Sunday 21 April 2019

Avalanche on Des Poilus Glacier kills one in British Columbia.

A man has died following an avalanche on the Des Poilus Glacier in Yoho National Park, British Columbia, according to Parks Canada. The man was one of three people on the glacier when the avalanche hit at about 1.00 pm on Saturday 20 April 2019, and the only one injured in the incident. He was airlifted to the Foothills Medical Centre in Calgary, but later died of his injuries.

The approximate location of the 20 April 2019 Des Poilus Glacier avalanche. Google Maps.

Avalanches are caused by the mechanical failure of snowpacks; essentially when the weight of the snow above a certain point exceeds the carrying capacity of the snow at that point to support its weight. This can happen for two reasons, because more snow falls upslope, causing the weight to rise, or because snow begins to melt downslope, causing the carrying capacity to fall. Avalanches may also be triggered by other events, such as Earthquakes or rockfalls. Contrary to what is often seen in films and on television, avalanches are not usually triggered by loud noises. Because snow forms layers, with each layer typically occurring due to a different snowfall, and having different physical properties, multiple avalanches can occur at the same spot, with the failure of a weaker layer losing to the loss of the snow above it, but other layers below left in place - to potentially fail later.

 Diagrammatic representation of an avalanche, showing how layering of snow contributes to these events. Expedition Earth.

Des Poilus Glacier is located on Mount Des Poilus, which rises to 3166 m above sealevel, and 466 m above the surrounding plain, in the Waputik Mountains (a subrange of the Rockies). The mountain has a subarctic climate with temperatures reaching as low as -30°C in winter, when significant snow can accumulate, feeding the glacier, as well as the Yoho, Amiskwi, and Kicking Horse rivers. In spring the the area encounters warmer weather, leading to significant melting and frequent avalanches. 

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