The avalanche that killed a Bozeman snowmobiler riding in the Gallatin Mountains on New Year’s Day – the first Montana avalanche death in more than a year – was somewhat of an anomaly, according to an expert.
“Most avalanches happen when people are on the slope,” said Doug Chabot, of the Gallatin National Forest Avalanche Center. That can happen when a snowmobiler is riding across a hill or uphill, or when a skier or snowboarder is carving turns downhill.
But the avalanche that killed 46-year-old Burton Kenneth Gibson was what’s called a remote trigger avalanche – when a slide is caused by collapsing of the snowpack from what may look like a relatively flat or safe area.
“When there’s a weak layer in the snowpack, in order to get an avalanche we need that weak layer to collapse,” Chabot said.
He said the unstable snowpack found in the mountains of southwest and south-central Montana right now is like a book resting atop potato chips.
“When it’s really unstable and we collapse a weak layer, it’s almost like dominoes falling,” he added. “It propagates out and can go up the hill. In a split second, it’s moving close to the speed of sound. When it gets to a steep slope, it breaks.”
Burton and his companions were riding in a large bowl at the head of Porcupine Creek called Onion Basin, southeast of Big Sky. When the avalanche broke on the mountain above, it collapsed 400 feet wide and 2 to 3 feet deep and then ran 1,100 feet downhill – a drop of 500 vertical feet, according to the avalanche center’s accident report released over the weekend.
Burton was found buried on his side about 3 to 4 feet deep near the bottom of the avalanche, called the runout zone. His fellow rider, who was identified only as a 19-year-old man, was pushed into trees on the slope behind and above Gibson and was buried with only one hand free.
“It was pure luck” that he wasn’t completely buried, too, Chabot said. Trees offer no protection in avalanches and more often injure victims swept through them.
“Going into trees is always bad,” Chabot said.
With only one hand free, the teen was able to dig down to his head and then free his other hand. He then dug out around his backpack to retrieve a shovel and dig himself out the rest of the way.
The survivor estimated it took him a half-hour to get free from the snow, which in avalanches sets up so solid it’s often compared to digging in concrete.
“That kid was dialed in,” Chabot said.
To dig himself out, try to call 911 (there was no service) and then do an avalanche beacon search for his partner and dig him out required a clarity of mind that many avalanche victims don’t possess, he said. Once he reached Gibson, the teen attempted to give Gibson CPR before a third riding partner arrived and assisted.
“A lot of people freak out and leave” to get help, Chabot said.
Although Gibson was found ahead of his companion, he had been riding about 100 feet behind and below the leader before the slide.
The surviving partner and investigators figure that Burton realized the avalanche was coming and tried to speed away downhill and outrace the avalanche. Avalanches can reach speeds of 80 mph.
“That makes sense,” Chabot said of Gibson’s response. “That can work. It’s not an unreasonable reaction.”
It also explains how Gibson ended up in front of his fellow snowmobiler.
The report also noted that Gibson was wearing an air bag avalanche rescue device. The safety gear is worn like a backpack. When a cord is pulled, large air bags quickly inflate. The bags add mass and flotation, keeping the avalanche victim closer to the top of the slide.
But Gibson never pulled the ripcord.
“What some people don’t realize is you have to pull them quickly,” Chabot said. “They have about a 30 percent non-deployment rate.”
Chabot said he asked the other rider if he would have had time to pull a cord, and he said no, that the avalanche struck too quickly.
There was a third man, also 19, riding with the group, but the accident report reveals he had gotten stuck before the two riders reached Onion Basin where the accident occurred. That delayed his arrival at the avalanche until after his friend had dug himself out and started CPR on Gibson.
With darkness falling and unable to revive their friend, the two rode out by the Portal Creek Road to their vehicle on the one snowmobile that wasn’t buried and damaged. Gallatin County Search and Rescue used a helicopter to retrieve Gibson’s body the following day.
Before last week’s accident, Montana’s most recent avalanche fatality was on Feb. 25, 2012, in the Marias Pass area. That year saw six avalanche fatalities in Montana, only one of which involved a skier. Wyoming had three avalanche fatalities in 2012, and three in 2013, only one of whom was a snowmobiler. In 2013, Montana managed to avoid any avalanche fatalities.
Nationally, 24 people were killed in avalanches last year, and 17 of them were skiers and snowboarders. In one incident in Colorado, five snowboarders were killed.
On Monday, avalanche danger was rated “considerable” in southwestern Montana by the avalanche center, which issues daily reports. When the fatality occurred last week, the danger was rated high in the area where the snowmobilers were riding.
“They knew things were bad and why, that’s the best we can hope for,” Chabot said.
The snowpack is weak because subzero cold in early December created faceted snow that, when buried under later snows, can act almost like ball bearings for the heavy new layers of snow to slide on.
“I’m optimistic things will get a little better,” Chabot said. “Time and more snow helps. It starts to crush those weak layers.”
Until the snowpack settles, though, more snow may increase avalanche danger, he added.