Snow Avalanche in Uttarakhand

Subject : Environment

Context: Climate change may have had a role in causing the avalanche on the DANDA-2 Peak in Uttarakhand.

Concept :

Avalanche, a mass of material moving rapidly down a slope.
An avalanche is typically triggered when material on a slope breaks loose from its surroundings; this material then quickly collects and carries additional material down the slope.
Snow Avalanche is a rapid, down slope movement of large detached mass of snow, ice and associated debris such as rock fragments, soil and vegetation.
Small avalanches, or sluffs, occur in large numbers whereas large avalanches that may encompass slopes a kilometre or more in length with millions of tons of snow, occur infrequently bust cause lot of damage.
Common types of ice avalanches are Slab avalanches, loose snow avalanches and powder snow avalanches.

Avalanche prone areas

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

Slab avalanches

A slab avalanche occurs when the weak layer lies lower down in a snowpack. Thislayer is covered with other layers of compressed snow.
When the avalanche is triggered, the weak layer breaks off, pulling all the layers on top of it down the slope. These layers tumble and fall in a giant block, or slab.
Once a slab avalanche starts, the slab shatters into many separate blocks. These snow blocks break up into ever-smaller pieces. Some of the pieces rise into the air as a moving cloud of icy particles. The cloud races downhill at very high speeds.
The thickness and speed of slab avalanches make them a threat to skiers, snowboarders, mountaineers, and hikers.
Slab avalanches are, by far, the most dangerous types of avalanches for people.
A slab will move very quickly downhill, up to 130 km/h, starting off as a cohesive unit and shattering into smaller pieces as it descends.

Loose snow avalanches

Loose snow avalanches happen when poorly bonded surface snow slides downhill under it’s own weight.
They are common on steep slopes and are seen after a fresh snowfall.
Since the snow does not have time to settle down fully or has been made loose by sunlight, the snowpack is not very solid.
Such avalanches have a single point of origin, from where they widen as they travel down the slope.
Sometimes called sluffs, these types of avalanches are generally smaller and less dangerous than slab avalanches, but they can still pose a hazard in the wrong terrain.

Powder Snow Avalanches

Powder Snow Avalanches are a mix of the other forms, Loose Snow and Slab.
The bottom half of this avalanche consists of a slab or a dense concentration of snow, ice and air.
Above this is a cloud of powdered snow, which can snowball into a larger avalanche as it progresses down the slope.
The speed attained by this avalanche can cross 190 miles per hour, and they can cross large distances.

Recent Information: Avalanche Monitoring Radar

Indian Army and the Defence Geoinformatics and Research Establishment (DGRE) have jointly installed the Avalanche Monitoring Radar, first of its kind in India, in north Sikkim.
The radar was inaugurated by Tri Shakti Corps commander.

About the radar

This radar has the capability to detect avalanches within three seconds of their triggering and will assist in saving valuable life of troops and civilians as also vehicles in super high altitude areas.
It can scan the targeted slope for avalanche release and track its path and its size in case it is triggered.
It can see through snow, fog as well as in the night, making it an all weather solution and covers an area of two sq/km
The radar is also linked to an alarm system enabling automatic control and warning measures in case an avalanche is triggered.
The radar uses a series of short microwave pulses which are scattered at the target and can detect an avalanche in less than three seconds.