Avalanches can happen wherever there is snow, lying on ground of sufficient angle. The growing popularity of winter climbing, hillwalking, ski-touring and off-piste ski-ing means greater numbers of people are at risk. Each year there are accidents and fatalities and many of these would have been avoided with greater care or knowledge, or if the victims had even paused to consider that avalanche hazard might be present.
What is an avalanche? Snow is deposited in successive layers as winter progresses. These layers may have dissimilar physical properties and an avalanche occurs when one layer slides on another (surface avalanche) or where the whole snow cover slides on the ground (full-depth avalanche). It may be loose snow, when it starts at a single point, or a slab avalanche which occurs when an area of more cohesive snow separates from the surrounding snow and slides out.
Before you set out, it is vital you check the snow and avalanche reports where available. These are issued every day from mid-December to mid-April for Glencoe (including Glen Coe and Glen Etive hills), Lochaber (inc Ben Nevis and Aonach Mor), Northern Cairngorms (inc Northern Corries and Loch Avon basin), Southern Cairngorms (inc Lochnagar and Glen Shee) and Creag Meagaidh (inc north Laggan hills westward to Beinn a'Chaoruinn). Avalanche information is also available in the Internet, local radio and newspapers. Sources are listed at the end of this article.
When you're out in the winter, first look out for visible avalanche actvity. If you see avalanche activity on a slope where you intend to go, go somewhere else.
Look out too for new snow build-up. More than 2cm an hour may produce unstable conditions and more than 30cm continuous build-up is regarded as very harardous.
Watch out for a lack of continuity between layers, slabs lying on ice and sudden temperature rises. Importantly, if it feels unsafe retreat.
Many avalanches are cornice-triggered. In general, climbing below cornices should be avoided during snowstorms or heavy drifting and up to 48 hours afterwards, and during heavy thaw or sudden temperature rise.
On most hills in the UK, avalanche hazard can be avoided completely by a sensible choice of route. Most large slab avalanches run on slopes between 25 and 45 degrees. Convex slopes are generally more hazardous than uniform or concave slopes and ridges or buttresses are better choices than open slopes and gullies. Lee slopes should be avoided after storms or heavy drifting.
It is rarely essential to negotiate an avalanche-prone slope. It is usually possible to find another way, or back-off. And it's worth considering the fact that 90% of avalanches involving people are triggered by their victims.
* Solo travellers in avalanche terrain are in particular danger.
* Off-piste skiers face the greatest danger. The lateral cutting action of skis readily releases unstable snow.
* Direct descent or ascent is safer than traversing.
* If in a group, go one at a time. The others should closely observe progress.
* Close up clothing and wrap a scarf or similar item round the nose and mouth.
* Belay if possible, although this is rarely feasible on wide, open slopes.
* Try to delay your slide by plunging an ice-axe into the undersurface. This may help keep you close to the top of the slide.
* Shout. Others may see you.
* Try to run to the side, or jump up-slope above the fracture.
* If hard slab, try to remain on top of a block.
* Shed gear, sacks, skis, etc.
* Try to roll like a log off the debris.
* Swimming motions sometimes help.
* As the avalanche slows down, you may be able to get some purchase on the debris. Make a desperate effort to get to the surface, or at least to get a hand through.
* Keep one hand in front of your face and try to clear/maintain an air space.
* Try to maintain space for chest expansion by taking and holding a deep breath.
* Try to avoid panic - this could waste vital energy reserves. If you are walking with friends, they are probably search for you.
* Observe the victims progress and, if possible, mark the point of entry and point at which the person was last seeen.
* Check for further avalanche danger.
* Make a quick search of the debris surface. Look for any signs of the victim, listen for any sounds and probe the most likely burial spots.
* Make a systematic search, probing the debris with axes or poles.
* Send for help.
* Keep searching until help arrives.
* Remember you are the buried victim's only real chance of being rescued alivel. Although survival chances decline rapidly with duration of burial, they don't reach zero for a long time.
Scottish Avalanche Information Service website at www.sais.gov.uk
National and regional newspapers in Scotland.
Local radio, particularly Nevis Radio and Speysound.
Reports are posted daily on strategic noticeboards in the five areas listed, usually in the main car parks.
The Scottish Avalanche Information Service keeps records of avalanches throughout the UK. They are always keen to hear from anyone who has witnessed an avalanche. Recording forms are available from SAIS Co-ordinator, Freepost, Glenmore Lodge, Aviemore, PH22 1BR or call the SAIS/Nevisport reports hotline (free) on 0800 0960 007.
Acknowledgement: Information contained in this article is sourced from the Mountaineering Council of Scotland.