For many centuries and in many cultures, people associated the sudden, terrifying onslaught of rolling, isolated snow- storms with angry gods, evil demons or monsters, and even the practice of the dark arts. A trial in Switzerland in 1652 concluded authoritatively that "witches are the causes of avalanches,"6 and there are other documented instances of people being put to death on suspicion of having conjured up an avalanche.

The eerie randomness of avalanches' destruction helped reinforce the notion that mysterious forces were behind these occurrences. For example, one powerful avalanche in 1806 tore up a large section of forest in the Alps, but the hurtling mass of snow and tree trunks sailed over a nearby village without causing any harm. There was, however, a spectacular reminder of the near miss: A single tree trunk embedded itself and stood straight up in the roof of...