Item: Snow temperature patterns and artificial avalanche release
Title: Snow temperature patterns and artificial avalanche release
Proceedings: Proceedings of the 1992 International Snow Science Workshop, Breckenridge, Colorado, USA
Authors: Nicholas Logan
Abstract: Temperature gradient plays a vital role in snow metamorphism. Acting as a heat source, rock outcrops buried in the snowpack produce stronger local gradients than are found in areas without rocks. Thus, the area of depth hoar growth increases around rock outcrops and creates local regions of stress concentration. This reduces snow strength and creates likely regions for triggering an avalanche. Indeed, when examining a selection of Colorado avalanche accidents, the trigger zone can be linked to kinetic metamorphism around local terrain features. This report presents nine backcountry incidents that support this finding. While this has implications for snow safety management in industry, such as ski areas and transportation, emphasis in this study is placed on human-triggered avalanches resulting in backcountry accidents. Education that promotes safer route finding techniques based on avoiding stress concentration areas can reduce the number of avalanche accidents involving backcountry travelers. To depict how snow properties are influenced by the temperature gradient, a review of snow metamorphism and a summary of snowpit data are provided as supplemental information. Only dry slab avalanches, typical of the realm of a shallow, low-density snow climate, are addressed. It is in this environment that the rate and intensity of kinetic metamorphism can vary significantly across a potential avalanche slope.
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Keywords: temperature gradient, metamorphism, triggering,
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