Written By Tyler Pecore for News Media Writing with editing from the Indy staff
Some of the most dangerous backcountry skiing conditions in the country are located in Colorado.
On average, six deaths and 60 injuries per year are reported in Colorado, said Spencer Logan, a weather forecaster for Colorado Information Center.
One out of three people die of trauma from avalanche slides, Logan said.
The largest reason Colorado’s backcountry is so dangerous is the seasonal snowpack, said Tom Whalen, assistant coordinator of Outdoor Pursuits.
Colorado’s specific snowpack is called a shallow snow pack, Whalen said.
Other dangerous factors are represented in what is called the Avalanche Factor Triangle, Logan said.
Snowpack, terrain and weather factors make up the sides of the triangle, while the middle is filled with the human factor, Logan said.
Snowpack is the amount of snow from different storms that accumulates over the winter season, Whalen said.
The snow will stack up from different storm conditions, creating a layered snowpack with different types of snow crystals, he said.
Snowpack stability is based on how each layer is structured, he said.
The base layer, made by the first snow of the season, determines how likely it is that the snowpack will fracture on the mountain and result in an avalanche, he said.
A shallow snowpack has a weak and unstable base layer that fractures easily, Whalen said.
A disparity between the warmer ground temperature and the cooler air temperature in Colorado is a major factor behind the state’s shallow snowpack.
The ground beneath the snow maintains a constant temperature of about 32 degrees Fahrenheit, or freezing point, Whalen said.
When the ground is warmer than the cold air above, the snow forms snow crystals that vary in shape and size, he said.
The new snow crystals are called depth hoar snow, and are faceted and weak, he said.
Colorado has very cold nightly temperatures in the high country that drop below zero. These work with the hot day temperatures to result in the forming of these crystals up and down the state’s mountain ranges, Whalen said.
The crystallization process is called temperature gradient, and reflects these high to low temperature changes every 10 centimeters of snow from the ground, he said.
Depth hoar snow is weak and doesn’t hold together, so it doesn’t allow stable structure, he said.
One might imagine this base layer as a stack of cards slipping over one another, he said.
Each ski season, Colorado’s first base layer of snowpack is made up of this depth hoar snow.
Disturbing the base layer is like destroying a support column from under a building, Whalen said. Once this metaphorical column is gone, the snow will fracture and an avalanche will release from that point, he said.
Avalanches release on slopes that are at a 30 to 40 degree angle, because those angles create a stress point from gravity and the wind, he said.
This angle range is similar to the butte that Fort Lewis College stands on.
When riding this type of slope, the wind is a more serious factor than the gravity, Whalen said.
When the wind blows over the mountain to the other side, it is called a rollover, he said.
The wind will mount itself over the rollover and ride the mountain until the slope on the other side drops off to the 30 to 40 degrees stress point, at which point the wind will stop traveling down the mountain, he said.
This point of air separation is where the snow is most stressed and most likely to fracture, he said. This is because of the pressure the wind creates as it releases from the snow’s surface.
Avalanche fractures will occur if the snow is weak enough that day, Whalen.
One major thing to remember when going out into the Colorado backcountry is to be aware of the conditions.
“Always pack your brain when you go out there,” said Brett R. Davis, coordinator of Outdoor Pursuits.
Be aware of the steepness of the slope, the snowpack and the wind’s wear and tear on it, Davis said.
To avoid avalanches, one should dig snow pits and perform proper snow pit tests to check the danger of the snowpack, he said.
If the snow pit tests show weak and easily fractured snow, move on to the next slope because the danger will never be worth it, he said.
Even with precautions, accidents happen and people get buried, Logan said.
When an avalanche buries a victim, responders have a five-minute window of opportunity to find the person before he or she runs out of oxygen, Logan said.
After that point, the victim will pass out from lack of oxygen to the brain, he said.
After 30 minutes of being buried, the person will have a slim chance of survival, Logan said.