Mountain Skills: Understanding The Extended Column Test

I like to approach backcountry skiing like I approach a science experiment: I take time to plan before doing the experiment; I develop a hypothesis about what is going to happen when I perform my experiment; I conduct the experiment. And then I reflect on my experiment and learn from it.

Before heading out to travel in the backcountry, I do my planning. I check current conditions, read the avalanche hazard forecast, and plan a route appropriate for the conditions and for my partners that day. I go out into the field with a hypothesis about stability and about what the snowpack looks like.

While on tour, I like to test this hypothesis regarding the day’s conditions. A quick snowpit with a stability test or two is a great way to investigate the snowpack. After all, stability tests are a tool for evaluating the snowpack and testing the day’s stability hypothesis. I strive to dig several times during a tour, asking if there is a recipe for an avalanche—a slab, a weak layer, a bed surface and, if so, how reactive that recipe is to loading.

If I’m short on time or choose to do only one stability test, I use the Extended Column Test. The reason more and more professionals are turning to the Extended Column Test is because it’s a larger block test that shows fracture initiation and fracture propagation. This means that these tests, when done properly, can illustrate how reactive a weak layer is and, if that weak layer fails, how likely it is to propagate across a slope. It’s an avalanche on a very small scale.

How to do an ECT from American Avalanche Institute on Vimeo.

Here’s what to focus on when doing an Extended Column Test:


Don’t leave home without an opinion on current stability. You should have an idea of what the current avalanche problem(s) is, how widespread it is, where it is and how reactive this problem is. It’s important to have an opinion to test when traveling in the backcountry as this opinion can make you a more focused observer. When you dig in the snow, test this hypothesis. Is the avalanche problem the forecast center talked about present in your location? Often times, you don’t know unless you stick your shovel in the snow.


A good snow pit is safe, representative and polite. You don’t want to get avalanched while testing your snow stability hypothesis, so dig your pit in a safe area. Current research indicates that the Extended Column Test offers valid results on flat terrain, as well as on steeper slope angles. Make sure your pit site is representative of where you want to travel—similar aspect, similar elevation, similar exposure to wind or sun. And make it polite. No one wants to fall into a pit crater in the middle of the most popular backcountry run in the area.


The Extended Column Test is a 90cm wide column by 30cm upslope. It is isolated on all four sides. The column is then loaded from one side or the other in a series of taps that mirror the taps of a compression test: 10 taps from the wrist, 10 from the elbow, 10 from the shoulder. You are looking to see if a weak layer fails and, more importantly, if that failure travels across the entire column. Results are recorded as ECT, propagation (P) no propagation (N) or no result (X), number of taps (1-30)


Assessing stability is part science, part voodoo magic. Do everything in your power to use as much science as you can. This means cutting straight columns, focusing on accuracy and doing more than one stability test during the day. The more repeatable a result is, the more you should pay attention to that result. Write down what you find. Keep it in your records to build subsequent forecasts and remember to share it with the local forecast center.


People often skip stability tests, including the ECT, because they think it takes too long. After all, daylight hours are short in the early winter and no one wants to lose half an hour to pit digging. But performing an ECT and other tests don’t take very long if you know where your tools are in your pack, you dig efficiently and if it’s not the first stability test you’ve done this season. Just like transceiver skills and transitioning, the more practice you get, the better you will be. Efficiency is the key to almost every part of winter travel—incorporate that into your snowpits, as well.


The Extended Column Test is a popular stability test, allowing backcountry travelers to look at initiation (how much force it takes a weak layer to fail) and at propagation (how far the failure propagates across the column and, possibly, across the slope). The Extended Column Test is most effective with weak layers within the top 90 cm of the snowpack. If the weak layer is deeper than 90 cm, the ECT is not the best test for evaluating the weak layer. Tap on the thinner side of the column, if there is one, as research shows that fractures initiated in thinner snowpack are more likely to propagate into thicker snowpack than vice versa.

The Extended Column Test is not as effective when testing very soft snow—when you tap on the column, really soft snow crumbles.

Apply stability test results with a grain of salt—an unexpected propagation result should make you pay attention whereas an unexpected no-propagation result should make you suspicious of your test.


The Extended Column Test (or any small column test) offers information for the specific area where your pit has been dug. There can be variability in strength and failure across slopes. This is one of the reasons that digging more than one snowpit is recommended. The more quick pits dug during a day, the more information you have on the snowpack. Simply put, you have more data points on which to test your hypothesis.

Remember, bulls-eye clues such as cracking, collapsing, and avalanche activity trump stability test results. These clues are akin to Mother Nature screaming in your ear that instability exists.


Interpreting data from snowpits can be confusing and overwhelming. If there is any confusion, choose to travel in simpler terrain—choose a lower angle line. Good terrain selection is key for backcountry travelers.

Sarah Carpenter is the co-owner of the American Avalanche Institute and an AMGA-certified ski guide. Her first job out of college was ski patrolling at Bridger Bowl, Mont., and she’s been working in the snow and avalanche industry ever since as a patroller, ski guide and avalanche educator.


  1. […] polymer) probes are stiffer – they don’t flex as much. When you’re building a pit for an extended column test (ECT), you use two probes and a cornice saw to cut out the back of the column. Carbon probes are nice for […]

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