Punching into crevasses: skis vs on foot

Trying to garner some more information on something that's always gnawed at me. Are you truly less likely to punch through into a crevasse or bust a snowbridge while on skis as opposed to on foot? It seems that I and many others have at least the superstition that being on skis will minimize your PSI on the snow and thus your chances of falling into something. But can this be in any way verified? Anyone have a first hand experience with having crossed something safely on skis that failed for persons nearby when on foot and shortly thereafter? Any authorative information out there about this subject?<br>To play devils advocate for my own superstition: if whatever you're about to fall into will fail the width of an entire ski, seems like being on skis wouldn't have helped. And, if you happen to weight a strong turn on top of a failure point, the PSI might even be higher while skiing. Thoughts?<br>This brought to my mind by the Inter rescue of last weekend. In most cases I've heard of people falling considerable distances into an Inter crevasse, they were glissading at the time. Having your eyes less than 3 feet above the snow surface cuz you're sliding down fast on your butt with snow flying from your feet and limiting visibility - a factor? I've glissaded right into small bergschrunds because of this in the past, before I more or less gave up sitting glissading for other safer pursuits.

If the crevasse opening under the snow bridge is less than the length of a ski, clearly skis keep some of your weight off the crevasse. This certainly reduces the risk by some finite factor, which I won't attempt to estimate.<br><br>Weighting a turn may create more pressure, but that will be because of your speed. Your speed limits your time over the snow bridge. <br><br>Let's assume you travel at 10 m/s (~22 miles/hr, a very reasonable skiing speed). If you are above a crevasse opening below a snow bridge that is 2m wide, this gives you about .2 seconds above the abyss. In .2 seconds, gravitational freefall is only (1/2)*9.8(m/s^2)*(.2^2)~1meter. <br><br>The same analysis for 15 m/s (~33mph) results in a fall of less than 1/2 meter, in which case your speed would certainly carry you over the crevasse, albeit leaving you in a tumble. <br><br>Thus my answer is: skis certainly are safer. The bridge isn't likely to collapse until you are somewhere near its center, so you might be able to add a factor of 2 into the equation, meaning you only would have fallen less than a foot on the 2m bridge skiing 22mph. I think skis help a great deal. <br><br>This analysis also suggests the safety conscious should ski fast!<br>

That's a good analytical spin Sky. <br><br>Here's an irrational desk jockey's conglomerated jumble of misguided assumptions for a measured look at the opposite spectrum of reality - opinion. Often people question my use of climbing unroped. One should note, though, that it's not the climbing that concerns me, but the descent. If I had to plunge step down a glacier I would without a doubt be wearing a rope, but with skis chosen as my weapon of choice, the maneuverability and speed opt for less risk in my opinion. Of course that assumes that one doesn't ski into a crevasse due to unchecked enthusiasm ;D As for skinning, I used to believe that was safe also until I fell in a crevasse, so I am less willing to assume that one shouldn't be roped while skinning up a glacier, especially in winter while climbing on wind deposits which are notorious for covering up and smoothing out a(n) otherwise giant gaper(s). But back to your original question, is skiing unroped safe? To answer lets first look at the alternatives:<br><br>1. Ski roped<br>2. Downclimb roped<br><br>If you ski roped are you placing pro? If not, how much safety does the rope offer? With skiing, I think it just gets in the way and puts too much dependence in the hands of your partners, more so than climbing because it&#8217;s easier to make a mistake skiing because the rope can get in the way of both your attention and skis. I think this is something that the sport may have to mature too or accept as a necessary risk. I don&#8217;t know. In a way it is a deterrence for lesser skilled individuals, where as a rope can work as a crutch to justify lesser skilled individuals to venture where they may not be ready too. Of course this applies even more to steeps, but that&#8217;s a whole other bucket of worms. I do plan on using a rope more on steeps but only to lessen risks at certain cruxes, not to ski an entire route roped. <br><br>As for downclimbing roped. I love to ski and this is part of the experience. If I&#8217;m going climbing and there is snow you can expect my skis will be on my back. <br>

The fact that you are less likely to punch through into a crevasse with skis on is evident/displayed even off of glaciers. Verification comes when the snow starts melting in June and lower elevations expose creeks, rock, stumps and downed trees with many bridges, moats and holes. (although possibly on a smaller scale) When skinning (slow) and/or skiing (fast) at any temperature and in any snow condition, you can test this; (I have many of times and you should too, especially if your superstitious) skier moves across, hiker behind, punches in to his armpits (just introduce someone to the sport and have them hike up behind you! They'll love it.)......As for gaping crevasses? Scout them out (photos,recon,TR's), wear the skis going up (if possible), assume the risk, and be prepared to extricate. I think you are truly less likely and this IS AUTHORITIVE INFORMATION. (Note: any of the above may be wrong on the day you go ski) Now, call the Witch Doctor. 555-WHAT.

