by Neil Foote
Be it necessity or leisure, the snow hole is the most effective form of shelter within a winter mountain environment. Yet unlike woodland shelter, there has to be a lot more judgment and understanding of the building medium and topographical features to avoid an unpleasant, potentially dangerous experience. The snow hole has been essential to survival for many over the years - from indigenous communities; the famous Heroes of Telemark (who led a resistance against Nazi Germany in Norway); to present-day Alpine and Himalayan climbers.
The first thing to think about is location. Prevailing winds are typically South West in this country, causing wind-carried snow to lay deepest in the North East Lee slopes (this of course depends on the history of recent wind conditions). In Scotland, especially in the 2010/2011 season, the snow can lie for up to 10 metres deep, which is ideal for excavating a snow hole.
An avalanche probe should be utilised to test for any discrepancies within the snow pack, feeling for any excessively hard snow with wind slab (hard packed freshly blown snow) lying on top. An avalanche pit is also a useful tool to get an idea of the local stability within the different layers in the snow. A hidden layer of Graupel under slab can act as lubrication for any subsequent snow fall. Being avalanched whilst digging, or worse being buried whilst inside a snow hole is a real possibility.
Figure 1. A typical Lee slope with good snow build up
Temperature will dictate which style of snow hole is more relevant. In Scandinavia and the Arctic regions, a ‘Kaloo’ or traditional Norwegian set up is the preferred choice. The idea is to dig a corridor straight into the snow pack and leave raised sleeping platforms either side. This has two distinct advantages: The first being that it keeps you closer to the top of the cave where the warm air from body and stove rises. The second is, as the cold air drops to the floor , it is allowed to escape through the doorway, which is in line with or often lower than the sleeping platforms - in effect acting as a cold sink. The roof has to be perfectly smooth and rounded to support the weight of the snow being exerted from above and the sides. In warmer climates, the Kaloo is prone to collapse.
Figure 2 The beginning of a Kaloo
In the British mountains, where the ambient temperature rarely drops below -10° and is more than often in the -1° to -7° range, it is more important to try and hold onto some of this cold air to stop the inner surface melting and dripping onto you. In this case a snow cave may be more appropriate. This can be dug quickly by two or more people, starting a planned distance apart, two doorways are dug in unison and joined once inside. The sleeping spaces are on the floor which encourages the retention of the cold air and expulsion of any warm air quickly.
Once the snow hole has been dug, the doors can be capped from the top downwards by cutting blocks from above the chosen site and sliding them into place.
Figure 3. The Kaloo - note the heat sink at foot level
Believe it or not more people succumb to Carbon Monoxide poisoning than by the collapse of their snow hole. Carbon Monoxide is produced from using a gas or petrol stove in an enclosed space and is formed when there is not enough Oxygen to produce Carbon Dioxide. Two essentials are needed to counter this. The first is a small hole punched through the roof with a ski or walking pole to allow the Carbon Monoxide to escape (CO is slightly lighter than air). The pole is left in place to clear any spindrift that may accumulate during the night. The second is a candle, (apart from the obvious extinguishment of the flame telling you that there’s not enough oxygen for the flame to burn) which should be slightly flickering to confirm there is a small amount of air circulation throughout the sleeping space.
As we all know the mountainous regions of the world are amongst the harshest and unforgiving environments on the planet. The old adage of “there’s no such thing as bad weather, just bad equipment” holds true! Apart from having the usual ice-axe, crampons, water proofs, map, compass, weather reports and spare clothing, you should be equipped with an avalanche probe, snow shovel, bone saw, a good 4-season sleeping bag, a reliable stove and most important of all.... good quality training.
Neil Foote runs Backcountry Survival