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An Unfamiliar Hazard: Rock Crevasse
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An Unfamiliar Hazard: Rock Crevasse

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An Unfamiliar Hazard: Rock Crevasse

Page Type: Article

Object Title: An Unfamiliar Hazard: Rock Crevasse

Activities: Mountaineering

 

Page By: splattski

Created/Edited: Nov 16, 2010 / Nov 16, 2010

Object ID: 679211

Hits: 4188 

Page Score: 95.18%  - 51 Votes 

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Spring in the mountains

 
Down to the saddle
Moving down to the saddle

It was a beautiful spring day in the mountains. Middle of May, actually. And it promised to be quite warm. We hadn’t even made it to the summit and we were already in short sleeves. Although the snow had been rock hard when we started, it was softening nicely now and it looked like later, as it warmed up, the pristeen slope was going to be a corn fest, a tele skier’s dream.

Snow features

 
The cirque
The cirque

Near the false summit of the ridge, some rocks were exposed. Don’t step too close; there is always that hazard of falling down between the rocks and the snow, which by May has melted away from the rock. Ooops! Too late. I went in with a grunt, well past my knee. Fortunately, it was no big deal. I leaned on both my ski poles and hauled myself back into an upright stance, and continued on my way; up, over, and down toward a dip in the ridge.

The dip in the ridge was really sort of a saddle, the top of an arcing cirque with huge cornices dangling over a steep bowl. The way the cornices were jammed together and leaning over the bowl reminded me of the inside of an igloo. The overhanging dome of an igloo consists of snow blocks, each block required to hold its neighboring blocks in place. On the far side of the saddle, the final ridge angled gently toward the highpoint, and I was already anticipating the awesome views that should happen from there.
 
Drawing
Diagram showing gap between snow and rock wall

As I worked down the last bit to the saddle, I looked again at the huge cornices. Cornices always give me the willies, and these were monsters. Twenty feet, thirty feet, maybe even taller. They were going to make a real ruckus when they decided to let loose. With the heat building so quickly this morning, maybe today was the day? With that thought fresh in my mind, I cautiously moved away from the edge. Then I moved a little farther just in case. OK, now I was waayyy back. Nothing to fear.

What the heck?

 
In the hole
In the hole. Note thinness of snow covering the crevasse.

I confidently crossed the saddle and started up the other side. Kicking steps up the final ridge, I started to blow a bit of air. Ah, altitude. Plus, we were making really good time. The little voice in my head said just keep kicking. Work those poles. Kick. Plant. Kick. Plant. Feel the rhythm. Listen to your breath. But wait… in addition to my huffing and puffing, there’s another noise.

When I turned around, what I saw greatly alarmed me. Or maybe it was what I didn’t see. Because all I saw was the last 12” or so of a pair of ski poles sticking out of the snow, baskets up. And what I heard was sort of a muffled “hmmpph.” What the heck?

I charged back down the slope, following my steps but keeping my eyes on the poles. They were moving, and slowly getting longer. Charlie, who had been behind Jim, got to Jim about the same time as me. When we got to the ski poles, we were both dumbfounded. What we saw was Jim down in a hole, head starting to slowly emerge. He had fallen in a rock crevasse.

Definitions

Now before I go too far, I have to straighten out some language. In a google search, I found lots of hits for “rock crevasse.” But to me, the links I followed were misusing the term; they were calling any crack in the rock a crevasse. So here are some dictionary definitions:

Crevasse: A deep open crack, esp. one in a glacier
Crevice: A narrow opening or fissure, esp. in a rock or wall





Aftermath

 
The hole
Hole marked by red arrow. Note "safe" distance to edge of cornice

So as I am using the term, a rock crevasse is a crack in the snow with rock on one side. It is the result of the snow moving away or melting away from the rock. I had stepped in a small one earlier, but Jim had fallen in more than eight feet deep. And that was without making it to the bottom!

