An avalanche is an event that occurs when a cohesive slab of snow lying upon a weaker layer of snow fractures and slides down a steep slope. Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack. After initiation, avalanches usually accelerate rapidly and grow in mass and volume as they entrain more snow.
About Avalanche in brief
An avalanche is an event that occurs when a cohesive slab of snow lying upon a weaker layer of snow fractures and slides down a steep slope. Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack. After initiation, avalanches usually accelerate rapidly and grow in mass and volume as they entrain more snow. If the avalanche moves fast enough, some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current. Slab avalanches form frequently in snow that has been deposited, oreposited by wind or snow. They have the characteristic appearance of a block of snow cut out of its surroundings by a slab of ice. The largest avalanches or suspended currents form known as powder snow avalanches. These consist of a cloud of snow that was entrained in the avalanche on the snow that remained on the slope that remained that remained. Slabs can vary in thickness from a few centimetres to three metres and can be up to a metre in thickness. The majority of avalanche fatalities in backcountry users are backcountry avalanche-related. Backcountry avalanche fatalities account for 90% of avalanche- related fatalities in the backcountry. Most avalanches occur spontaneously during storms under increased load due to snowfall andor erosion. Other natural causes include rain, earthquakes, rockfall and icefall. Artificial triggers of avalanches include skiers, snowmobiles, and controlled explosive work. Contrary to popular belief, avalanche are not triggered by loud sound; the pressure from sound is orders of magnitude too small to trigger an avalanche.
A snowpack will fail when the load exceeds the strength. The strength of a snowpack is much more difficult to determine and is extremely heterogeneous. It varies in detail with properties of snow grains, size, density, morphology, temperature, water content; and the properties of the bonds between the grains. These properties may all metamorphose in time according to the local humidity, water vapour flux, temperature and heat flux. One of the aims of avalanche research is to develop and validate computer models that can describe the evolution of the seasonal snowpack over time. The second largest cause of natural avalanches is metamorphic changes in theSnowpack such as melting due to solar radiation. The top of theSnow pack is also extensively influenced by incoming radiation and the local air flow. Other natural Causes of Avalanches include wind by wind, rain by rain, and snowfall by icefall and erosion by glacier movements. The most common time for avalanches to occur is in winter or spring but glacier movements may cause ice and snow avalanche at any time of year. A large volume of snow, that may be thousands of cubic meters, can start moving almost simultaneously, so that a largevolume of snow can startmoving almost simultaneously. The avalanche can be described by their size, their destructive potential, their initiation mechanism, their composition and their dynamics. Large avalanches have the capability to entrain ice, rocks, trees, and other surficial material.