An avalanche is any amount of snow sliding down a mountainside. It can be compared to a landslide, only with snow instead of earth. Another common term for avalanche is “snowslide”. As an avalanche becomes nearer to the bottom of the slope, it gains speed and power, this can cause even the smallest of snowslides to be a major disaster.
There are two common types of avalanches, a Surface Avalanche that occurs when a layer of snow with different properties slides over another layer of snow. For example: when a layer of dry loosely packed snow slides over a dense layer of wet snow. The other common avalanche is known as a Full-Depth Avalanche which, as it’s name would lead you to believe, occurs when an entire snow cover, from the earth to the surface, slides over the ground.
An avalanche can be composed of many different kinds of snow depending on the region, temperature and weather. It could be compiled of loosely packed light fluffy snow, which can still be very dangerous even though it may not appear threatening. It could also consist of a thick “slab” which is an area of tightly packed together snow that separates itself from the surroundings.
Why Do Avalanches Happen?
The snow packed down on the surface cannot support itself with all the weight. When another factor is introduced, such as a person’s step, this helps to loosen the snow and an avalanche occurs. Major temperature changes, rapid wind speed and man-made influences are the main causers of why avalanches occur.
Most avalanches begin within weak layers of snow, which evolve within the snowpack or form on top of the snow and become buried. Eventually these weak layers can no longer hold up the weight on the overlying snow, and will give way causing the snow above them to break free and slide downhill.
Where and When Avalanches Can Happen
Avalanches happen on mountains with extreme amounts of slow fall and build-up. Wherever snow is lying on ground on an extreme and sufficient angle there is potential for a sleeping avalanche. The steadily increasing numbers in popularity of winter activities along with the growth of interest in skiing has resulted in a much greater hazard. There are many sites around the world that are potential or have already experienced avalanches. Europe, France, Swiss mountains, Western Canada, Utah, Alaska, and Colorado are just a few places that have high probability of avalanches. All of these locations go through a thaw and freeze during the year at the bases of though mountains. This is very stressful on the snow built up above and packs it tighter together.
Three main factors effect whether or not avalanches are probable to occur. These three factors are the weather, the snow pack and the terrain. The weather is the most important when deciding whether avalanches are likely to happen. The height of the snow pack is dependent on the weather also. From the weather the temperature, wind speed and direction are the factors to watch. With a quick change in any of the weather factors an avalanche could is
