Searching for clues to the history of snow

Posted: Sunday, March 17, 2002

"Secrets of the Snow: Visual Clues to Avalanche and Ski Conditions" by Edward R. LaChapelle ($12.95, paper, 112 pp., 71 illustrations, glossary, bibliography, index. International Glaciological Society and University of Washington Press).

On one level, Edward LaChapelle's "Secrets of Snow" is a gallery of wonderful black and white photos of visible features of snow surfaces in the mountains. The author, a resident of McCarthy, is a professional snow and ice scientist who compiled these photos over a period of about 20 years. Each photo is a different clue to snow stability or instability.

For example, a photo of a "settlement cone" around the trunk of a deciduous tree is paired with a photo of a cone formed around a conifer, where the snow often connects with snow canopies on lower branches. As the new snow settles around the conifer trunk, "a crack can form between snow cover and canopy. Such signs of settlement are evidence of increasing stability within the new snow," the author writes.

Conditions shown include sluffing, fracture propagation, wind scoops, glide cracks, tree cascades, dimpling, rime, tree bombs, sunballs, cornices, firnspiegels, sparkling surface hoar, erosion and layering.

Photographs were taken in Colorado, Utah, Montana, Washington state, British Columbia, Japan and Alaska.

On another level, this is a valuable, backpack-size book of instructions in choosing places to ski that will not be involved in avalanches. Backcountry skiers who enjoy escaping from groomed routes should read this book to prepare themselves for safe tours of virgin slopes.

LaChapelle writes, "Like the sea, the snow surface is constantly shaped by the wind. Unlike the sea, snow carries the history of this shaping within its internal and external textures. Reading this history is a vital part of reading the snow surface, for wind deposition of snow usually governs both the skiing quality and the mechanical character of unstable slab layers prone to avalanching. For sophisticated forecasting of snow conditions, instrumentation like recording anemometers is essential to follow wind behavior. When such sensors are lacking, as is the usual case for a backcountry ski tour, the wind-influence history has to be observed subjectively, and its past effects deduced from the record etched in the snow surface."

The book is intended by LaChapelle as a companion volume to his "Field Guide to Snow Crystals," published in 1969.

Ann Chandonnet can be reached at

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