I agree fully with Toby. Anyone who doesn't feel more vulnerable on foot than on skis need only experiment a bit with thinly-bridged streams. First, walk across on skis: feels safe, solid, and secure, right? Now take off your skis and boot across the same bridge. Don't forget to bring a dry pair of socks.

Hmm. I like Sky's analysis. I've never thought of the perspective that every moment you spend on top of something suspect is actually a moment of suspended free fall, so maybe you oughta minimize it. (Sometimes that's a good tactic when scrambling talus and choss, too.) I'm not sure that stream undercut bridges and crevasse bridges equate 100%, crevasse bridges have a lot of other factors at work. They aren't melting out nearly as much from below; in many cases they start to fail naturally because the snow bridge is actually being stretched out too far laterally, rather than being ablated and thinned. In that case it's a system under tension, where any piece of the system might fail under your weight and not necessarily the very thinnest part. Also, crevasse bridges tend to have a bunch of odd intermediate layers where you might only partially fail it.

Hmm. I'm not sure that stream undercut bridges and crevasse bridges equate 100%, crevasse bridges have a lot of other factors at work. They aren't melting out nearly as much from below; in many cases they start to fail naturally because the snow bridge is actually being stretched out too far laterally, rather than being ablated and thinned. In that case it's a system under tension, where any piece of the system might fail under your weight and not necessarily the very thinnest part.

<br><br>No doubt this is to some extent true, but it's difficult for me to imagine that it makes much difference in real-world terms. How much tension operates in the average snowbridge? How much difference does the specific source of the (bridged) hollow space below make?<br><br>

Also, crevasse bridges tend to have a bunch of odd intermediate layers where you might only partially fail it.

<br><br>I'm not clear how the presence of intermediate layers might change the equation of skis = greater safety. <br><br>I also like Sky's analysis, probably because I already believed it true, although I'd not conceptualized it in terms of measurable downward acceleration. Back to that stream-crossing analogy: I've often had the experience of skiing across a thin bridge as it collapses under my skis. If I'm moving fast enough, I make it to the other side. A dull, plodding pace (my special talent) means I fall through.<br><br>Last, although there is no doubt that a heavily-weighted turn exerts more force on that achetypical snow bridge than a more subtle weight shift, it's hard to imagine a turn weighted so emphatically that it corresponded in pounds per square inch to the average plunge-stepper. That's why even big, gorilla-like skiers like myself float along with big grins on our faces, while descending climbers grimace and cuss and posthole all afternoon. <br><br>Of course, I'm willing to be proven otherwise on any or all of the above. <br><br>Enjoy,<br><br>Mark

I agree with much of this reasoning, seems we all have justified to ourselves in one way or the other that it is safer to be on skis. Without a doubt there is way less chance of falling through on skis. But then the tradeoff is that on the ascent (assuming you are roped) it may be harder to self-arrest if there is a problem, and on the descent it just isn't practical to ski roped. Or has anyone tried this? I, like Jason, have contemplated "belay skiing," but that I would do only with a belay anchor, and that would get tedious if you had to do it more than once. Plus you never know if you are belaying from atop a snowbridge...<br><br>Speaking of belay-skiing, do any of you guys set up a belay anchor for doing ski cuts on avy slopes?

I've down skied roped up on a glacier in the alps. Very interesting experience - 4 on a 50M rope. Takes discipline on everyones part. First persons leads doing tight controlled turns, followers try to stay in the same track and be alert for the need to speed up or slow down. Last person has the hardest task, due to the "crack the wipe" factor. Helps if everyone is a good skier..... This was on lower angle glacier, doesn't apply to terrain where you feel the need to set a anchor due to steepness. I would want only 2 on the rope in those conditions.

I've heard of people ski cutting a slope roped though not as much here in washington. This isn't a technique I have used, but have definately wanted to in the past. Now that I have my nice 20 meter rope, I'll be using it more often, especially when I have even a remote avi concern. <br><br>Back to our other subject though. I have something to add that is nothing more than an observation and a call for an opinion. I was looking at a UK skiing website and they were talking on and on about crevasses and how 'we' are crazy to be skiing on top of snowbridges. I say 'we' because they used some photos of myself and brother as examples. Here is the picture they used, which they considered insane. I'm interested in what the general BC skier thinks here:<br><br> <br><br>

To Jason_H, I like this photo best:<br><br>

Getting off topic, but I really like this one of Josh ;D<br>

;D Those don't help my case, do they?

Um, ah, No

This new topic is more fun. A lot more visual...

