Depth hoar

"Sugar snow" as a layer in a snowpack

Depth hoar crystals, imaged with light and with scanning electron microscopy

Sugar snow - panoramio

Depth hoar, also called sugar snow or temperature gradient snow (or TG snow), are large snow-crystals occurring at the base of a snowpack that form when uprising water vapor deposits, or desublimates, onto existing snow crystals. Depth hoar crystals are large, sparkly grains with facets that can be cup-shaped and that are up to 10 mm in diameter. Depth hoar crystals bond poorly to each other, increasing the risk for avalanches.

The formation of depth hoar in Arctic or Antarctic firn can cause isotopic changes in the accumulating ice. This can influence analysis of ice cores in scientific research.

References

• Pfeffer, W. T.; Mrugala, R. (2002). "Temperature gradient and initial snow density as controlling factors in the formation and structure of hard depth hoar". Journal of Glaciology. 48 (163): 485–494. doi:10.3189/S0022143000002008.

Further reading

• Depth Hoar, Avalanches, And Wet Slabs: A Case Study Of The Historic March, 2012 Wet Slab Avalanche Cycle At Bridger Bowl, Montanamontana.edu.
• The formation rate of depth hoar J. C. Giddings E. LaChapelle, First published in June 1962.

External links

• The Avalanche Encyclopedia, extensive summary with animation of formation process