Last weekend I got near the top of an ice climb and topping out required climbing a freestanding pillar of ice. In this case it was thick enough that I couldn't wrap my arms around it, maybe 1.5m wide and 0.5m deep, only fully detached from the wall for a couple of metres, and very well attached with good ice at the base and the top. So it seemed pretty safe to climb, but nevertheless felt very hollow when swinging the tools into it.
I realised I have no heuristics for assessing such structures. What do you use? The size? The quality of ice? The feel/sound when swinging? I guess all these things! Is there a difference about when you would climb something versus when you would put screws in it?
I'm not talking about free-hanging icicles here, just pillars which touch the ground.
What - like this?
I have never climbed anything I would call a proper ice pillar. but this is an interesting question.
I guess given you were topping out on a route you'd have the knowledge of conditions from the previous pitches which would be the best indicator of stability on the day. walking straight up to one of these things and pulling on must take a huge amount of confidence.
Yeah I've seen these and they're both scary. In both cases the "pillar" barely touches the ground and is certainly thinner at the bottom than the top, whereas all the ones I've seen people climb are wider at the base than the main part of the pillar.
Done some columns and curtains:
Sound, feel of the ice and the conditions over the past few days along with temperature on the day, running water, and finally sun!
Think there's a chapter or section on this in Will Gadds book:
Closest I have knowingly come to mishap is abbing down, off the big thing with air behind it, to land on the ice 'talus' slope beneath it. I was putting an ice screw in for the next belay and a big crack shot off left and right. You never saw someone scamper up a bit so fast and try again.
I've climbed a few similar sounding ones - maybe even a big bigger from the one you describe - when I lived in Finland. This for example https://1.bp.blogspot.com/-J7lAd48ciPs/T0AU9uDRJXI/AAAAAAAAFY4/tjnot63xxl4/s1600/DSC_0012.JPG the free standing bit is probably four body lengths long - so 7-8 mtrs. Not being strong at all on vertical ice, even using wrist loops, I have always found them utterly terrifying. I know on vertical ice (except for in exceptionally user-friendly conditions) I light the fuse as soon as I pull on to the vertical and its a short fuse before I completely pump out and it all goes bad quickly! I think the quality of ice on smaller free standing things is all important - fortunately on smaller features, not wobbly 25 metre pure free standing monsters, you can see how its attached at the top. I'm aware that although I've been lucky enough to climb more pure ice than most British climbers, I got to know and understand the conditions and the nature of the ice in the specific places I climbed predominantly in southern Finland. I climbed a reasonable amount up in arctic Norway and that felt really different again, and having climbed in England Wales and Scotland since coming back to the UK, the ice is again different here - sometime subtly, sometimes obviously.
I wouldn't kid myself that there are easy rules of thumb on judging the safety of such things - I really reckon it can only come with experience and big dose of luck!
From experience I have found ice pillars to vary depending on what forms them. A frozen stream running over a cliff will likely form a more hollow cylinder than a pillar formed from seepage, runoff or melt. Of course this may not be obvious from below.
Ice formed from slow seepage over time will initially form a dagger and an amalgamation of organpipes which in theory would be more stable and thus easier to protect, but may not get very big. Both streams and seepage pillars build as ice stalactites and stalagmites until they meet in the middle to form a pillar. Streams will normally have a big cone of cauliflower ice at the bottom. Streams are also more likely to have wild ice structures such as jellyfish as well as wind formed features such as cobras and big umbrellas.
Its not uncommon to reach the top of a pillar on a stream and find a glass like window of ice with water running behind giving you a view into the deep black abyss you have unknowingly climbed the front of.
With assessing such features I normally look for nice blue ice, anything white or grey is likely thin, aerated and possibly sun baked. Fresh chandeliers and small amounts of water will help indicate if the ice is still growing. Smooth rounded surfaces and smooth depressions will indicate sublimation of the ice. Hollow sounds are unnerving and will indicate thin ice. Of course recent weather and temperatures are key to understanding stability of pillars and petzl has a nice simple overview on this: https://www.petzl.com/US/en/Sport/Waterfall-ice-study?ActivityName=Ice-climbing
With protecting something like this, a solid screw in thick and consolidated ice at the base is best starting point (Although often most people will build a belay behind big pillars, in the EU there may even be bolts). Otherwise, you can often find very solid ice in a flat platform behind the pillar, which can take a long screw and an extender. If the pillar is short and you are confident you can gun the face and protect the top out by placing a screw in the ice above where the pillar meets the rock. The more solid the pillar sounds (subjective), the better its likelihood to take screws. Screamers can add piece of mind for screws in the pillar itself.
Personally hollow sounding pillars terrify me, tho this may derive from some Senja induced ptsd when one discovers the pillar isnt actually a pillar and rather the stumpy remains of one.
This Winter Conditions page gives a summary of what is being climbed at the moment, what is 'in' nick and what the prospects are...