11 January 2019 from Danielle in 'General'' | 0 Comments

When you see a closed-off piste or an out-of-bounds sign, it’s an indication that the ski resort has judged the area unsafe for skiing. Far from trying to be killjoys, ski resorts occasionally close off terrain for skiers’ and snowboarders’ safety. Although there have been cases in which ski resorts were found not liable for injuries or deaths due to avalanches that occurred in-bounds in their ski areas, they still have a pretty big incentive to secure their in-bounds terrain and ensure the avalanche danger is next to zero. We’ve all seen the consequences when unlucky people venture out-of-bounds despite an avalanche warning. But just how does a ski resort decide what’s safe and what’s not safe for skiing and snowboarding?

Avalanches happen when the snow pack is unstable. They are often triggered by a skier or snowboarder putting weight on the snow pack as they move through, causing it to detach from the base underneath and send the top layer of snow hurtling down the mountain. As such, one easy way to anticipate a risk of an avalanche is when a lot of snow falls very quickly. The new snow is heavy – which disrupts the snowpack – and it hasn’t had time to bond securely to the layers underneath, making it unstable and ripe for an avalanche.

Analysing the snow pack: Snow quality

The next step in analysing avalanche risk is measuring the quality of the snow. Some ski resorts use a Ziploc bag to collect a sample of snow, which they then melt and weigh in a laboratory. Heavier snow bonds better to the snowpack, which means the avalanche risk is less – except in cases where a lot of snow has fallen in a short time span, as explained above. The snow safety team will also measure the temperature of the snow as a guide to know what kind of snow crystals will have formed. Different kinds of crystals will either bond together or splinter.

Analysing the snow pack: Snow layers

Next, the team will choose an appropriate (read: safe) spot, dig a hole and analyse the different layers of the snow pack wall. They’re looking to see how stable each layer appears to be, and they may use a tongue depressor or something similar to feel their way around and judge the composition of the snow in each layer. The team will also try to look at the edges of some of the snowflakes. If they’re splintering, it means they are older and the layers of snow are settling already.

Testing snow density

Controlled explosions

You might have seen the vestiges of avalanche explosives littered around the ski area (if so, don’t touch them!). Avalanche blasting is frequently carried out by ski resorts in an attempt to stabilise the snow pack. They will trigger controlled avalanches in order to get rid of some of the extra snow and make the rest more uniform and better-bonded.

European Avalanche Risk Scale: What do the numbers mean?

Although the 1-5 rating scale seems fairly straightforward, it helps to understand exactly what the numbers refer to:

1: Snow pack is well-bonded in most places
2: Snow pack is generally well-bonded except perhaps on very steep slopes
3: Snow pack is only moderately bonded on many steep slopes
4: Snow pack is weakly bonded on most steep slopes
5: Snow pack is generally unstable

A surprisingly high number of deaths by avalanche occur when the avalanche danger is stated as 3. Skiers and snowboarders should remember that an avalanche risk rating of 3 means that the snow pack in a good percentage of steep slopes may only be moderately bonded. People tend to underestimate this risk.

The information in this post is for interest only and should by no means be used in place of an avalanche course. Before venturing off-piste, always have the appropriate knowledge and be properly equipped. Hire a guide if you don't know the area

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Born and raised in the ski paradise of Vancouver, Canada, I learned to ski before I can remember, balancing precariously on my parents’ skis as they sailed down the hill. I started snowboarding in my teens and am now delighted to be exploring everything Europe’s ski scene has to offer!

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