Great topic, wolfs. And great input from all.<br>I know while on foot I have punched one leg through (and pitched forward to arrest) but never even come close on skis. <br>My thoughs to some of the respondents:<br>

... and how 'we' are crazy to be skiing on top of snowbridges. I say 'we' because they used some photos of myself and brother as examples. Here is the picture they used, which they considered insane. I'm interested in what the general BC skier thinks here:

<br>Jason, I've skied over cracks maybe as much as half that width and didn't consider it particularly hazardous; I'm sure if I skied as well as (I perceive) you do I would not hesitate to ski that which is pictured (in the shot YOU posted), in the right conditions. As for the pics that Jeffey & Sam posted of you, well, um, ah... It's kinda fun to find yourself being used as an example without your knowledge, isn't it <br><br>

...But then the tradeoff is that on the ascent (assuming you are roped) it may be harder to self-arrest if there is a problem, and on the descent it just isn't practical to ski roped. Or has anyone tried this?

<br>We have done a lot of (uphill) roped glacier travel on skis in the mountie's annual ski GT class. While I agree that arresting a fall is a bit more problematic with skis on, we seem to get by ok. Of course we don't do two person rope teams; that could change the situation considerably. Also on one occasion we descended the glacier roped on skis (which I was definitely not looking forward to). What happened was that the fog had come in and the visibility had diminished to about 10 ft. We had marked the crevasse hazards on the way up with wands but we were not confident everyone would see the hazards in time, swooshing down the glacier on skis in the fog. What we decieded to do was rope up and put our skins on so that everyone could SLOWLY inch their way down with each rope team leader staying in sight of the tail end of the rope ahead. It took a while but I guess it worked ok 'cause we didn't lose anyone <br>That's the only time I've skied downhill roped (if you can call it that) and like others point out I have no interest in improving my roped downhill skiing skills. If I'm going to climb it, I want to (at least start out intending) to ski it. <br> <br>

...Speaking of belay-skiing, do any of you guys set up a belay anchor for doing ski cuts on avy slopes?

<br>I happen to be quite fond of belayed ski cuts, especially in chutes where there's no exit if it slides, or any other place where a ski cut leaves safety in question. We've gotten so that we can set them up pretty quick with a partner's skis and then the tester can safely literally bomb the hell out of a chute with his or her body by just jumping into it with skis on. The other thing that appeals to me is that once the tester is happy with the results and is ready to ski the slope he/she can have the belayer take out all the loops and knots on the other end of the rope and then ski on down dragging the rope behind (still tied in). If it was a bad call the resue should at least be fairly quick as it is unlikely the rope will be completely buried. <br><br>

Let's assume you travel at 10 m/s (~22 miles/hr, a very reasonable skiing speed). If you are above a crevasse opening below a snow bridge that is 2m wide, this gives you about .2 seconds above the abyss. In .2 seconds, gravitational freefall is only (1/2)*9.8(m/s^2)*(.2^2)~1meter. <br>The same analysis for 15 m/s (~33mph) results in a fall of less than 1/2 meter, in which case your speed would certainly carry you over the crevasse, albeit leaving you in a tumble.

<br>Yeah, I'm not sure I'm smart enough to follow all that but is sounds really good to me... and I guess the smaller the crevasse the better. The skis certainly would seem to bridge the smaller crevasses; my biggest concern skiing down is that at the completion of the turn my skis are across the fall line (presumably in line with the typical crevasse) so the bridging effect will be minimal. So, Sky, I guess following your practice and theory of skiing straight down the slope without turning would minimize that risk, eh? <br><br>

I've heard of people ski cutting a slope roped though not as much here in washington. This isn't a technique I have used, but have definately wanted to in the past. Now that I have my nice 20 meter rope, I'll be using it more often, especially when I have even a remote avi concern. <br>

<br><br><br>To continue on the tangent.....Many times I have wished for a rope before ski cutting a slope and kicking cornices. This technique would really open up some mid winter chutes with localized instabilities such as wind loaded entries with no place to "safely" ski cut. I would be a little more concerned if this procedure was used to ski open slopes with a wide spread avalanche concern, but for localized stuff, could be just the ticket.<br><br>Back to the subject......There is always someone or group that think everything, lets call them adventurous skiers, do is crazy. It all comes down to your skill and the level of risk you are willing to accept. Ok......we are taking about UK skiers right.....do they have mountains in the UK? I find it funny they choose that relatively tame picture of a crevasse jump over others I have seen. The skier appears to plan that jump quite well, looks like a great glory shot and a good day at the office.<br>

Yea, I thought of that UK thing. ;D <br><br>Do you have a link to these sick crevasse pics I'd like to see them...<br><br>

Sam and The Gaper have essentially posted proofs of my theory by taking the limit as snowbridge thickness goes to zero.  If it is true in this limit, intuition certainly suggests the effect will work well on snowbridges of finite thickness.  I never thought I'd see a Hummel complete a derivation for me, way to go Josh!<br><br>~Quod Erat Demonstratum~

