on: January 21, 2013, 12:19:52 PM »

all I am saying is it is not making the snowpack "heavier", perhaps more or less dense based on what I said above, but atmospheric humidity ONLY comes into play in the formation of Surface Hoar,

density: a. The quantity of something per unit measure, especially per unit length, area, or volume.
b. The mass per unit volume of a substance under specified conditions of pressure and temperature

So if one cubic feet of snow weight one pound and the same one cubic feet of snow weight two pounds...that means that you gain one pounds of some think. The density have increase

can it be done by compaction. In that case, you take a box, place the snow in it and close it hermetically. If you take the density of the box today and in a month...it will be the same. The air trap in the snow is going to be at the top and the solid or liquid part at the bottom, but the wieght by one cubif feet box will be the same if they are no entry or leak.

If you take a feet of snow and keep it in the same condition on the top of the slope: it can loss density by melting,by sublimation and by wind

other way, if you keep the temperature at 25 and just change the humidity of the air for three or five hour, without compaction effect, you will notice that condensation occur, not as hoar, which is a kind of precipitation, but by condensation of water vapor into the same volume of snow.

Yes, there is circulation of air in snow as in " snow avalanche case reports have documented the survival of skiers apparently without permanent hypoxic sequelae, after prolonged complete burial despite there being only a small air pocket on extrication"

In vulgarisation, we lost things. What I am saying is that some people can't make the difference between physical knowledge  and vulgarisation. As it is not what you don't know that will kill you...it is what you think that you know... Those people, with large influence, explained things with a superficial knowledge and make mistake. Mistake that climbers will follow...and they will have an accident.

It take time to understand the theory behind a situation. Some have a pratical understanding of it (climbing bum). Those who survived are the more skill at it and those who didn't climb as much as they said are the worst. As we climb with climbing bum, we gain knowledge that we can explain theorically (they leave by guiding most of the time). That take times and a lot of climbing/reading. After that, those people who explain the theory gave the information to make money (the worse) or to make it accessible for most of us. In doing so, they loose some information. That lost are implify by those who read the book and said I know every thing I can teach you even if I stay in my house at the first sign of snow storm. The results is considerable danger of avalanches with nine inches of snow (every body can see if a place have deep snow or if they saw shrubs between the snow like in huntington ravine)

More than the diference between sport and trad, I think that the interpretation of scientific paper by people without any background is more what will kill our sport. The results is a war of leadership to know who pee father. As the climber climb and the other make public relation...the climber are not there in the important moment, they are in the cliff. So, the mistake done by those who are supposed to be a reference to avalanche are not trustable   
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danf

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Re: avalanches
« Reply #31 on: January 21, 2013, 03:09:36 PM »

David (or anyone esle), luke and not being able to understand what he is trying to say aside, can you explain to me why rounded particles are stronger than crystallized?  Don't think I'm trying to argue here, because I am not- I simply don't understand how that is the case.  I will admit that I have absolutely no avy training and have yet to try to climb anything more than a sledding hill in the snow.  But only way I can possibly understand what you are saying is correct is to assume that the crystalline form of snow flakes/particles is simply more brittle and thus more likely to fracture under load...? 

I guess when I try to envision the snowpack on a microscopic level, the rounded particles seem like BB's and the crystalline form is more like gravel/stone.  The phi angle of BB's is nearly non-existant, while gravel/stone is somewhere around 30 degrees. 

Am I simply thinking about it the wrong way? Please educate this over-educated hole digger....
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DMan

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Re: avalanches
« Reply #32 on: January 21, 2013, 03:31:47 PM »

Gladly, though you should consider joining me in a course if you are really into this. But here's the gist;

First, "stronger" refers to the layer... not the snowpack.

The winter snow pack is made up of layers from each storm/weather event. Strong layers sitting over weaker layers would create a weak snowpack.

Rounded grains bond to each other more readily than "faceted" grains, which don't bond together. They form "stronger" more cohesive layers. "Stronger" does not mean better or safer. Slabs are made of snow that has cohesion, which can be created by wind or rounding... if these cohesive "stronger" layers sit on top of a weaker layer, you have a concern. We look out for "strong over weak" layering, as it is the bond (or lack of bonding) between these layers that could result in an avalanche.

So you can have strong and weak layers within the snow pack. Where they are in relation to each other can promote a strong or weak snowpack.

Essentially, for a nice stable snowpack, you want the strongest layers on the bottom, progressively getting weaker towards the top, with no strong sitting over weak. This is what we get by late Spring when the snow in Tucks is concrete, with some nice weaker corn on top.

Our biggest concern on Mt. Wash is almost always wind slabs (sometimes storm slabs), but when you take a ski pole or ice axe and push through a foot of dense wind effected snow and feel soft less dense snow below, there may be a stability issue there... there are ways of testing the bonding in those layers outside of what I'll try to explain here.

