Avalanche
- How does avalanche form?
- Deaths caused by avalanches
- Avalanche prevention

The most devastating after- effects of snowstorms are avalanches. These occur when snow builds up on slopes and then falls without warning. On gentle slopes there is not enough gradient to make the snow falls downhill, and on very steep slopes the snow cannot build up enough to pose a threat. But avalanches are a real danger on slopes that are at an angle of 25 to 40 degrees. With up to a million tonnes of snow hurtling down a slope at speeds of over 320 km/h, an avalanche can rush everything in its path.

Deaths caused by avalanches

Avalanches are very common- there are about 100, 000 each year in the American Rockies alone- but most are in uninhabited areas and are no danger to people. However, as skiing and snowboarding become more popular, more and more people are living, working and spending holidays in areas threatened by avalanches.

>> Houses in the small Italian village of Morgex were reduced to rubble by an avalanche on 23 February 1999.

Deaths in avalanched are caused in three main ways.
1. It is by the crushing force of the avalanche, especially as the hurtling snow picks up debris, including boulders, rock and soil, as it falls.
2. People who are buried underneath the snow can quickly suffocate.
3. The intense cold which causes hypothermia and then death.

Avalanches Prevention

Usually avalanches can be controlled by setting up barriers and using explosives to set off small avalanches before the snow can build up too much. This technique is used at all ski resorts and in other high- risk areas. However, on this occasion the snowfall was extremely sudden and heavy in areas that are not usually at risk from avalanches, so little could be done in advance to prevent the disaster. The number of people killed was only a small percentage of those in the area at the time, which shows that people living and holidaying there are generally well- protected.
>> Various methods are used to prevent snow from building up and to try to reduce the impact of any avalanches that do occur.

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