It’s all about the clues
December 16, 2003
BRECKENRIDGE – Avalanche forecaster Nick Logan says backcountry enthusiasts can go ahead and take risks – but only if they are armed with the right information.
“We’re not trying to scare people out of the backcountry,” he says. “Avalanches are beautiful to watch. They’re real powerful. Some are silent, some are noisy, some are fast and some are just dust clouds.”
They’re also dangerous.
Colorado leads the nation in avalanche deaths, followed by Alaska, Utah, Montana, Washington and Wyoming. Most deaths have been snowmobilers, followed by backcountry skiers, then climbers, people skiing out of bounds, backcountry snowboarders and finally, ski patrollers. This season, two people have died in avalanches in Colorado and another 53 – 10 in the past two weeks – were caught in slides but escaped.
“We’ve been real lucky,” Logan says. “Eight of those people were buried, 10 were injured and 17 were partly buried. A lot of times, people just had a hand out, or people get to them just in time, give them a couple breaths and they made it.”
Six skiers near Berthoud Pass triggered a slide Monday, trapping one up to his waist.
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Three factors – snowpack, weather and terrain – go into making an avalanche.
Humidity is responsible for the initial shape of snowflakes. But early-season snow and temperature fluctuations melt and smooth the pointed snowflake crystals, making them less likely to bond to one another. The weight of additional snow on old snowpack also breaks down the snow crystals, making them into a compact grain.
When the next storm moves through, new snowfall doesn’t affix to the old, rotten snow, Logan says. Snowpack then awaits a trigger – be it wind, a human or sheer stress on the snowpack – to slide.
Clues that an area is prone to avalanches include previous slide paths, flag trees – those with broken, uphill branches – and cracks along the snow surface. Backcountry enthusiasts also should pay attention near rocks, Logan says. While some might be safe refuges, snow in the area can be weak because the sun heats rocks, causing snow to “rot.”
Temperatures, humidity and wind also affect avalanches. Changing temperatures melt and refreeze snowpack, making it less stable.
“If the temperatures increase fast enough, they’ll destroy the bonds between the old and new layers,” Logan says. “Snow’s just like Silly Putty. If the temperatures change slowly, it’ll adjust. But if they change fast, it gets real brittle.”
Wind wicks moisture from the snow, and humidity controls the types of crystals that land on the slopes. And snowfall of an inch an hour for several hours increases the possibility of avalanches.
Wind also pushes snowfall to the leeward side of the mountain, where it builds thick cornices and drifts that are prone to slide.
Avalanches typically slide from a single point and progress outward, or in a slab from a horizontal fracture line. Some merge with other slides in neighboring chutes, and others trigger avalanches nearby. When the snowpack finally gives way, the snowflakes are pulverized into tiny grains that pack tightly as the snow roils down the slope. And if someone is trapped in the slide, the snow can embed them in what feels like setting concrete. A Breckenridge man rescued from an avalanche near Arapahoe Basin late last month said he couldn’t even open his eyes.
“The human factor is huge in avalanches,” Logan says. “You think, it took you hours to get there; you’re going to ski it. People are often unwilling to bend to these factors. You have to think, `Will it avalanche?’ and, `If it does, where will it take me?'”
The results of being trapped in an avalanche aren’t pretty, either, he says.
“You get compressed,” he says. “It squeezes you extremely tight. It’s not fun for you, not fun for your family, not fun for your partners.”
Someone trapped in a slide for less than 15 minutes stands a 90 percent chance of survival. At 30 minutes, however, that drops to 50 percent.
“If you’re killed, hopefully you died from trauma and not by suffocation,” Logan says.