Why in News?

• A day after two workers were killed in an avalanche near the Zojila tunnel in Sonamarg, Jammu and Kashmir, the area was struck by twin avalanches.
• The State Disaster Management Authority (SDMA) issued a warning regarding avalanches above 2,000 meters over Anantnag, Bandipora, Baramula, Doda, Poonch, etc., in the next 24 hours.

What’s in today’s article?

• What is an Avalanche?
• What are the Main Types of Snow Avalanches?
• What are the Factors that Destabilise the Snowpack?
• What are the Avalanches Prone Areas in India?
• What are the Measures to Control Avalanches?

What is an Avalanche?

• When a mass of snow, rock, ice, soil, and other material slides rapidly down a mountainside it leads to an Avalanche.
• Avalanches of rocks or soil are often called landslides, while snow slides are the most common kind of avalanche.
• A snow avalanche begins when an unstable mass of snow breaks away from a slope and picks up speed and more snow as it moves downhill, producing a river of snow and a cloud of icy particles that rises high into the air.
• A large, fully developed avalanche can weigh as much as a million tons and can travel faster than 320 kms per hour and may lead to loss of life or property.
• 

 What are the Main Types of Snow Avalanches?

• Sluff Avalanches is a small slide of dry, powdery snow that occurs when the weak layer of a snowpack is on the top.
• Slab Avalanches occur when the weak layer lies lower down in a snowpack and when it breaks off it pulls all the layers on top of it down the slope. 

What are the Factors that Destabilise the Snowpack?

• Snow avalanches are most likely to occur after a fresh snowfall adds a new layer to a snowpack.
• Avalanches can be triggered by natural forces, such as the pull of gravity on a steep slope, earthquakes, warming temperatures (weakening the bonds between the layers), wind, terrain, vegetation and general snowpack conditions.
• They can also be caused by human activity, such as the load of a skier, construction/development activities or by use of explosives (to set off hazardous slopes) as part of avalanche control.

What are the Avalanches Prone Areas in India?

• 
• The Himalayas are well known for the occurrence of snow Avalanches particularly Western Himalayas - the snowy regions of Jammu and Kashmir, Himachal Pradesh and Western Uttar Pradesh.
• There are three types of snow avalanche zones –
  • Red Zone: The most dangerous zone that have an impact pressure of more than 3 tonnes per square metre.
  • Blue Zone: Where the avalanche force is less than 3 tonnes per square metre and where living and other activities may be permitted.
  • Yellow Zone: Where snow avalanche occurs only occasionally.

What are the Measures to Control Avalanches?

• Currently, scientists are not able to predict with certainty when and where avalanches will happen.
• However, they can estimate hazard levels and designate vulnerable zones by checking on the snowpack, temperature and wind conditions.
• By building large, sturdy structures to anchor snowpacks and ban unsustainable developmental and tourism activities in Avalanche hazardous zones.