Uphill Snow Anchor for Crevasse Crossing?


Original Post
Chris C. · · Seattle, WA · Joined Mar 2016 · Points: 91

I'm wondering what is seen to be as the best method of protecting a moderately uphill crevasse crossing.  I've seen a lot of people just bang pickets in perpendicular to the slope, clip through, and cross. (That's what I have always done as well.)  However, it seems that in a steeper situation, falling into the crevasse could potentially pull the anchor up and out of the snow.  A t-slot seems like it could suffer from this issue as well.  

Is this in reality a non-issue?

Petzl has a bit of info published about crossing a steep bergschrund.  However, going into a full lead climbing belay setup seems like an overkill for many situations where you may want to just use a running belay.

https://www.petzl.com/US/en/Sport/Crossing-a-bergschrund-on-a-snow-slope?ActivityName=Mountaineering#.WRoLUvnysdU

Thanks all!

Nick Drake · · Newcastle, WA · Joined Jan 2015 · Points: 438

Not a direct answer to your question, but some very good food for thought:

http://arc.lib.montana.edu/snow-science/objects/ISSW_O-061.pdf

Last year while skiing Baker early season with thin snow cover over crevasses my partner had a ski take off from the Squak down into the Easton. I made a sturdy dead man with a 24" smc picket and had her belay me with two biners on an atc. Should have used an avy probe to check for crevasses instead of an axe...long story short I took a whip. Ripped 115lb belayer right out of the trenched out stance she had kicked and put us both on the anchor. In real life consider any snow bridge failure will likely have as much force as your hardest lead fall, plan accordingly. I thought about the times we have done a boot axe belay before in the past and shuddered. 

curt86iroc · · Golden, CO · Joined Dec 2014 · Points: 3
Chris C. wrote:

I'm wondering what is seen to be as the best method of protecting a moderately uphill crevasse crossing.  I've seen a lot of people just bang pickets in perpendicular to the slope, clip through, and cross. (That's what I have always done as well.)  However, it seems that in a steeper situation, falling into the crevasse could potentially pull the anchor up and out of the snow.  A t-slot seems like it could suffer from this issue as well.  

Is this in reality a non-issue?

Petzl has a bit of info published about crossing a steep bergschrund.  However, going into a full lead climbing belay setup seems like an overkill for many situations where you may want to just use a running belay.

https://www.petzl.com/US/en/Sport/Crossing-a-bergschrund-on-a-snow-slope?ActivityName=Mountaineering#.WRoLUvnysdU

Thanks all!

FYI - Vertical pickets should never be placed perpendicular to the surface.  To resist a downward pull, you actually want to picket angled back about approx. 15deg or so.  This reduces the magnitude of the upward component of force.  

In the situation you described above, i would suggest a picket in a well constructed T-slot should do the job just fine (add vertical pickets to the T if you're concerned).  As with a lot of snow anchors, if having a single anchor point makes you feel uneasy, make a 2nd or a 3rd.  Also, be mindful of the snow you are placing the anchor in.

Guideline #1: Don't be a jerk.

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