Does that help? Sometimes I feel I go to far with explanations :)
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danf

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Re: avalanches
« Reply #33 on: January 21, 2013, 04:02:22 PM »

I think so.  I'm interested to the point of internet understanding right now.  I don't do any sort of trekking at the moment, that was my ex-wife and she never wanted my company (which is part of the reason for "ex") when she hiked at any time regardless of season.  I still don't know if she has made a winter time ascent of Washington, but I know it is on her "to-do" list.  I do know she won't do it by herself though, pretty sure Joe Lentini was supposed to take her at some point and with him in the lead I don't think I need to worry too much about our kids being left mother-less....
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lucky luke

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Re: avalanches
« Reply #34 on: January 22, 2013, 04:14:14 AM »

http://avalancheinfo.net/fixed/weather/glossaries/advanced/advdefs/metamorphism.html

So, what to remember? "Through metamorphism, the form and size of snow crystals and grains inside a snowpack change continuously, altering the strength characteristics of the snowpack. If it is altering the strenght characteristics of the snowpack, snow flake with point are more stable than when metamorphosis alter the strenght characteristics of the snowpack.

Powder avalanche in mt washington is pratically inexistant because the place where the snow can form a slab in steep terrain are limited and because the quantity of snow is not of three or four feet like in some other mountain. I was in the mountain in some white out and I can told you that the size of those avalanche are very small. Those avalanche are influence by the humidity of the air.

As the wind is cold and the bottom of the snowpack is warm, a crust can be formed on the surface of a snow field. With metamorphosis, the fresh snow on the surface of the field froze. It is cause by the vapor from the snow pack, the humidity of the air, a freezing rain, the sun, etc. The result is a crust of ice over fresh snow. As the snow begin is metamorphosis, it come more compact and create a pocket of air between the crust and the snow...we have "slab avalanche". Waking on it is safe, but when the crust broke you are in danger. Damnation and yale are very treacherious for that.

At the begining of the thread, I say that it is more dangerous after a snowstorm...because slab avalanche can be trigger....than during the snowstorm....because there is not a lot of steep section where the snow can built and gain enought energy to make a dangerous powder avalanche. And that they rate the danger more dangerous during the snow strorm than after.

Dman said: "Our biggest concern on Mt. Wash is almost always wind slabs (sometimes storm slabs),"

No trustable?

Nb, there is also wet avalanche. I was close to a wet avalanche like the one who kill people on mt washington. The wind create by the slide blow my tent down...even if I was inside!!! close call

       
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DMan

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Re: avalanches
« Reply #35 on: January 22, 2013, 07:50:29 AM »

You continue to pass incorrect information.

A “Powder Avalanche” by definition is an avalanche that has gone completely airborne AND has no associated mass behind it. It is all aerosol. We don’t get them as we don’t have big enough steep terrain. They do happen in bigger mountain ranges.

You are referring to a “Point Release” or “Loose Snow” avalanche. We get those during heavy snow events. Small ones are sluffs. Sometimes they are bigger enough to bury.

Slabs form AND release during storms... so “more dangerous after a snowstorm” is a poor statement. Hillman’s Highway ran D4 a few years ago and wiped out 3 acres of 60 year old pine trees... during a snow storm...

Again, more people get caught after the snowstorm because they are smart enough not to be there during the storm if the rating is Considerable+... except you.

"Dman said: "Our biggest concern on Mt. Wash is almost always wind slabs (sometimes storm slabs),"

No trustable?”

I said biggest concern, not only. Wet slabs & wet point release are both issues any time there is a lot of free water in the snowpack (spring time, during rain, etc).

Also, the “air blast” as talked about that can proceed an avalanche is no more than a small gust of wind. If it was not windy at the time, and you felt the air blast from an avalanche, you really are a lucky luke.
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JJ Jameson

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Re: avalanches
« Reply #36 on: January 22, 2013, 10:25:53 AM »

Luke, earlier you state:
 "When I looked at central couloir, I don't see two or three feet of snow. Even with zero danger of avalanche, if someone don't kick hard enought to touch the ice...he will fall bringing snow with him. With the warm temperature and the big big big 9 inches of snow..."

You truly do not seem to be understanding the idea that isolated slabs can, and do occur all over the ravines, and that these can and will slide, by themselves, or with a human trigger. You don't need a lot of snow, and typically these slabs will form on lower angle portions of all the gully climbs.(exactly as described in the bulletin... there is a reason he included that very specific info)

Wind, and ANY snow precipitation can cause this. Wind, by itself, AFTER snow precipitation can cause this.
This photo shows a well consolidated wind slab over two meters tall in Tuckerman's Ravine. This was the result of a 6 inch snow fall, followed by 90 MPH winds. The overall snow depth depended entirely on terrain features, loose powdery snow evenly spread, to areas with no trace of snow. This slab was at the base of a buttress, so digging a pit wasn't putting us at risk.
 
