Environment / Natural Disasters

SNOW STRIKE An avalanche rumbles toward the Swiss ski resort of Evolene on February 22, 1999. A catastrophic slide the day before killed nine people.

The eastern face of the mountain is avalanche terrain. There are no trees to anchor the snow. A screaming wind picks up even more snow from the mountain's far side and deposits it onto a bulging cornice that threatens to crack under its growing weight. The slope here is steep, 40 degrees, and the snowpack must cling like a prostrate man on an A-frame roof. Inevitably it loses its grip. To ski this slope after a heavy snowstorm, you would have to be either exceptionally unwise or an avalanche researcher. Four of the latter—Bob Brown, Ed Adams, Jim Dent and Karl Birkeland, of Montana State University—are making plans to do just that. Their destination is a plywood shack in the protective embrace of a small rock outcropping—directly in the path of an avalanche. The structure is nine by six feet, enough room, barely, for two scientists (the rest retreat to the edge of the slide path), an array of instrumentation, a gas-powered generator, and one rather nervous journalist. 

When all is ready, one of the men will ski to the top of the ridge, hoist four pounds of explosives on a pulley out over the crown of the slope, and light the fuse, sending vast amounts of snow down on his colleagues’ heads. If you want to understand the dynamics of avalanches, these men reason, what better place than smack dab in the middle of one?

In the weeks leading up to this event, I have been in the Swiss Alps, because the best way to learn about avalanches is to pay a visit to the very impressive, very modern Swiss Federal Institute for Snow and Avalanche Research (SLF), located in a small ski resort town called Davos. Switzerland spends $2.5 million a year on avalanche research. The architect who designed the raised-marble snow crystal motif on the lobby floor probably got paid more than Bob Brown’s entire budget for 1999. But the Swiss have a compelling reason to spend this kind of money on understanding avalanches: More than 50 percent of them live in avalanche terrain. In the 1998-1999 season, hundreds of major avalanches hit the Swiss Alps, causing more than $100 million in damages and killing 36 people. It was the most destructive season in more than 45 years.  

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SETTING OFF A SLIDE A sign warns skiers away from an avalanche area studied by students and faculty at Montana State University. TK and TK create a path that will direct an avalanche toward the team’s test equipment.

Like Bob Brown and his Montana team, the Swiss also have a mountain avalanche hut. At the moment, it’s out of commission. Last week an avalanche of unanticipated ferocity let loose and destroyed millions of dollars’ worth of test equipment. Just hours before, two men had been in the avalanche’s path installing radar equipment that clocks the speed of tumbling snow. Had fate been running on a slightly different timetable, they would be dead. Immediately after the avalanche, a group of researchers who had watched the destruction debated whether they should venture out and salvage what remained of the equipment. “We thought: Okay, it’ll be very rare that two avalanches hit within five minutes,” recalls physicist Dieter Issler, SLF’s reigning expert on avalanche dynamics. While they deliberated, a second avalanche let go. Avalanche research is a lot like lion taming. Most of the time, it’s safe, but when it’s not, it’s very, very not.

Engineer Bob Brown (top) asembles PVC pipes that contain temperature sensors. Ed Adams (bottom) selects two 2-pound TNT charges to set off an avalanch for study.

Why do researchers risk their lives like this? In part, because few other jobs require one to ski through some of the planet’s most reliably gorgeous scenery. And although there is an inescapable sense that the danger itself is appealing, they do it to save lives. The more that is known about the dynamics of avalanches, the easier it becomes to accurately predict where, and how far, they’ll tumble down any given slope into any given valley. Flow models are employed to make zoned maps that Swiss planners use to keep people from building homes in the runout path of potentially catastrophic avalanches. If researchers know the steepness of the mountain slope, along with various friction parameters, they can calculate how far an avalanche is likely to flow given any number of different slab depth scenarios—a slab being the layers of snowpack that break off and slide down the mountain. One former director of the SLF lives in what is now a blue zone—the second-highest risk zone. In 1968, an avalanche of humbling dimensions stopped, literally, at his door. “Actually, it came in under his door,” Issler says. “Then it stopped.”

Issler stands beside a 10-foot-long Lucite tube containing water and dandruff-sized polystyrene particles. It’s essentially a big, long, banana-shaped snow dome. When Issler presses a button, a sliding door will retreat, sending the particles plunging down the slope, roiling and billowing into a tabletop-scale avalanche.

Issler presses the button, then peers up into the top of the tube. “Hmm,” he mutters. He thumps the Lucite with the heel of his hand. “The person who was in charge of cleaning it has retired,” he says. Finally, his captive avalanche plunges to life. “See, there’s the powder cloud.” A major avalanche—one that runs for 1,000 feet or more—will develop a towering cloud of agitated, airborne snow crystals that rides along above the tumbling snow.

No puff of air in your face, this cloud. This one kills. It snaps conifers like matchsticks and turns vacation chalets into kindling. While the snow portion or “dense flow” of an avalanche will typically stop when it hits an uphill grade, a powder cloud often rushes on, ushering mayhem up and over the top of the hill. The largest powder cloud Issler ever studied was a quarter of a mile high; its 100,000-ton mass traveled three miles before halting.