Eleven days after the tragic avalanche that killed a young Durango woman while backcountry skiing with a friend on Kendall Mountain just above Silverton, the Colorado Avalanche Information Center released its final report of the accident.
Olivia Buchanan, 23, was an avid skier and student of snow science at the University of Montana, and Jan. 6, she and friend Ryan Moomey were just out for a good day in the mountains.
The two were experienced back-country travelers and were adjusting their outing, making intelligent decisions based on conditions and terrain they encountered.
"She took every protocol you're supposed to," Moomey told The Durango Herald after the accident. "I was very confident being up there with her."
But the physics of avalanches often are elusive. The slab avalanche - the dangerous kind - where a cohesive layer of snow slides over an incohesive layer, let go at 11,300 feet on a northwest aspect of the mountain, high in a divided gully commonly know as the Rabbit Ears. The conditions leading up to the event can be traced to earlier this winter.
December saw two weeks of dry, mild weather, causing faceting - a formation at the surface and in the depths of weakly bonding snow crystals. In addition, several snowstorms during the last two weeks of December dumped close to 41 inches of snow in the mountains near the site of the avalanche.
According to the report, the suspect layer was found on all but the southern aspects of Kendall Mountain. Buried by later storms - likely one Dec. 13 - and wind-blown snow, this persisting layer about 2 feet below the surface between two harder layers of snow would become the cause of Buchanan's fatal avalanche.
Mountains are mazes of puzzles to be solved, and most of those, at best, are not. Constantly evaluating the terrain and relative danger is challenging for even the most seasoned experts, and the CAIC conducts observations daily across the state to inform the public about inherent dangers that are present in avalanche country.
The slide ran about 700 feet, was 160 feet wide and 2 to 4 feet deep at its crown - the fracture point of where it released. Having avoided obvious signs of instability, Buchanan and Moomey moved wisely, but the danger fluctuated below.
CAIC forecaster Ethan Davis said there are numerous factors to consider.
"The nature and the shape of the mountains and the way weather interacts with them, whether it piles snow deeper on one aspect rather than another, these things can have huge impacts on the snowpack," he said. "The sun, being this far south can have huge effects on the snowpack."
Davis also said an avalanche doesn't need to be big to bury its victim and create fatal consequences.
"Anytime you're accelerated down a slope with fixed obstacles in the way, you're at a pretty large risk of suffering trauma," he said.
According to the CAIC, 30 percent of injuries suffered from trees result in death. Even without trees, it's a matter of terrain.
"The same amount of snow could come down in two avalanches - one could bury you if it piles up at the bottom, and in the other, you could end up on top if it fans out and the end."
He said the CAIC bears that in mind forming their advisories, and backcountry travelers should take heed.
Buchanan and Moomey assessed the terrain they encountered and opted for what they believed was safe passage. But mountains and snow present everlasting conundrums. The slide that day released on a slope of about 40 degrees, below a perceived danger, and led directly into a glade of trees.
While the CAIC concluded that the slide, although small relative to its potential, was large enough to bury a person, Buchanan was found on top of the snow. Despite tremendous efforts in her rescue by Moomey, followed by a rescue team that evacuated her to Mercy Medical Regional Center in Durango, Keri Metzler, the San Juan County coroner, said Buchanan died from multiple injuries, including trauma to her brain, liver and lungs.
In the comments portion of the report, the CAIC stated the two skiers reduced the risks they encountered but also underestimated the extent of those risks and the consequences they held.
"We talk about higher consequence terrain - terrain that's in the trees or can pull you off cliffs," Davis said. "It's hard. You just need to be careful about what kind of avalanches to worry about and where they will be found."
bmathis@durangoherald.com
On the Net
The full report can be viewed at www.CAIC.com.
