Friday, 17 April 2020

Skier killed by avalanche in Summit County, Colorado.

A skier has died after being caught in an avalanche in Summit County, Colorado, on Wednesday 15 April 2020. The incident happened at about 1.40 pm local time, on Red Peak, to the north of Silverthorne in the Gore Range. Deceased was reportedly one of three skiers, described by local reports as experienced and well equipped, that had ascended Red Peak earlier that day and were making a descent through a narrow gully known as Oh What Big Eyes You Have, when the avalanche struck. Two of the skiers were caught initially, but one was only carried a few meters, while the other was swept about 250 m downslope and subsequently died of his injuries. This is the latest in a series of lethal skiing accidents in Colorado this month, despite pleas from local authorities for people to avoid travelling to the area during the Covid-19 epidemic, in order to free up local emergency services to deal with that crisis.

The approximate location of the 15 April 2020 Red Peak 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.

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