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DMan

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Re: avalanches
« Reply #37 on: January 22, 2013, 10:31:20 AM »

Great photo JJ. Love needing a step stool to carry out a compression test! ;)
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lucky luke

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Re: avalanches
« Reply #38 on: January 22, 2013, 11:23:19 AM »

This slab was at the base of a buttress, so digging a pit wasn't putting us at risk.

I don't say that avalanche are not dangerous, but avalanche is more dangerous after a snow storm. I walked in hips-shoulder deep snow at the bottom of pinacle asking me if what I was doing was right. In pinacle, a corniche can form in the gully at the top 0f the third pitch and, in some condition, of humid air, it can fall as loose snow. But I didn't see it often. Walking in deep snow was better than in the avalanche path.

It is easy to understand that with rock shoes, you can friction up a slab and there is a time when the feet will slipt??? So, at the difference of rubber, it is snow flake point that make friction. A sharp pick have always better friction than a round ice, which act as a bearing in a wheel. So, for powder and wet avalanche, you have all the theory you need. The rest is judgement like the one you did: "so digging a pit wasn't putting us at risk"

Slab avalanche can be made the first snowing day and increase in danger as the season go on. a pocket of air is predictable by the shape of the slab and there is technique to identify them. It can settle by themselve, trigger by human, by humid snow more than dry, and by a lost of mechanic tension (some are grade wet, but are wind avalanche). So, I never say that the danger is less than the day before. I said that the danger is less than the day after...

So, when you follow the avalanche risk: first day is low avalanche danger. second day is extreme danger and four and fift days, it is moderate so the quantity of tourism not expecting an avalanche is higher. When you understand that some climber say: "I am 5.10 rock climber so I can transfer my knowledge from rock to ice...I am sure that they never climb without t-shirt in a blizzard at the summit of Mt Washington". For them no danger of avalanche is no danger at all.

Avalanche awardness must change. Actually, it scare people and people don't learn technique to save there ass. Avalanche awardness are no-trustable. Always be ready for extreme avalanche activity and decide by yourself.

Burrying people with a lot of paper information on snow metamorphosis to show that we have a full case of knowledge and beeing caught by a powder-slab avalanche in a snow storm (yes it's happen to me) is very different. My partner walk directly in the weakest point of the slab. We were rope up and he didn't loose his equilibrum, but it was very scary.     
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DMan

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Re: avalanches
« Reply #39 on: January 27, 2013, 09:49:14 PM »

If you are still reading this thread I just came across a great blog post from an avalanche survivor I wanted to share:

http://blog.mec.ca/2013/01/23/the-finger-of-god/

LL, What ever you think is being taught in “avalanche awardness” courses is quite different from what is being taught in AIARE courses in the US. We do not teach fear, but a balanced approach of decision making, snow science, human factors, and honest self-assessment. We encourage people to travel in all danger ratings, but to be sure their terrain choice matches both the conditions and their understanding of the problem.

Your countless “scary” experiences indicate that you may be stuck in a “non-event feedback loop”, i.e. you get away with climbing in high danger days so it re-enforces you made the right choice...

1) “My tent got hit by air blast from avalanche”

2) "My partner climb on weakest part of slab and it was scary”

3) “Yes I got caught in powder-slab avalanche"

You may be simply rolling the dice my friend...

It’s a lifelong passion learning about the snow... no expert claims they know everything... but no one should shun learning more...

An AIARE 1 course is 3 days long. No one should expect to be an expert at anything after 3 days. It is a foundation (and a good one based on feedback from 200+ students who have gone on to climb all over the world).

Competency takes practice and time in the mountains... but we need to start somewhere.

The words you use to describe processes can really confuse people who only speak English.

Your point is often lost in mis-intrepretation.
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lucky luke

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Re: avalanches
« Reply #40 on: January 27, 2013, 11:46:23 PM »

You may be simply rolling the dice my friend...

It’s a lifelong passion learning about the snow... no expert claims they know everything... but no one should shun learning more...

Rolling the dice is pure hasard. Maybe I learned about the danger and how to avoid it in real situation more often than theorically. It is clear that what I know about avalanche as pratical knowledge make many situation safer for me than for you. How can you know? the worse you did is climbing omega first pitch at canon in a snow storm.

The argument`you won't be always lucky...is a good way to scare people. As I climbed for more than 25 years...I can talk about a lifelong passion learning about snow with real situation. The most important thing is that I climbed many winter in very different condition that you cannot imagine and, even with a bag of trick, I can bail in the most beuatifull sunny day after a storm, with a low avalanche danger, because it is too dangerous for me. and nobody will take a decision for me on my safety, even if I can be a good second.

