Most famous avalanche videos show a white cloud racing down a mountain. Christian Mermoud's clip from Mayens-de-Saxon in the Swiss canton of Valais is the opposite: a thick, heavy tongue of snow creeping out of a wood, pushing over trees with loud cracks as it comes. He uploaded it on 15 January 2016 as "Avalanche Mayens de Saxon Valais Suisse", with a short note in French: rare, slow and very powerful.
Mayens-de-Saxon above the Rhône valley
Saxon is a municipality in the Martigny district of Valais, on the left bank of the Rhône. The village sits at 533 metres, but its territory climbs all the way to the summit of Pierre-à-Voir at 2,476 metres, and about half of it is forest. Mermoud filmed his video at Mayens-de-Saxon, on the slopes of the municipality above the valley floor.
Mid-January 2016 was an active time for avalanches in the Swiss Alps. On 15 January the WSL Institute for Snow and Avalanche Research (SLF) rated the danger at level 3, "considerable", over most of the Swiss Alps and the Jura, warning that "considerable avalanche danger will be encountered over a wide area."
What is a wet-snow avalanche?
The clip was widely shared as a slow-moving wet slide, and it shows the classic look of one. Wet-snow avalanches form only when the snowpack is saturated with water and held at the melting point. They are common in late winter, when strong daytime warming softens the snow, and they can follow rain, which adds weight and lubricates the layers as it seeps down. A rapid rise in temperature well above freezing can set them off at any time of year.
Unlike a powder avalanche, a wet slide stays on the ground and follows the terrain. Friction keeps it slow, typically 10 to 40 km/h. For comparison, powder snow avalanches can top 300 km/h.
Why a slow avalanche can snap trees
Speed is only half of the story. Wet snow is dense and heavy, and a large mass of it moving at 10 to 40 km/h still carries enormous force. Wet avalanches can plough through soft snow and scour boulders, soil and vegetation, often leaving the ground scored behind them. That is what the soundtrack captures: trunks snapping one after another as the mass keeps pushing from behind.
Forests normally do the opposite job. Dense trees help hold snow in place and slow avalanches down. When a heavy wet slide is big enough, though, the trees end up as part of the debris.
Checking avalanche conditions in Switzerland
Check the SLF avalanche bulletin and snow information before any winter outing off the pistes. The European scale runs from 1 (low) to 5 (very high). At level 3, light loads may trigger avalanches on many steep slopes and some medium or large ones can release on their own. On warm afternoons in spring, plan to be off and away from steep sunny slopes early.
For another slow, grinding winter spectacle, watch Dawn LaPointe’s Lake Superior ice-stacking film, and for a gentler side of the mountains, browse Laura Wagemakers’s snowy Alps gallery.
Related reading
- Avalanche Preparation: Training, Terrain, Equipment and Group Decisions
- Run Rabbit Run: The Small Figure in HELIPRO’s Avalanche Film
- James Mort’s Avalanche Rescue in the Swiss Alps: The Survivor’s Account
- Iain Stewart’s Avalanche Documentary: Stories and Snow Science
- The Sicamous Snowmobile Avalanche Rescue: What the Video Records
- Aymar Navarro’s Avalanche Incident in the Spanish Pyrenees
- Sorin Radu’s Snowboarding Avalanche Footage
- Cory Richards on Photography, Survival and Finding a Direction
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