Snowsafe Blog

Why do mountain rescue services set off controlled avalanches and how? ⛑

Have you ever wondered about Mountain Rescue services and What’s involved? 

They play an important role in looking after and preserving human life, as well as helping make the mountains of the world safer by setting off controlled avalanches.

One of the key parts of this process sees mountain rescue professionals intentionally cause controlled avalanches as part of their job. There are a number of factors behind this, and these are some of the things you need to know about the process. 

Why?

• Risk Management: By intentionally causing smaller avalanches, experts can release unstable snow before it builds up to a dangerous level. This helps mitigate the risk of larger, more destructive avalanches that could pose a threat to lives and property.
• Safety for Communities: In areas like mountain towns, ski resorts, and near railway lines, controlled avalanches can help protect people and infrastructure from the devastating effects of natural avalanches.
• Controlled Environment: Triggering controlled avalanches allows experts to manage the timing and location of the event, minimizing risks to people and property.

Mountain towns, railway lines, and ski resorts where avalanches pose a risk to life will often see and hear explosive charges used to cause smaller avalanches often early in the morning before the lifts open 

How?

Controlled avalanches are typically triggered using explosive charges.

Here are the main methods:   

1. Controlled avalanches, why do mountain rescue services set them off and how? | Snowsafe Blog

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1. Explosive Charges:

   • Hand-thrown: Ski patrol members can manually throw explosive charges onto unstable snowpack.   
      
   • Helicopter drops: Larger explosives can be dropped from helicopters to reach remote or steep areas.   
     1. Controlled avalanches, why do mountain rescue services set them off and how? | Snowsafe
   • Fixed installations: Some areas have fixed explosive charges installed, triggered remotely.  
      

      

2. Gas Explosions:

   • Gazex cannons: These cannons release a mixture of propane and oxygen, which ignites and creates a powerful blast.   
      

      
   • Gas pipes: Gas can be pumped through pipes embedded in the snowpack and ignited to trigger avalanches.   
     1. Controlled avalanches, why do mountain rescue services set them off and how? 

      

3. Avalanche Artillery:

   • Howitzers and recoilless rifles: These weapons can fire explosive shells onto slopes to initiate avalanches.   
      

      

The choice of method depends on factors like the size of the slope, the type of snowpack, and the potential risk to people and property.

There are a few different explosives that can be used to help with this such as:

• Trinitrotoluene (TNT)
• Pentaerythritol tetranitrate (PETN)
• Cyclotrimethylenetrinitramine (RDX)
• Several more

These explosive charges are triggered usually in predetermined areas via Helicopter, Gazex Cannons or Metal pipes fixed to the side of the mountains on high-risk slopes.

Gazex Cannons are large pipes facing downwards which emit hot gases at vulnerable slopes top set off small controlled avalanches. 

There is a Propane and Oxygen Chamber at a distance from the Cannon which is ignited at the base of the Pipe. 

These actions are detonated remotely to keep Mountain Patrollers safe.   

Ski checks are also performed to make sure an area would be safe to ski. Additionally, the avalanches can be controlled by special fences, nets, or artificial walls that can impact what the snowfall is going to do and which direction the snowfall will go in. 

Prevent Further Avalanches

Explosives will loosen small buildups of snow, which will prevent larger buildups from occurring.

The idea here is to control the avalanches by preventing  larger snow clusters from forming.

Mountain rescue researchers will check the environment beforehand, and dig snow pits or using radar technology.

Where?

Many areas of the world need to use these techniques to trigger controlled avalanches. They are commonly known in Utah to keep the train lines clear, as well as countries like Switzerland, and ski resorts across the world.

The idea is to make the slopes a little safer for skiers, and this can sometimes mean manipulating the snow in order to get the best possible outcome.

Can controlled avalanches go wrong?

Yes is your answer, in season 18/19 two ski patrollers were killed in the french resort of Morillon when an explosive detonated before they could move away.

Its important for mountain rescue teams to keep distance from the slides, see video below of a controlled avalanche gone wrong : 

A global standard for professional rescuers   

Recco – Advanced Rescue Technology, More than 900 ski resorts and mountain rescue organizations in 28 countries employ RECCO handheld and SAR helicopter detectors for rescue operations.

“it is very important for one good reason: Time. people that have devices that help us to find them quickly have more chance to survive.”

Laurent Langoisseur 
Ski patrol supervisor at grands montets, Chamonix 

Snowsafe Blogs:

It’s important to stay safe and have the correct training when skiing or snowboarding off-piste please check out further blogs below:

• What is a Recco reflector and why should you always wear one?
• Why do mountain rescue services set off controlled avalanches and how?
• Mountain rescue dogs in avalanche situations
• Mountain Rescue Drones Saving skiers lives from avalanches
• Could there be an app on your phone that is an Avalanche Transceiver?

If you would like to feature a blog about your organisation or experience in the snow please feel free to contact us on info@snowsafe.co.uk or 01273 003925. We are happy to take guest blogs linking back to your website.