Extended Column Test - How to interpret?

Great stuff Chris, thanks for posting it -- those are amazing test results.

I never made the assertion that the ECT was a "good way" but as this video shows, it can be revealing and " useful "for these sort of conditions. I was surprised by how well it worked in the video and that was my point and question.

What test, other than a deep tap test would be a "good way" to test for deep instabilities?

Well, I think the rutschblock test (I know it's now out of vogue) more directly answers the question currently relevant in UT: 'Is a skier likely to trigger this weak layer?" I would use ECT to test whether or not a failure would propagate. In the UT vids propagation is fast and smooth, but they have to whack the column pretty good to get it to move, so I'm not sure these ECT's are giving a lot of info on the ability of a skier to trigger the instability. They do point out the likely consequences of triggering.

If you remember last year and our MLK layer that got very deep, and then revealed itself in some huge( ANFO assisted ) slides last year at Crystal......one of the  hot topics for discussion last season between my BC buddies was how well that layer was bridged and how to test for it so deep down. Some never trusted it and stayed off the big stuff all year...others continued to test the top 4ft with CT's and hand shears and "hoped" the MLK was sufficiently bridged and skied the bigger stuff if this relatively "shallow" layer showed a good result in line with observed stability( no naturals, good temps  etc,)

Even though forecasters can spell out a deep PWL in their forecasts....the question of "is it deep enough to be bridged" seems to be causing a lot of the troubles in UT at the moment amongst the avid. The concept of deep enough to be bridged seems a fallacy in UT at the moment as the video and their "tall" ECT shows.

I would side with the folks that were staying off the bigger stuff, because I would not want to trust any determination of 'bridging' unless it was really conclusive that the bridging was far stronger than skier generated forces. And, as Cookie points out above, I certainly wouldn't trust any determination of bridging if other skiers were triggering the weak layer (as has been happening in UT, sadly). But I am very conservative.

Great stuff Chris, thanks for posting it -- those are amazing test results.

Thanks Marcus!
Seeing these videos has made me think about how avy information is presented.
We are certainly entering an age due to FB, GoPros etc where videos are overtaking the written word for our younger generation( whether good or bad.I don't know .......but it's a fact)

The avy organizations do a great job in communicating but its' my opinion that a video of an ECT column failing at 20 blows with a very quick and defined propagation does far more in explaining the danger level than a simple written ECT 20, Q1 at 1.55 M.

You need both but I would certainly  encourage avy organisations like NWAC to include more videos of the tests they are doing especially regarding these PWL's.
People supplying test results to their data sites, whether amateur or pros should be encouraged to video their pits and tests.
Seeing these results is very powerful communication.
Just food for thought.

The AIARE video on the ECT:
vimeo.com/32916718

Karl Birkeland ECT video...

Karl Birkeland ECT video...

Great video. Thanks.

There's been talk of how to interpret ECT results, and I like the way Karl phrases his analysis in this video. How conducive conditions are to fractures propagating is great information. Especially if you base travel decisions on some version of the likelihood versus consequences spectrum that Martin talked about a few years ago at the Avalanche Summit.