 
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darwined

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Re: avalanches
« Reply #41 on: January 27, 2013, 11:55:49 PM »

You may be simply rolling the dice my friend...

It’s a lifelong passion learning about the snow... no expert claims they know everything... but no one should shun learning more...

Rolling the dice is pure hasard. Maybe I learned about the danger and how to avoid it in real situation more often than theorically. It is clear that what I know about avalanche as pratical knowledge make many situation safer for me than for you. How can you know? the worse you did is climbing omega first pitch at canon in a snow storm.

The argument`you won't be always lucky...is a good way to scare people. As I climbed for more than 25 years...I can talk about a lifelong passion learning about snow with real situation. The most important thing is that I climbed many winter in very different condition that you cannot imagine and, even with a bag of trick, I can bail in the most beuatifull sunny day after a storm, with a low avalanche danger, because it is too dangerous for me. and nobody will take a decision for me on my safety, even if I can be a good second.

Wow! Arrogant much?
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Jeff

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Re: avalanches
« Reply #42 on: January 28, 2013, 08:53:55 AM »

Lucky Luke: I don't get it-- you want to inform people so that they will enjoy climbing and learn through experience and good judgement and you recommend learning from a number of people you consider "masters" such as John Bouchard, Base, SA (who often posts here), Yvon Chouinard and his ice climbing book, Freedom of the Hills-- which according to you is the BIBLE ( I too have read it in several editions, starting with Edition 1, which I'm old enough to have bought when it was the only edition). DMan is an experienced climber and guide who has made avalanche study and education a big part of his work. Yet you seem to be offended that he is trying to help others gain valuable knowledge without having to go through the "trial and error" route that you and I may have used in our apprenticeships. I started climbing frighteningly near 50 years ago in the French alps near Grenoble-- in 1974 I nearly triggered an avalanche while skiing in a storm at Val d'Isčre--a convex slope we were traversing in whiteout  "thumped" and I dropped about 18 inches (my wife, new to skiing and trusting my "knowledge and experience" and two friends were following me). The next thing to "thump" was my heart, rapidly, as I executed a kick turn and said "GO BACK". We escaped, but it could have been tragic. Years before that, a partner and I decided to climb Pinnacle Gully as our first NH ice climb. It had only that year been climbed without cutting steps, and since we had been in the same Yvon Chouinard ice climbing clinic in the Adirondacks as Jim McCarthy (who, with Rick Wilcox), did the first ascent without step cutting that year, we figured we might as well "give it a go". We climbed in a blizzard and all went well, until our descent-- we planned to descend the Escape Hatch or South Gully but we went too far (zero visibility, moving cairn to cairn, getting dark, etc) and descended the Ravine of Raymond Cataract in thigh deep snow. This was the year that the big slide devastated trees below that cataract all the way across the Huntington Ravine trail leading to the Harvard Cabin. Why we didn't trigger a slide and suffer from our inexperience, I've never understood-- I attribute it to blind luck. As I've continued to ski and climb and learn a bit more through avy courses, reading, and talking to more knowledgeable folk than I, (Dman among them) I have become safer (but NOT SAFE)-- I recognize that the risks can not be eliminated; indeed that is part of the appeal of the mountain life. As you know, I also guide, and teach new skiers and climbers, trying to mentor them as I was once mentored . As I believe you are, Dave and I are still learning and improving our mountain craft. That is why I started this note by saying "I don't get it". I don't know why you seem to have to take a contrary position to every post Dman puts up. Perhaps you and I should discuss it in French some day, since we are both fluent in that language. Until then, bonnes courses!
Jeff Lea (full disclosure : I work for the EMS Climbing School and Wildcat Ski School-- these opinions are my own, and not those of my employers)
« Last Edit: January 28, 2013, 09:08:33 AM by Jeff »
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strandman

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Re: avalanches
« Reply #43 on: January 28, 2013, 09:24:35 AM »

You can  predict the snow- sometimes- and then again.. I think Alex Lowe might have been considered an "expert"  dead in an Av..JB also i would say expert avved approaching a climb he did the f/a of !

Once again that Freedom book of BS
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DMan

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Re: avalanches
« Reply #44 on: January 28, 2013, 10:18:05 AM »

You can  predict the snow- sometimes- and then again.. I think Alex Lowe might have been considered an "expert"  dead in an Av..JB also i would say expert avved approaching a climb he did the f/a of !

Once again that Freedom book of BS

It can be very hard to predict what is happening over a mile away and thousands of feet above you.... McLean speculated it was probably caused by lee wind-loading. Spend enough time in big mountains, and we all know this might be an outcome. IMO there is a big difference from being caught by such a massive natural slide so far from the start zone and being the one to trigger it when there are warning signs of unstable snow...
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