Devastating Avalanche in Uttarakhand

Sub: Geo

Sec: Geomorphology

Why in News

A massive glacier avalanche struck a Border Roads Organisation (BRO) project site in Mana village, Uttarakhand, leaving 22 workers trapped under ice. The rescue operations, led by the Indian Army and Indo-Tibetan Border Police (ITBP), have been hampered by continuous snowfall.

Avalanche:

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.
In India, Himalayan region is well known for occurrence of snow avalanches particularly 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. This layer 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.
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 its 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.

About BRO:

The Border Roads Organisation (BRO) is a statutory body under the ownership of the Ministry of Defence of the Government of India.
BRO develops and maintains road networks in India’s border areas and friendly neighbouring countries.
It is staffed by officers and troops drawn from the Indian Army’s Corps of Engineers, Electrical and Mechanical Engineers, Army Service Corps, Military Police and army personnel on extra regimental employment.
Engineering Service and personnel from the General Reserve Engineer Force (GREF) form the parent cadre of the Border Roads Organisation.

IBEX Brigade:

The IBEX Brigade is a specialized unit of the Indian Army, known for its expertise in high-altitude operations.
Recently, led rescue operations in Mana Village, Chamoli district, Uttarakhand, following a glacier avalanche.