A skier has died in an avalanche near Jackson Hole in Teton County, Wyoming, on Saturday 17 February 2018. The skier, identified as Alexander Marra, 30, of Orrem in Utah, was caught in the avalanche in the Rock Springs Canyon in the Teton Mountains above the town, at about 11.30 am local time and died instantly. Another skier who was with Mr Mara at the time of the incident was unhurt.
The approximate location of the 17 February 2018 Rock Springs Canyon 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.
On this occasion the event has been linked to heavy snowfall the day before the event, with about 20 cm of snow falling in the 24 hours before the event, accompanied by strong southwesterly winds likely to cause drifting, which had prompted local authorities to close several slopes in the area, as well as issuing warnings about skiing in other areas.
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