A strong, simple and fast snow anchor
Disclaimer: There is WIDE variability in the strength of snow anchors, due to factors like depth of the anchor, what you’re using for the deadman, temperature and water content of the snow, whether you stomp down (aka work harden) the snow between the anchor and the load, etc. A certain snow anchor flavor that tests to a certain strength in one location does not mean that result applies everywhere.
If you carry a picket, you have various options for building a snow anchor. With a very hard snow you can maybe use a vertical picket top clipped. With medium to hard snow, a vertical mid clip picket can work.
However, with softer snow, or if you choose not to carry a picket, about your only option is the “T slot” (aka deadman) anchor. This anchor can be made with gear like an buried ice axe, skis, or a backpack.
Here’s a way to (maybe?) double the strength of the T slot anchor, with a few seconds of work and one additional piece of gear: Add a vertical reinforcing placement to the horizontal placement.
image (used with permission) : https://www.vdiffclimbing.com/glacier-travel-snow-anchors/
This does a couple of good things:
It makes the horizontal placement much harder to pull out.
If the horizontal placement, like an ice axe, shifts a little bit under load, it can prevent the clove hitch (that's on the horizontal axe) from slipping.
(If you use a picket and girth hitch the middle hole for the horizontal piece, you don't have to worry about the connection point slipping.)
The typical method to beef up a snow anchor is to build an entirely separate one, and try to connect / equalize them with cord. This is certainly effective, but it can take a lot more time and gear (more cord and carabiners) to build, and will probably end up pretty much the same strength as this one.
Sounds good. How strong is it?
My pal Ryan Jenks at HowNOT2.com tested this. He got about 8 kN, which is pretty impressive! Compare this to a single horizontal buried picket, which he tested at about 4 kN.
Adding the vertical picket to reinforce the horizontal one pretty much doubled the strength of the anchor, at least in this one test.
Keep in mind this was in high water content snow in the Washington Cascades. This usually conpacts very well and make some reasonably strong anchors. Your mileage may vary.
Keep in mind that a typical crevasse rescue anchor will only need to hold less than the weight of the victim when they’re hanging. (The friction of the rope passing through the snow reduces the load on the anchor.) When hauling with a 2:1, if the pull strand is not redirected, the anchor should see about 2–3 kN at most. So, in the typical crevasse rescue scenario, loads on the anchor usually are fairly low which is a good thing.
I’ve seen quite a few studies of the strength of horizontal deadman anchors, but this is the only one that adds the vertical element. If anyone knows of other studies, please email me; I’d like to add those to this article.
Cut to the action: horizontal picket about 6:00. Reinforced horizontal picket, about 6:45
Screen grab from the above video, setting up the reinforced picket.
Finally, for a very deep dive into snow anchors, here is a nice presentation from the Mountain Rescue Association featuring snow anchor expert Art Fortini.