Avalanche refers to a mass of snow, ice, and rocks sliding hastily down a steep slope.

Avalanches occur in many formats and sizes – transferring unfastened snow to the displacement of vast slabs of snow. A slab avalanche is far more damaging than unfastened snow displacement, as it can destroy forests and small villages in its course. Proper prediction is required and protective measures must be taken.

Avalanche Classification

Avalanches are classified into two types – slab avalanches, which are built of tightly packed snow and are caused by the collapse of an underlying weaker snow layer, and loose snow avalanches, which are composed of loose snow. Avalanches often speed up quickly after being triggered and develop in mass and volume as they gather additional snow. If an avalanche travels quickly enough, part of the snow may combine with the air, resulting in a powder snow avalanche.

Avalanches may occur in any mountain range with a persistent snowfall. They are most common in the winter and spring, although they may occur at any time of the year. Avalanches are one of the most dangerous natural calamities that damage life and property in mountainous places; hence, tremendous efforts are made to manage them.

Avalanches are classified based on their magnitude, destructive capacity, mode of start, composition, and dynamics.

Features of Avalanches

• Three principal components of avalanches include the beginning zone, the avalanche track, and the runout zone. Avalanches get released from the beginning zone, usually the riskiest part of the slope, and are typically at the top of the mountain.
• Once the avalanche begins to slide, it passes down the avalanche track, and due to the gravitational route, it goes downhill. After avalanches, massive clearings offer clues to an avalanche’s trajectory.
• An avalanche is then stopped at the lowest point of a slope, inside the runout zone, where snow and particles build up.

Factors Responsible for Avalanches

• Heavy Snowfall: It deposits snow in risky regions and places stress at the susceptible layer of snow, inflicting an avalanche.
• Human Activity: Winter sports activities that require steep slopes input stress at the layer of snow, causing an avalanche.
• Wind Direction: The direction of the wind determines snow accumulation at the mountain slopes.
• Steep Slopes: An avalanche is likely to occur because of the impact of gravity.
• Warm Temperatures: The snowpack melts, and the snow may be fluid.
• Layers of Snow: There are situations wherein snow is already on the mountains and has become ice. Then, sparkling snow that falls on a pinnacle can, without difficulty, slide down.
• Earthquake: It generates seismic waves that cause the ground to vibrate, and matched with the gravitational pull, it’s one of the fastest approaches to triggering an avalanche. 

These are the factors responsible for an avalanche. We need proper planning for the prediction and preventive measures of avalanches.

Glacial Lake Outburst Flood (GLOF)            

GLOFs may have disastrous effects like flooding because of the launch of massive volumes of water in a short period.

For example, in 2021, parts of Uttarakhand witnessed tremendous flooding after a bit of the Nanda Devi Glacier broke off at Joshimath in the Chamoli district of Uttarakhand. This resulted from an improper avalanche prevention structure.

NDMA pointers for GLOF

Some prediction and preventive measures used by NDMA are as follows:

• Identifying and mapping the probably risky lakes via area observations, geomorphological and geotechnical characteristics, satellite TV for PC imagery, etc.
• Using Synthetic Aperture Radar (SAR) imagery to come across adjustments in water bodies, new lake formations, etc.
• Structural measures like pumping or siphoning out water, making tunnels via moraine barriers, decreasing the range of lake formations, etc.
• Regulating land-use making plans and prohibiting the development and infrastructure improvement in excessive threat zones
• Setting up an early warning system, having emergency response teams, etc.

Conclusion

An avalanche (also known as a snow slide) is a fast-moving flow of snow on a slope, such as a hill or a mountain. Avalanches may occur spontaneously due to variables such as excessive precipitation or a decreasing snowpack or as a result of external sources such as people, animals, and earthquakes. Large avalanches, which are mostly made up of moving snow and air, have the power to catch and transport ice, rocks, and trees.