Item: Preliminary Results from Controlled Experiments on the Growth of Faceted Crystals Above a Wet Snow Layer
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Title: Preliminary Results from Controlled Experiments on the Growth of Faceted Crystals Above a Wet Snow Layer
Proceedings: 2002 International Snow Science Workshop, Penticton, British Columbia
Authors:
- Bruce Jamieson [ Department of Civil Engineering ] [ Department of Geology and Geophysics, University of Calgary, Calgary, Alberta ]
- Alec van Herwi jnen [ Department of Civil Engineering ]
Date: 2002
Abstract: Faceted crystals have been observed above melt-freeze crusts, and the layers of such crystals form the failure layer for some hard-to-predict dry slab avalanches, Previous work proposed that wet layers could provide the heat to promote faceting in overlying dry snow, resulting in a weak layer of faceted crystals above a crust. A series of seven experiments was conducted in the Rogers Pass Cold Laboratory in February and March 2002. Each experiment involved three snow layers within a laterally insulated box: a lower layer, approximately 15 em thick, of natural dry snow; a middle layer of artificially wetted snow; and an upper layer of dry snow that was sieved onto the wet layer. In different experiments, the wet layer was varied in thickness from 2 to 9 em, and the overlying dry snow (slab) was varied in thickness from 6 to 14 em. The temperature was monitored in the wet layer, in the overlying dry snow layer and in the air, which remained well below O°c. The crystals from the interface and from the overlying dry snow were observed at 20x magnification and photographed through a microscope at least once per day. Faceted crystals were observed above the wet layer in all seven experiments within two days, and in two of the experiments after only two hours, The elapsed time until the wet layer froze was longer in experiments in which more liquid water was added to the wet layer. The maximum temperature gradient near the base of the dry slab was greater in experiments in which the dry slab was thinner. Facets were observed sooner in experiments in which the wet layer was thicker.
Object ID: issw-2002-337-342.pdf
Language of Article: English
Presenter(s): Unknown
Keywords: snow heat flux, snow metamorphism, snow stability, slab avalanche, avalanche formation
Page Number(s): 337-342
Subjects: faceted snow crystals wet snow layer slab avalanche
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