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How to assess crevasses and undermined snow??

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  • How to assess crevasses and undermined snow??

    I made my first trip to Tuckerman last week, and although I have been reading the Avalanche Center website religiously, I feel relatively ignorant of the hazards of crevasses and undermined snow.

    I saw several cracks in HH and the left gully when I went and wondered if those were crevasses opening up. However, the boot ladder and everyone else present just walked right over them (so I did to...). If those were the makings of a crevasse, how does one determine that they are still safe to walk on?

    Undermined snow- is there any way to spot this?

    Specific question about GoS-
    It sounded as though the entire bottom section (right as you emerge from the trees/brush) is on top of running water. Does anyone know how deep it generally is there? As in, if you punch through, will you just be a bit soggy or is it a serious concern?

    Thanks for any light you can shine on this topic. Next time I'd rather not just blindly follow the bootprints of others who may not know any more than I do!

  • #2
    For crevasses, I would worry about the center headwall through Sluice much more than I would worry about left gully / hillmans.

    Understand that if it weren't for the large depths of windloaded snow that the Ravine receives all winter, the Lip and Center Headwall would be cliffs. The same is not true of Left/Hillmans.

    Crevasses get huge under the Lip. Deeper snow (60 feet!) means deeper crevasses.

    And then there is the waterfall hole.


    • #3
      Having just been up to GoS a few days back, I would peg the base depth at the runout of the Main Gully at 2-4 feet. You could hear water running below at spots during the climb up the actual gully, but it was not loud & sounding like a river or anything like that), and down below at the base there was no sound. Further down where the trail begins, the water running was not significant (and that was in real warm weather), like a few inches deep. I do not think there is a significant drainage running below the Main Gully or top of the trail.

      Now, nearby is the main drainage for the Gulf, the New River, and that probably has much more water running in it, with perhaps some snow bridges in spot near the top, but it's not like you could easily end up in there accidently from the GoST... In fact, I don't think it would be too easy at all to head more to Looker's Left of the Main Gully, due to the weak snow and lots of little tree traps (mid-Winter there is much more snow in the base of the gulf to allow you to traverse out along the base of the headwall more easily in either direction to the other Gullies). There are also a couple feeder drainages that you cross which come down from the Boot Spur/Finger Gullies that could have a couple feet of water running in them, when melting is going on, just before reaching the Main Gully, and eventually those snow bridges there could collapse from yoir weight and get you wet, or maybe worse. Most of that risk is now mitigated by the freeze, and even wif it does gets real warm again, I would think that there is just a lot less snow up there left over from the recent thaw to melt and get the water running too heavily again (but more snow could change that...).

      As I understand it, other than falling & possibly getting injuries there, the big concern with undermining is that you could be standing over a heavy volume of swift water, and this could carry you under snow or pin you in a position that could trap & drown you. In spots like the Little Headwall, or further down in the Cutler River -drainage just below HoJo's, having the snow collapse under you could have dire consequences. If you have ever been in Tux during a warm Spring melt and seen the heavy water running as you near HoJo's, you would know that falling in there would be real bad news... :{

      These heavier water flow spots are generally the same spots identified on the maps by blue lines, as they are large enough drainages as to have water year-round (with the amount of water during Spring Melt generally the most water running down them... and real cold water, too). Another example of a place on MW that gets traffic, but which could have some more serious undermining risks would be Monroe Brook. Best practice I think for when you may be skiing/riding in such a location is to keep ears peeled (maybe forget the tunes, if you like them for the downs), and if you saw/heard water on the climb/descent, try to stick closer to the edges of the brook/river, giving you better odds of not falling through, and improving your chances to get out/be helped, should the snow collapse. Obviously, on a real warm day, when you can hear the water rushing below, it might just be better to get out of the drainage completely and not push your luck.
      Last edited by petebanta; 03-27-2012, 11:43 AM.