The First Ski Descent of Canada's Deltaform Mountain

Years ago, when Guillaume “Gee” Pierrel was at Moraine Lake, he was a tourist. 

The glittering body of water near Banff, Alberta, is ringed by a series of towering, jagged peaks that, historically, appeared on the back of Canadian twenty-dollar bills. Like many other sightseers who’ve stopped by to soak in an unforgettable alpine view, Pierrel took a picture. He thought the peaks were protected, and you couldn’t climb them.

However, those mountains, part of the Valley of the Ten Peaks, have seen several firsts. And last month, a crew that included Brette Harrington, Christina “Lusti” Lustenberger, and Pierrel—now a leading ski mountaineer—added another. Their target? The 11,234-foot-tall Deltaform Mountain. To be more exact: a snow ramp pockmarked by seracs, or sheer ridges of unskiable ice. Rock spires loomed on either side. No one had skied it before.

“It looks gnarly,” said Pierrel. “It's not super welcoming.”

Collectively, the trio had already spent hours and hours in the mountains. In 2024, Lustenberger and Pierrel first skied together in New Zealand, climbing and skiing several high-consequence lines, like one they called Hunter’s Moon—hardly a mellow way to cement a new ski buddy. Since then, they’ve remained consistent and successful partners, having notched a first of the Great Couloir on the storied Mount Robson.

“[We have] the same motivation, same temperature to a very intricate ski alpinism style of skiing that is technical on the ascent, technical on the descent,” said Lustenberger, of their partnership. “I've learned a lot from him. He pushes me.”

Lustenberger’s shared resume with Harrington, a multi-hyphenate mountain athlete, is similarly impressive. She helped Harrington jump from climbing into ski mountaineering. The two pooled their skills as they attempted more difficult descents. Eventually, they skied an impossible-looking route on Baffin Island. It had another lunar name, hinting at the otherworldly landscapes of ski mountaineering: Polar Moon.

Lustenberger was behind what would become their latest project in the Valley of the Ten Peaks. The route, the North Glacier, was first climbed in 1968. Now, though, as the glacier has shifted and receded, it’s no longer mentioned in current guidebooks. Lustenberger wanted to ski it. Harrington, who’s spent time climbing in the area, was game. Pierrel, for his part, tends to say yes to Lustenberger’s plans, even before he knows the details—a fact he and Lustenberger laughed about.

“She's a leader,” said Pierrel. “But she was not saying yes or no. It was a very, very nice discussion between the three of us, respecting and listening to everyone’s point of view.”

That vision led to Deltaform Mountain. To reach it, the skiers dragged toboggans about ten miles, establishing camp within sight of the North Glacier. They arrived in the afternoon with a few hours of daylight to spare, melting snow and cooking food before going to bed.

They didn’t climb the same route they planned to ski—the seracs, which can shed ice, made that too dangerous. Despite the cold, mountains don’t remain frozen in place. They throw all kinds of obstacles at mountaineers, from rocks to avalanches. So, instead, they ascended a path to the side of the North Glacier. As the group clambered up, they saw a small chunk of ice cleave off into the void.

“It was humbling to see that and be reminded that when you are underneath these things, you can't predict it,” said Lustenberger. “You just have to do what you can to move efficiently.”

While the team used a rope to rappel onto the upper part of the North Glacier and finish the ascent, they were untethered for much of the climb. The reasoning behind that, Harrington explained, was that the climbing didn’t feel hard enough to warrant a rope. At the same time, slipping could prove fatal.

Harrington, whose repertoire ranges from sport climbing to big wall climbing, said the experience was most like free soloing—the rope-free flavor of climbing made famous in the public eye by Alex Honnold. All three skiers are among the best at what they do, from minimizing risk to route-finding, but the mental weight of that exposure can prove tiring.

“I think that was the biggest challenge for me,” Harrington said, noting that she hasn’t skied a big line in around two years—she’s been more focused on rock climbing. “Maintaining consciousness to every single step throughout the entire day was draining a bit.”

The exposure continued during the descent. Clicking into their skis, their run started on a hanging, glaciated snowfield that ended in nothingness. Lustenberger noted, unsurprisingly, that in these situations, focus is very important. You have to be certain of your every movement and how the snow feels, especially as you approach the edge. There’s no room for error. They skittered up to the first serac, built an anchor, and rappelled down. 

A few more rappels brought them to the apron below the line, and they skied back to camp, where they could share a high five, gazing upwards at the North Glacier. Talking to skiers of their caliber is, at times, confounding. They exist in a realm that photos, stories, and conversations can’t quite capture—it’s almost superhuman. 

But even Lustenberger, who can seem impervious to fear, said that as she pushes her lines further, casual outdoor adventures are becoming more appealing. Before we spoke, she and Pierrel had spent the day snowboarding at Kicking Horse Mountain Resort—a sport in which Lustenberger is a total beginner.

“We were both saying how fun it was just to do something that's fun because it's not scary or dangerous or might kill you,” she said. “It's because it's fun and you're doing it with your friends.”