CALGARY, Alberta - First there was a loud crack, and then the avalanche came - a 100-foot-wide wall of rock-hard snow that buried seven backcountry adventurers, including snowboard pioneer Craig Kelly and three other Americans.
John Seibert of Anchorage said Tuesday he has never seen anything like it in more than three decades of climbing mountains, skiing desolate slopes and kayaking wild rivers.
"It was like swimming down the roughest river I've ever been in and trying to keep my head above water," Seibert, 53, said of the avalanche that thundered 300 feet down a remote British Columbia mountainside on Monday.
He was lucky, riding the avalanche until it left him buried except for his head and left arm. The seven who died were buried deeper, as much as 15 feet down, and suffocated. None of the other 13 in the group was injured.
"If you get caught in one of those things, you can't flex a muscle, let alone breathe," said Ian Stratham, of the Revelstoke ambulance service, who arrived at the scene about two hours after the snowslide.
The American dead were identified as Kelly, 36, who lived in Nelson, British Columbia and Mount Vernon, Wash.; Vernon Lunsford, 49, of Littleton, Colo.; Dennis Yates, 50, of Los Angeles; and Kathleen Kessler, 39, of Truckee, Calif.
Three others were from Canada, including Naomi Heffler, 25, of Calgary and Dave Finnery, 30, of New Westminster, British Columbia. The name of a 50-year-old man from Canmore, Alberta, was not released pending notification of relatives overseas.
Seibert, a geophysicist, said the weeklong backcountry ski trip to a mountain chalet accessible only by helicopter was dedicated to safety, starting with a seminar Saturday on using the avalanche beacon each member carried.
He said he detected no signs of trouble as the skiers and snowboarders, divided into two groups, worked their way up a steep slope Monday. Then he heard a loud crack.
"A few seconds later, the moving snow swept me off my skis and I started down the slope," he said. "It's like being in white water until it stops, and then it's like being in concrete."
Survivors helped each other dig out and located the dead, with rescuers arriving by helicopter within 35 minutes. Some survivors stayed on the mountain Tuesday until a helicopter could return for them.
"There was nothing in my mind that was a warning sign we should not be on that slope on that day," Seibert said, calling the tragedy "a fluke of nature."
Sgt. Randy Brown of the Royal Canadian Mounted Police said investigators were looking at what caused the avalanche.
Kelly helped pioneer snowboard riding in the late 1980s and was a four-time world champ and three-time U.S. Open champion. He had become very interested in backcountry snowboarding in recent years, said Tim O'Mara of mountainzone.com, a mountain sports Web site.
All the deaths were caused by lack of air, said Chuck Purse, the British Columbia coroner. He said none of the victims suffered traumatic injuries.
Clair Israelson, director of the Canadian Avalanche Association in Revelstoke, noted that only one other avalanche was recorded Monday in the Selkirk Range, which he called an unusually low number.
To Seibert, the danger is part of the experience.
"I think the risk is well worth the reward," he said. "I've skied 35 years and this is the first time I've been caught in something like this."