Physics of Avalanches Essay

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Avalanches kill back country recreationalists every year, including skiers, snowboarders, snowshoers, and snowmachiners. All back country users should have knowledge of the basic physics of avalanches to help them evaluate local and regional potential for slides. The foundation of this knowledge comes from understanding how the surrounding environmental conditions in previous weeks, previous days, and the day in question all contribute to snow stability or instability, and how specific factors affect snow on a micro-scale, which determines how snow slopes will behave on a macro-scale. There are two major types of avalanches (excluding debris avalanches from broken cornices and ice formations). These are point releases, or loose snow …show more content…
The avalanche increases in horizontal width because snow particles are dislodged laterally, as well. While a surface snow layer that never becomes cohesive is obviously vulnerable to this process, these avalanches often occur when external forces, such as sun and rain, weaken bonding in this layer until cohesion is little enough that some snow breaks free (Graydon and Hanson 1997). The angle of the snow slope ultimately determines at what point cohesionless snow will be able to break free, and varies for the type of snow on that slope. This critical angle at which the snow will begin to slide is called the angle of repose (Daffern 1983). The following diagram shows general breakpoints for this angle of repose. The technical descriptions of the snow types is not important for this immediate discussion, and can be read about in more detail in Daffern's publication (1983). The important point is that extremely cohesionless snow, such as slush, will begin to slide even on the most gradual of slopes, and greater angles are required for progressively more cohesive forms of snow to break free, with well sintered grains being the most cohesive.

While many point release slides remain small and relatively harmless, others can be extremely dangerous if they are just forceful

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