Unstable weather conditions and growing enthusiasm for backcountry sport may be behind the worrying trend

Graphic detail

OVER THE past decade, avalanches have killed an average of 27 people in America every year. It took only until February 17th, halfway through the winter-sports season, to reach that number this year, according to the Colorado Avalanche Information Centre, a state agency. So far 33 skiers, snowboarders and other adventurers have been killed by avalanches, mostly in the mountainous western states. In one particularly deadly week in early February there were more avalanche fatalities than any other week in the last 100 years. On current trends, there could be as many as 51 deaths this season, surpassing the previous record of 36 (see chart).

In a sense, an avalanche is a simple phenomenon—little more than snow sliding down an incline. Yet numerous things can cause the various layers of snow that gather on mountains, collectively called a snowpack, to come tumbling down. Wind strength and direction, which way a slope faces and the level of vegetation all play a role. Avalanches can also be triggered by earthquakes or slightly warmer weather that causes a layer of snow to lose its grip on the layer below. People are also frequently to blame. Although avalanches triggered by backcountry adventurers tend to release less snow than those triggered by other causes, they are often deadlier.

This year many snowpacks have been dangerously unstable. A period of prolonged dry weather weakened the base laid down by the winter’s first snowstorms. Then in late January and early February, heavy blizzards dumped masses of fresh snow on top. What’s more, some suspect that more people have taken to the backcountry this year looking to divert themselves during the pandemic. Although it is too early to know for sure whether this has led to more deaths on the slopes, the number of human-caused avalanches has been higher this year than in the past.

Avalanche fatalities have been creeping up for years. (In the 1950s the annual average was only four). Climate change may be partly to blame: over the past few decades less snow at lower elevations has led to a decrease in the size and run-out distance of avalanches, but an increase in avalanche activity involving wet snow higher up. Still, the main culprit is probably the growing popularity of backcountry skiing, snowboarding and snowmobiling. As people migrate from manicured ski slopes to the wilds, the risk of avalanches naturally increases. Thanks to improvements in equipment, intrepid skiers have been able to stray ever farther off piste. The Colorado Avalanche Information Centre has said that incidents are becoming less probable, but more dangerous. It might be best to stay off the slopes for now.