A pit dug vertically into the snowpack where snow layering is observed and stability tests may be performed. Also called a snow profile.
Some of the time we can gather enough information about the snowpack without ever taking out the dreaded shovel. But often the only way to get good information is to dig. At least one snowpit in a representative location helps to at least get the general picture of what’s going on in the snowpack.
How to dig a snowpit:
Contrary to popular belief, snowpits don’t have to take a lot of time. My philosophy is that if your feet get cold, you’re doing something wrong; I almost never spend more than 10 minutes in a snowpit. Since snow can sometimes vary quite a bit from place to place, I would much rather dig several quick pits and average the results than to spend 30 minutes in one pit documenting every useless detail. We’re trying to get a GENERAL, BIG PICTURE idea of what’s going on here. Then move on to another location. Often I dig the hole without even taking off my skis or board, but it usually helps to at least take off the uphill ski or take one foot out of the board binding.
First, the shoveling: Get down on one knee when you shovel. Your back will thank you, and especially if you grew up Catholic, like me, it somehow feels appropriate to get on your knees when asking for answers from the unknown. Make the hole wide–about the width of a ski length. And don’t dig a vertical hole, like you’re going to China, shovel out the downhill side so you have room to work, which actually takes less time in the long run. Just slide the chunks of snow downhill on your shovel without lifting it. This only takes a couple minutes if you’re on a steep slope and in soft snow.
Then get your tools ready. Get out the snow saw. If you don’t have one, than go buy one. You can get by without one but you will hate life and hate snowpits and you will quickly quit digging them. Not a good idea. If you’re a skier, get a snow saw that fits on the end of a ski pole.
After digging the snow pit (which gives you a lot of information in itself) I like to just dive in and FEEL with my hands. Some people like to use a little whisk broom and gently brush the wall, but don’t listen to them. Run your mittens horizontally across the face of the snowpit wall and get a nice tactile feel for the different layers. Just like an eroded rock outcropping, notice how the weak layers crumble away while the strong layers remain sticking out. Then stand back and SEE the layers too. Dive in and get your hands dirty. Remember that this is not just an academic exercise. This is your life we’re talking about here. Just looking and thinking don’t work. Crawl around, shove your arms into the weak layers. Feel it, see it, chew on it, smell it–live it. Use as many pathways as possible–BE the snowpack, as they say.
Then dust yourself off (if you’re not getting snow on you, you’re doing something wrong) and carefully smooth the snowpit wall in preparation for the various stress tests you will perform. Make sure it’s smooth and vertical. This is very important. Remember, garbage in–garbage out. But good tests will give good answers. Whatever tests you do, they must be done exactly the same each time, so that one can compare one snowpack to another.
How deep to dig a snowpit:
Since it’s difficult for humans to trigger avalanches more than about 1.5 meters (5 feet) thick, (unless they are triggered from a shallower spot) I seldom dig snowpits deeper unless I specifically know there’s a deeper weak-layer that may cause problems. If you already know that the deep layers have no worries, then just concentrate on the shallow snow. Each situation is a little different and in time you will get a feel for it. But in general, keep your snowpits less than 1.5 to 2 meters deep unless you know of a good reason to go deeper.
Where to dig a snowpit:
Where to dig a snowpit is probably more important than how to dig one. Choosing a representative location is an art, and art is difficult to describe.
Dig it on a slope most representative of the slope you are interested in but without putting yourself in danger. Often you can find a small representative test-slope–one that won’t kill you if it does slide. Or, you can work your way into progressively more dangerous terrain. For instance, if a snowpit on safe terrain gives you a green light, then it gives you the confidence to dig another one on more dangerous terrain. Green light there? Then, move onto even more dangerous terrain, and so on. Never dive into the middle of a dangerous avalanche path without first gathering lots of additional data about the stability of the slope.
Don’t dig it along ridgelines where the wind has affected the snow–a common mistake. Although sometimes the crown face of an avalanche may break right up to the ridge, the place where we most often trigger avalanches is 100 or more feet (30 meters) down off the ridge. Avoid thick trees because conditions are often quite different than on open slopes. Avoid compression zones and tension zones. Avoid places where people have compacted the snow.
LOOK FOR NEUTRAL, OPEN AREAS AT MID SLOPE WITHOUT WIND EFFECTS.
Use an avalanche probe to find a representative place with average depth. Poking around with a probe can save a lot of time digging in stupid places, like on top of a rock or tree or where a previous party had their lunch.
Most important, dig lots of snowpits in lots of different areas because the snow can vary quite a bit from place to place. Look for the pattern of instability.
Simple Snowpit Tests:
For simple snowpit tests you do not need to be in steep terrain. Recent research shows that slope angles of 25 degrees are sufficient and even gentler slopes will still provide good data. This means you do NOT have to exposure yourself to avalanche danger to collect stability data. If at all possible, use a snow saw because it makes your test go much faster.
Some of the more common tests used include the Extended Column Test and the Compression Test. It’s best to take a class or get a mentor to show you how to do these tests, and – more importantly – how to interpret them.