Charlie and I were very concerned for Jim, maybe even a bit in shock. But Jim had a different viewpoint (below the surface), pointing out that each of us was standing right on top of the crevasse into which he had just fallen. So we moved to safer stances to help extricate him. Because the snow was soft, Jim couldn’t get purchase to climb out on his own. So we sort of half-hauled him out.

All except his hat, which had gone even deeper in the hole and disappeared. He wasn’t too interested in going down to look for it.

Images

In the holeThe holeDown to the saddleThe cirqueDrawing

Comments


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Viewing: 1-19 of 19    

Deltaoperator17Nice Topic

Deltaoperator17

Voted 10/10

Good writing Mr Splattski. :-)
Posted Nov 19, 2010 12:05 pm

splattskiRe: Nice Topic

splattski

Hasn't voted

I'll take you up there next spring!
Posted Nov 19, 2010 5:29 pm

relicThis terrain danger does need a good name

relic

Hasn't voted

This is the first place anywhere I have ever read anything about this, great topic.
I do a lot of spring skiing, and I’ve had a several experiences with this. Two didn’t even involve a cornice or obvious ridge edge. The most dramatic one occurred in the middle of a long open slope, one that I’m sure in summer would be a simple talus slope, but in the early May of my visit was smooth, inviting, obstacle free traverse to allow passage to the next pass I was headed for. I was on skis, and without warning, I dropped through, stopped at the shoulders only by my arms being outstretched and my pack behind me. I’ll never forget the feeling of hanging free from the chest down, both feet swinging freely in the air, skis still attached, while I tried to keep my upper body still so as to not break though the snow surface. After a moment, a ski touched rock to the uphill side, and I managed to set a metal edge on a nubbin that held, giving me enough leverage to lift and then roll to the downhill side and out. The hole turned out to be a good 12 feet deep, bottom was a pile of talus rocks, The big rock that I got the ski edge onto turned out to be a massive boulder; as you know talus slopes often have house-sized boulders and this was one of those. Scary, and really taught me to expect these holes anywhere. Might be more prevalent here in the Cascades because of our massive snow accumulations.
So was your experience and those photos in your home area of Idaho/Sawtooths? Looks a bit like the eastern Cascades.
Posted Nov 21, 2010 12:52 pm

BobSmithHell!

BobSmith

Voted 10/10

That looks like it was a close shave! Glad no one was hurt!

Must have been a shocker when you guys realized you were standing on top of the same hazard!
Posted Nov 21, 2010 1:03 pm

splattskiRe: Hell!

splattski

Hasn't voted

It was. Sort of a Homer Simpson moment: "Doh!"
Posted Nov 24, 2010 4:43 pm

Bill KerrMoats

Bill Kerr

Voted 10/10

In the Mountaineering:Freedom of the Hills these gaps are called moats - page 342 in my version. They occur alongside big rocks or steep walls due to wind deposit variations or melting causing the snow to pull away from the rock. Melt water running over the rock can form really deadly versions (as noted by FortMental) as the ANAM (Accidents in NA Mountineering) have cases of people falling into these and drowning/suffocating in the Canadian rockies. Note this occurs on a smaller scale around most rocks which is an ankle break hazard.
There is a Euro word like Bergschrund for moats but can't remember it.
Seperate discussion is trapdoors caused by gaps in the rock that are perpendicular to the ridge. I was climbing a ridge and staying back from the cornice when I went up to the waist in such a gap- held myself with ice axe - when I crawled out I could see out the bottom where my one foot had broke through.

