Snow Formation and Avalanches

Articles In This Section:

· Snow Formation and Avalanches

· Snow Texture - part 1

· Snow Texture - part 2

· Snow Texture - part 3

· Stratification of Snow Deposits

· Effect of Slope and Ground Surface

· Avalanche Types - part 1

· Avalanche Types - part 2

· Avalanche Types - part 3

· Detection of Snow Condition

· Summary of Avalanche Causes

· Precautions in Avalanche Territory - part 1

· Precautions in Avalanche Territory - part 2

· Conduct During an Avalanche

· Avalanche Rescue Work

Considering the excellent sliding surface that snow affords, the skier might well wonder, "Why doesn't this snow avalanche?" instead of "Will it avalanche?" Any rugged snow terrain demonstrates that the avalanche is the rule, not the exception. Almost as soon as snow falls, it slides from the steeper cliffs and rock faces. What kind of ground or rock surface, then, will hold it? Once it is held by the ground, what will hold each succeeding snowfall to the snow layer it falls upon? Indeed, what holds one snow crystal to another? These are basic questions, and there are three more: What precautions should be taken in avalanche territory? What should one do if caught in an avalanche? And what can one do for others who are trapped?

Much of this chapter, which endeavors to answer these questions, will seem unduly technical and dryly scientific. Yet the tragic toll of human life taken every year by snow avalanches makes it necessary that every man who ventures onto steep snow slopes be capable of telling when danger exists. He must be able to say with assurance that "this slope is safe," "this slope is unsafe," or "this slope will be safe if we cross it one hour after the sun has left it."

There is no short cut, no easy rule of thumb to determine whether a snow slope is in danger of avalanching. Experience alone is not enough. There may be no chance for a second experience. Required is an accurate knowledge of the internal structure of snow, why it is sometimes packed as hard as concrete, at other times is as fluffy as down, as gritty as sand, as sticky as pie dough, or as slushy as mud. The crystalline structure and texture of snow is in a continual process of change from the time the snow flake is first formed until it either melts or compacts to solid ice. Thorough knowledge of the causes and results of this change underlies an understanding of the causes—and results—of an avalanche.