Corked 360 over a crevasse no less.<br><br> www.skipressworld.com/us/en/magazine/200...r2004vol3no03a19.htm <br><br>There are some French extreem skiing/boarding films that take it to a different level. 60-70 degree to raps and a jump to finish it off. Two years ago at a bar in France they were showing these films, unreal. The only catch, not many live very long..... ??? If I can find a link to those I'll post it.<br><br>

Well, there are UK skiers with skillz, but they probably don't stay in the UK that long. Check out this guy's site:<br><br>www.philingle.com/index.asp

I like Sky's math analysis. Confirms my thoughts that it's easier to do things faster. Like if you run a marathon in 3:00 that's easier than 4:30 because you don't have time to get so dehydrated, footsore, hungry, mentally worn out, etc. and you don't have to carry so much water and food or wear heavier clothes. Not that I can ski fast. <br><br>One more question related to weight on snow: Is it safer to go behind my 300 lb buddy assuming anything he doesn't break through is safe for my 145 lbs and lighter gear? or should I go first so he doesn't weaken it just enough for it to fail under me? ???

At 200+ lbs, I punch through crusts that others float on whether I'm first or last. I doubt it makes much difference. <br><br>Can you put me in touch with your 300 lb ski buddy? He sounds like he'd make an outstanding snowbridge tester?perfect for these sultry mid-summer days.

<br>Can you put me in touch with your 300 lb ski buddy?  He sounds like he'd make an outstanding snowbridge tester?perfect for these sultry mid-summer days.  

<br><br>.....unless your roped up.

Wolfs - is what you're, in essence, whether it is really PSI that matters on wide bridges, or simply total weight? In other words, are most failures on such bridges of the posthole nature, or are they total bridge collapses?

Wolfs - is what you're, in essence, whether it is really PSI that matters on wide bridges, or simply total weight? In other words, are most failures on such bridges of the posthole nature, or are they total bridge collapses?

<br><br>From experience, i can't say which in particular (collapse or punch through) is more prevelant but I can say I've experienced both. One nugget of advice that I'd like to pass on is this: don't stand 2ft behind your partner. In other words, leave some room. It makes a difference, even if it's only 10 feet. Of course if you were on a rope this wouldn't really apply (I assume the rope is tight), in these cases I wasn't. I just think its a good policy even if the best policy is to be a smart climber. The thing is, we're not always as smart as we would like to think. Avi wise it's not a bad idea either. You just never know...<br>

Yes, Sky's math analysis is common sense for the decent....I was assuming this was for ascent!!!! Going up, you are not traveling fast. So this is more of a concern to me.....Why would you walk/climb on glaciers up a worthy ski peak to walk/climb down? To me thats just not logical...Ski fast and try to work some style into those turns!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Wolfs - is what you're, in essence, whether it is really PSI that matters on wide bridges, or simply total weight? In other words, are most failures on such bridges of the posthole nature, or are they total bridge collapses?

<br><br>That was sort of the gist of my original question. I think it's pretty obvious that being on skis rather than on foot will prevent a lot of falls into stream hollows etc. or in at least some crevasse crossings where what matters is how much weight is put on a section of snow that happens to be the thinnest, and how much surface area that's spanned over. The 'superstition' part is whether that evidence is enough to convince you that 100% of all possible scenarios where a crevasse is bridged with snow are going to be better while you're on skis, better enough to convince you that maybe if you're on skis you don't need to rope up. The exact physics of how some unseeable crevasse crossing happened to fail will be academic to you at the point where you find yourself wedged head down 50 feet deep in the freezer, you just don't want it to happen period.<br>As far as the down part - skiing glaciers roped is so undesirable that I didn't really consider it to be part of the scope of my original question. You either ski the damn thing or you don't, or at least you limit being roped to a small percentage of the descent that seems the worst. Otherwise the whole idea of skiing it is a bust. (I agree though with something that Amar said in the original TR thread that got this rolling - he mentioned that he skied the Inter alright after the incident, but wore his harness. Read the related accident report on cascadeclimbers for why this simple precaution might make all the difference in the world if you DO punch in, so long as you're still findable and alive.)<br>I was originally thinking mostly of 'up'. The 'down' analysis that Sky started in on is relevant too, in that it's something to think about as you cross all the known bridged points.<br>Also: I hope to god that we ARE crazier than the Brits, at least when it comes to skiing. I mean come on, this is the country that produced "Eddie the Eagle"...<br>Maybe for an upcoming TAY gathering, we could have the more adventurous adjunct of our virtual group go down to the lower Coleman or something, and build up a whole series of linked kickers on the edge of crevasses, and mark em up nice with spotting dye and flags and maybe buff up the landing zones a little. It'll be like a backcountry terrain park. Some of us approaching-the-crest-of-the-hill folks might even venture to pop one or two of those if they are nicely prepped ;D

sounds like Sky is rubbing off on some with the use of the word nugget