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Three weeks ago in the California ski resort of Alpine Meadows near Lake Tahoe, seven people were killed by an avalanche. Four more were spared from death—all of them quite miraculously, and one of them a lot more miraculously than the other three. Despite a booming four-day blizzard, every applicable form of safety measure and avalanche-control practice had been undertaken on that besieged mountainside. Moreover, no avalanche of that magnitude, nothing even close to that size, had ever occurred on that slope before. The odds were hugely stacked against such a disaster. Yet seven people are dead, four alive by miracle.
And therein lies the bleak and bitter truth about avalanches: They are wildly capricious killers. They stand among nature's most volatile, most deadly creations. They are also among her most frequently occurring phenomena—yet they remain, as far as human intelligence has been able to divine, as erratic and as enigmatic as they are awesome. For the better part of a century, glaciologists, foresters, ski-area designers, snow scientists and just plain citizens of the world's mountains have been applying every instrument and insight that modern science, computer technology and common sense can bring to the problem of understanding and controlling avalanches. They have made enormous progress, and yet Knox Williams of the U.S. Forest Service's avalanche research project in Fort Collins, Colo. speaks for them all when he says, "The more you know about avalanches, the more you come to understand that you will never know enough."
There are certainly enough of them to get to know. In the Alps there are some 11,000 avalanches in an average year. In the far vaster mountain ranges of the Western U.S., there are about 10,000 annually (many of them man-made through control techniques) that people actually observe, and God only knows how many tens of thousands more that thunder, hiss or glide noiselessly down slopes far from human habitat.
Avalanches are nearly infinitely varied—differing in shape, size, density, sound, momentum, esthetics, destructiveness, etc., etc., etc. Some are small, pretty sloughs of powder that flow downhill in lovely teardrop tongues, liquid as syrup yet sending up plumes of snow smoke as they go. Some are immense slabs that cover acres of ground, thick and dense and wind-pounded to the consistency of a million-ton tombstone. Avalanches may start with a whoomp that sounds like a blast of dynamite, then spread in crazy fractures across the mountainside and then break into blocks the size of house trailers, which are, in turn, pulverized by the turbulence of the slide into flying snow-smithereens tinier than snowflakes, which, in turn, then set as solid as concrete when they finally grind to a stop.
The natural forces generated within an avalanche are among the most stupendous on earth: wildly fluctuating densities of mass, strange hydraulic imbalances, weird increases in speed, massive changes in air pressure, heat wrought of friction within the mass, enormously high levels of specific gravity. All this is caused by the simple power of a relatively large mass moving at relatively high speed. And it can be terrifying stuff. For example, a slab avalanche can routinely skim along at an average rate of 50 or 60 mph, which is faster than any skiers except high-level experts going full-out can attain. The thought of trying to outrun something with the mass of, say, half a dozen ocean liners while it chases you at a speed exceeding the freeway speed limit is something calculated to turn any skier's knees to water. Yet it could be worse.
If the incline of the slope is steep enough and long enough, then a big, heavy slab avalanche can accelerate to speeds of considerably more than 100 mph. And at that point, the laws of hydraulics and aerodynamics being what they are, the force of the avalanche wall slamming ever faster against normal air resistance creates an air blast-wave in front of it. This ultimately can produce an imbalance in pressure that will actually cause the mass to accelerate faster than gravity is moving it because, according to current theory, it is being sucked powerfully ahead into a semi-vacuum.
This imbalance in pressure occurs in less dense powder avalanches to such an extent that a mass of snow has actually been measured moving at the speed of 240 mph! Incredibly, that is faster than the rate at which a body free-falls through space. (Due to air resistance, this rate of fall is rarely more than 180 mph.) An avalanche moving at more than 200 mph generates all sorts of bizarre actions—outside as well as inside the mass. Dr. Herbert Aulitzky of the Vienna Agricultural University, one of Austria's leading avalanche experts, says, "A powder avalanche hurtling along at 240 mph really in many ways resembles a hurricane—except for the fact that its density, caused by the mass of snow, is a great deal more destructive."
The air pressure generated in front of such a blindingly fast-moving mass of snow has been known to reach, according to Dr. Aulitzky, as much as 220 tons per square meter, compared to average air pressure of 11 tons per square meter. That means getting hit by a square meter of this avalanche blast-wave would be roughly equivalent to being run over by two locomotives. Obviously, the destruction in the path of such a force can be far worse than even that caused by the avalanche itself. Huge trees are leveled, buildings actually explode, and bodies have been found, crushed and broken, hanging from trees well ahead of the point where the sliding mass actually stopped.
At these high speeds, the workings of friction inside of the onrushing snow mass can build up enough heat to actually melt the snow. Then when the mass comes to a stop, the whole thing turns instantly dense, becomes inert and freezes solid, encasing any victim who is caught within in a body-fitting casket made of ice.
All of these things can happen in routine, everyday large avalanches. The destructive power of a truly monstrous avalanche is almost beyond imagination. No flatland tornado, no hurricane at sea ever produced more punishment to human life or property than a major avalanche. Indeed, some experts are convinced that nothing in nature—with the exceptions of major volcanoes, earthquakes and gargantuan flash floods and tidal waves with their immensely dense speeding walls of water—can surpass the destructive potential of a monstrous avalanche. One case to prove that awful point occurred on Jan. 10, 1962 when a section of the ice cap broke from just below the 22,205-foot peak of Peru's North Huascarán, the seventh-highest mountain in South America. The falling ice tore away vast acres of glacial snow and ice around the summit, plunged 3,000 feet down a sheer face and hit a shallow bowl with an impact that was heard for miles. The concussion from that set up a swirling cloud of powdered snow and also produced a huge secondary avalanche behind the first, and this constantly growing mass shot down the slopes at 65 mph, picking up uncountable tons of rocks and snow and ice as it raced down valleys, rolled over plateaus and, here and there, actually climbed uphill slopes.