Posted Nov 21, 2010 2:38 pm

Dmitry PrussRandkluft

Dmitry Pruss

Voted 10/10

Randkluft is the European Alpinist term, but they are usually described as fissures separating the sides of the glaciers from the rock (as opposed to bergschrunds which are sort of behind the glaciers).
In spring, it doesn't have to be a cornice to create such a trap. In this picture, I got randklufted, sort of, in the middle of a slope:
Posted Nov 22, 2010 2:55 pm

splattskiRe: Randkluft

splattski

Hasn't voted

That looks like a similar deal. I like "randkluft"
But the machine translation to English comes up as "edge gap." Quite descriptive, but doesn't really convey the hazard.
Posted Nov 24, 2010 4:50 pm

Dmitry PrussRe: Randkluft

Dmitry Pruss

Voted 10/10

I think of "rim cleft".

Mechanistically, a bergschrund opens up because the ice slides away from the rock. A randkluft opens up because the ice melts away off the surface of the rock. At least that's how they taught me back in my undergrad years :)

The Germans are famous for their compound words ... but I got a feeling that the Eskimos may have a better word for "our" fav hazard.
Posted Nov 24, 2010 5:06 pm

mvidahoclimberThanks splattski

mvidahoclimber

Voted 10/10

Great article. Kinda freaked me out, but I learned a lot!
Rob W
Posted Nov 22, 2010 10:37 am

MoapaPkThanks

MoapaPk

Voted 10/10

We too (sort of like Fortmental) have problems near cliff bands and waterfalls. The snow will appear to be continuous up to the cliff band; but below, it is soft and may even have pulled way from the rock.
Posted Nov 22, 2010 2:22 pm

splattskiRe: Thanks

splattski

Hasn't voted

I *expect* a hole near an exposed rock. As you can see in the picture, this was a hole in a flat area of snow. Totally unexpected!
Posted Nov 24, 2010 4:52 pm

MoapaPkRe: Thanks

MoapaPk

Voted 10/10

I'm not talking about obvious cliff bands; there may be snow completely covering them. The only manifestation of the band may be a slight hump in the surface on a 30 degree-average slope. Later on in the spring, the tops melt out and become more obvious.
Posted Nov 25, 2010 8:28 pm

mtybumpoWow!

mtybumpo

Voted 10/10

I never would have thought of something like that! Where was this?
Posted Nov 22, 2010 2:37 pm

splattskiRe: Wow!

splattski

Hasn't voted

This was Peak 9290 in the Sawtooths. I'll get a page put up soon.
Posted Nov 24, 2010 4:42 pm

jwelSurprise!

jwel

Voted 10/10

I had a similar expereince while descending Mount St. Helens this past May. It also happened near a cornice around some rocks. I was not able to exit the hole until my climbing partner "Billisfree" removed my back pack. Another reason not to climb alone.
Posted Nov 22, 2010 7:39 pm

Sierra Ledge RatRandkluft

Sierra Ledge Rat

Hasn't voted

And then there is the randkluft, as noted above, which everyone erroneously calls a "bergschrund." Two separate entities, a randkluft and a bergschrund. Randkluft: gap between rock and ice. Bergschrund: crevasse between the glacier and the headwall ice. In Colorado I have experienced the “hmmpph” when skiing over clumps of bushes.
Posted Nov 22, 2010 8:17 pm

Grampahawkmoats

Grampahawk

Hasn't voted

I lost a hiking pole down a moat. I figure it's just another sacrifice to the mountain gods.
Posted Nov 23, 2010 5:13 pm

DharmaBum1984Tension Cracks

DharmaBum1984

Hasn't voted

Good article. Randkluft seem a close relative of tension cracks, which form when cornices grow from the top of vertical cliffs. The sheer weight of the cornice (instead of melting) pulls it out from the cliff, forming a crevasse hidden by a thin snow bridge. I fell into one of these in during a tour in the A-Basin backcountry (Chihuahua Bowl) 2 yrs ago. I dislocated a shoulder and couldn't climb out by myself. I could see over 20 feet down with my ski balanced on a bit of rock. Thought I was going for the ride. Scary stuff, glad my partners acted quickly and pulled me out.
Posted Nov 24, 2010 10:40 pm

Viewing: 1-19 of 19