Avalanches: Questions & Answers

Avalanche are a kind of high velocity mass wasting event in which the material fall down a mountain side due to gravity. If the material is mostly snow { Along with ice and associated debris such as rock fragments, soil and vegetation}, it is called snow-avalanche. Avalanches are natural disasters, hard to predict and hard to mitigate. Here are a few basic questions and their answers about avalanches:

What are the most snow-avalanche prone mountain regions of World?

Most snow-avalanche prone areas in the world include the higher mountain ranges of the world viz. Himalayas, Andes and high peaks of Yukon and Alaska etc.

What are sluffs and slab avalanches?

Snow avalanches can be divided into two major types viz.  sluffs and slabs. Sluffs {also called Loose snow avalanches} is basically a flow of small slide of dry, powdery snow as a formless mass. Sluffs occur in large numbers but are less dangerous in comparison to slab snow avalanches which encompass a kilometre or more in length with millions of tons of snow. Slab avalanches occur less frequently but are more dangerous.

How avalanche is formed?

The formation of an avalanche needs a slope shallow enough for snow to accumulate but steep enough for the accumulated snow to accelerate once set in motion by combination of loosening of snowpack (mechanical failure) and gravity (steepness, terrain, orientation of slope). The slope and angle of repose are important for avalanche formation.

Further, the snuffs and slab avalanche form in different way. The snuffs originates at a point and grows wider while it sweeps up more and more snow in its descent. On the other hand, the Slab avalanches originate in snow with sufficient internal cohesion to enable snow layer(s) to move as single entity.

What are the causes and effects of snow avalanches?

The causes of avalanches include many factors such as topography, vegetation, weather conditions, weight of snow cover, geological factors such as earthquakes etc. The effects of snow avalanches include minor to huge loss to life and property. Small avalanches can block highways and train-tracks blocking movement, while large avalanches can kill hundreds of people and cause loss of manmade structures.

What are the snow avalanche prone areas in India?

In India, Himalayan region is well known for occurrence of snow avalanches particularly the Western Himalayan region (Jammu and Kashmir, Himachal Pradesh and Uttarakhand).

Do landslides function the same way as avalanches?

Basically yes because both landslides and snow avalanche are types of mass wasting. Both are geological hazards and gravity is important factor causing both of them. The key difference between snow avalanche and landslide is that the material in snow avalanche is more homogenous (mostly snow) in comparison to landslides (which is more heterogeneous and comprises soil, rocks of various sizes and earth layers).

What is difference between Snow avalanche, Blizzards and Hailstorms?

Avalanche is a swift movement of snow, ice, mud, or rock or a mixture of them down a mountainside or slope. Blizzard is a very strong, bitterly cold. wind accompanied by masses of powdery snow or ice crystals often with poor visibility. Blizzards generally occur in high altitude and polar areas. Hailstorm refers to a sudden heavy fall of small hard balls of ice.

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