Three of the world's top professional climbers are believed to have died following an avalanche near Banff in Alberta, Canada, this week. Austrians David Lama, 28, and Hansjoerg Auer, 35, and American Jess Roskelley, 36, failled to check in with Parks Canada at an appointed time during an attempt to climb the notoriously difficult east face of Howse Peak in Banff National Park, sponsored by clothing company North Face. This prompted a fly-over of the area, which found evidence of a large avalanche on the slope, with scattered equipment among the debris. Attempts to get a rescue team to the site on the ground are being hampered by bad weather in the area.
Austrian climber David Lama, believed to have been killed in an Avalanche on Howse Peak, near Banff, Alberta, this week. Manuel Ferrigato/Red Bull/Associated Press.
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.
Howse Peak rises to 3295 m above sealevel, and 1600 m above the surrounding plain, making it the highest mountain in the Waputik Mountains (a subrange of the Rockies) and the 46th highest peak in Alberta. The mountain has a subarctic climate with temperatures reaching as low as -20°C in winter, when significant snow can accumulate, feeding a glacier on the western flank, as well as the Howse, Mistaya, and Blaeberry rivers. In spring the the area encounters warmer weather, leading to significant melting and frequent avalanches.
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