Images of snow bound mountains, deep blue sky, clean and chilled air flash by as one plans of a holiday. Going up the sky lift as if trying to reach for the sky, makes a tourist's heart beat excitedly. The trip becomes a grave tragedy when the snow on the slope decides to move behind the skiers, wrapping them in a white coffin and burying them. One shudders to think how ruthless the snow could be. 

The Wikipedia says that "An avalanche is a slide of large snow (or rock) down a mountainside, caused when a buildup of snow released down a slope, and is one of the major dangers faced in the mountains in winter. An avalanche is an example of a gravity current consisting of granular material"

A large avalanche can dislodge and move snow equivalent to 20 football fields filled with three metres of snow, leaving nothing unturned in its path.

The suddenness and the swiftness of an avalanche have to be experienced to visualize how hazardous it could be. Not only snow, but sometimes the weathered, powdered rock flour produced by the weathering agencies in snowbound terrains moves with the ferocity of an avalanche. While searching for fossil remains of marine organisms up the steep valley slopes of Kurgiakh Chu on Zanskar Mountain in 1975, I had a narrow escape. After the day's work it was a great fun to slide on the 450 slope formed by the weathered material (scree). The accompanying guide, Dorje was almost a midget, barely 3' 8" tall. It was getting late in the evening and we were rushing down to our camp 5000' below in the valley. We were sliding down in a gully of scree material like skiers. Suddenly without any warning Dorje lifted me in his short but powerful arms like a bundle of clothes and dumped me on a small rocky platform on the edge of the channel. I was hurt and slightly bruised. Before I could reprimand him, he pointed towards the silent scree avalanche moving after us which would have engulfed and crushed us. 

Descent that day on the cliff on all the fours, minus ropes was quite a feat and my arms ached for days together. 

However, some 243 people were not so lucky in the avalanches that struck Kashmir in February 2005. For them it was a mass burial in a white coffin. The avalanche was accompanied by high winds. So powerful was the avalanche that 305 people remained stuck inside the Jawahar Tunnel, the entry to Kashmir- the heaven on earth. Continuous snowfall was responsible for the mishap. India Meteorology Department's (IMD) reported snowfall up to two meters in the higher reaches of the Pir Panjal range during 16-20th February, 2005. Crops, plantations and some 10,000 houses in Anantnag, Doda, Pulwama and Poonch suffered extensive damage because of the sudden heavy snowfall.

Swiftness of this avalanche can be imagined from the fact that 300 search and rescue personnel deployed in Banihal Tunnel area had to take shelter inside the tunnel. 

Avalanches have been studied in great detail, all over the world. However, they remain one of the most unpredictable hazards. Apparently calm mass of snow starts sliding down for no reason. Of course reasons are there, but everyone can not be an expert in the science of predicting avalanches. However, knowing a bit about them can be helpful in terms of saving lives.

Anatomy of an avalanche

An avalanche has three main parts. The starting zone, that is generally high up on the mountain slope. It is this point where the snow gathers maximum. It is this point where the snow mass breaks off from the accumulated snow. In case of the avalanche that struck J&K in 2005, the higher reaches of the Pir Panjal range above the tunnel were the starting zone. 

The next part of the avalanche is the channel or the path that the avalanche follows. While the avalanche hurtles down the path it almost 'shaves off' the slope and leaves behind a trail bereft of trees.

The run-out zone is the terminal part where the snow along with the debris picked en route is deposited. After traveling through the restricted 'chute' or the track the avalanche material on approaching the run-out zone just fans out. Compared to earlier two parts this zone is flatter. It is human weakness to seek flat ground for dwellings. Thus a habitation developed on the run-out zone has all the probability of burial under the avalanche. 

Snow avalanches account for a considerable proportion of the earth's present mass movement activity. The higher reaches of the Himalayas in J&K, Himachal Pradesh and Uttaranchal remain under snow cover. In these areas thousands of avalanches occur. Thousands of tons of ice is moved by these avalanches that involve vertical displacements of over 1500 m.

High mountain peaks like the Everest, Lhotse and Nuptse face frequent avalanches. These look spectacular. They are not dreaded by the viewers from safe distances because they do not affect the habitations. It is the avalanches near settlements that are feared maximum. Fir example, villages like Upper Munda and Lower Munda on Banihal-Kazigund section of the road from Jammu to Srinagar and the habitation at Kazigund itself are the places most affected by avalanches. Unfortunately the upper reaches of Kazigund fall in the run out zone of the avalanche. 

Once upon a time Kalpa the old headquarters of Kinnaur district, H.P. was constantly battered by avalanches. It was prudent on part of the government to have shifted the headquarters to Peo, a comparatively safer place.

Avalanches are capable of wiping off the villages. Tunda, a small village in Ladakh was swept off by an avalanche in 1838. 

In their wake the avalanches apart from snow carry lots of boulders, lose rocks, even tree trunks and dump them in the run out zone. If it happens to be the course of a river a blockade takes place. Spiti River valley faced such blockades in 1978. The flash floods that follow such blockades become a nightmare for the habitats downstream. 

Worst part about an avalanche is that it might occur far away from the habitation yet it might take the residents by surprise and leave a trail of tragedy.

We will read more about the causes of avalanches and safeguards against them in the forthcoming issues.