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In July 2020, a young female climber was trapped in a vicious rockfall in the “Corridor of Death” on Mont Blanc, Europe’s highest peak. The Estonian woman was pinned on the steep, open gully, halfway along a narrow path that traverses it. She was balled up tight in a fetal position, her backpack shielding her as stones, dirt and granite chunks, some as large as bricks, rained down. The projectiles ricocheted off her backpack, and one even boomeranged against her helmet, clanking loudly on its metal surface. This short stretch of Mont Blanc’s north face in the French Alps is the Grand Couloir, and it ranks as one of the world’s most perilous for the thousands of climbers, professional and amateur, who seek the mountain’s roughly 16,000-foot summit every year.
“She’s very lucky that the falling rocks weren’t bigger, as they well could have been,” explains Ludovic Ravanel, a French geomorphologist and veteran alpinist. Astonishingly, the woman—whose ordeal was captured in a YouTube video—was largely unharmed, and she was eventually extracted from a nearby perch by the mountain rescue service.
“Most people scaling Mont Blanc aren’t aware of the risk they’re taking,” Ravanel says.
About 100 people die every year in the Mont Blanc range, which includes 11 independent peaks. On the French ascent to Mont Blanc’s summit alone, an average of about ten climbers a year have perished since 2018. That’s more than the death toll on Mount Everest at roughly 29,000 feet, a peak considerably higher and more complex to ascend than those of the Mont Blanc range.
The explanation for this alarming number of fatalities is in part the number of adventurers who attempt Mont Blanc’s peaks every year: about 20,000. That total is more than 25 times the number of climbers who summit the popular Nepal side of Everest, and it includes many novices, some of whom blithely attempt the climb without guides. And then there’s the particularly lethal Grand Couloir.
Ravanel probably understands the dangers and dynamics of the legendary peak’s highest faces better than anyone. The 42-year-old grew up in the town of Chamonix in the French Alps at the foot of Mont Blanc, where for generations his family had plied the range’s granite and glaciers as Alpine guides. As a teenager, Ravanel devoted himself to the southwestern-most corner of the Alps as hobby naturalist, rock climber and mountaineer. And he bagged Mont Blanc for the first time at just 17 years of age, before maturing into one of France’s premier Alpine climbers, one who competed on its national team in the 1990s.
But the climbing deaths of several friends and teammates—and some very close calls of his own—caused him to reflect and sent him back to the classroom. The 20-year-old began studying geology in 2002 at the University of Savoy Mont Blanc, in Chambery, France, before realizing that it was the high peaks’ glaciers and ice aprons—the thin ice on high-altitude faces—that most fired his curiosity. “I fell in love with science,” says Ravanel, a geomorphologist who now serves on the same institution’s faculty. The university is devoted to study of the Alps, one of Europe’s most extensive mountain ranges that stretches across eight countries.
After Ravenel switched to geomorphology, he zeroed in on the way that global warming was altering the conditions and configurations of the Alpine landscape before his eyes. Since then, he has made the impact of climate change on Europe’s loftiest slopes his life’s work. In the last few years, he has noted how rockfalls have soared as global warming melts the Alps’ glaciers and ice fields, altering the mountains’ terrain. The Estonian woman in the video may have been oblivious to it, but she was very nearly a casualty of the climate crisis.
“The whole Alps has been hit very hard by the climate crisis, harder than most places in the world,” says Ravanel, in a somber tone.
“In just 2022 and 2023,” he continues, “Mont Blanc has lost 10 percent of its ice. Since 1950, half of it.”
Ravanel wonders aloud what will be left of Blanc’s glaciers by the time his three children—all alpinists, too—enter adulthood.
A wiry man with an angular face and scruffy beard, Ravanel explains that ice is the glue that holds the upper regions of peaks higher than 8,500 feet, like Mont Blanc, together. When this glue dissolves, the mountains begin to shift and crumble. “The mountain becomes less stable: the glaciers, moraines, ice aprons, rock faces, all of it,” he says.
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The rockfalls on stretches of Mont Blanc have become so hazardous at the height of summer that experienced guides—which Ravanel is, too—refuse to take clients there. In 2022, the mayor of Saint-Gervais, a French village on Mont Blanc’s lower slopes, proposed that thrill seekers pay a €15,000 (around $15,600) deposit before attempting Mont Blanc: €10,000 for rescue operation costs and €5,000 for funeral fees. The idea was that if they made it back in one piece—and not having required an emergency rescue—they’d be reimbursed in full. Little communities like Saint-Gervais struggle to shoulder the financial burden of these kinds of emergency services, he said.
The dynamics at work on Mont Blanc are multiple, Ravanel and his colleagues have ascertained. Glacier crevasses are ever more prevalent as the ice shrinks and shifts. Summit ridges are narrower as once-solid ground erodes. And snow slopes have been transformed into steep, exposed ice as snow melts and refreezes. The University of Savoy Mont Blanc research teams are just now discerning patterns and plotting the frequency of extreme mountain events.
Using high-tech sensors and terrestrial laser scanners, Ravanel and fellow scientists are studying exactly how the temperature is fluctuating and how permafrost reacts to it. Ground that has been frozen for years—perhaps even millennia—permafrost is now warming and eventually melting as temperatures increase. By locating sensors in deep bore holes, the scientists found that the French Alps’ permafrost is warming by 1 to 1.5 degrees Celsius (roughly 1.8 to 2.7 degrees Fahrenheit) a decade. The studies on permafrost degradation and rock slope instability have discovered that warmish water from the melting permafrost, or from rain and snow melt, seeps down into colder rock structures. Pressure builds and fractures the rock, prompting rockfalls and avalanches. And water accumulating at the base of glaciers can actually cause the ice to slide, says Ravanel, noting that this phenomenon has already wiped out mountain huts and bridges.
Ravanel’s published studies—often conducted as part of a larger scientific team—have found 25 geomorphic changes related to climate change that can influence mountaineering. Moreover, rockfalls in permafrost-affected peaks are much more frequent when temperatures rise and snowmelt begins. The scientists found a daily correlation between rockfall frequency and air temperature; on average, only two hours separates temperature rise and subsequent rockfall. Another study shows that on some of the Mont Blanc range’s faces, the annual rock-wall erosion rate of 18.3 millimeters (3/4 inch) between 2005 and 2022 is one of the highest rates in the European Alps. The same team also identified that rockfall between 2016 and 2022 was almost nine times as high as from 2005 and 2014.
But the region’s native son always has the greater Alpine community in mind too—from mountaineers to Alpine village populations. “Even today when I look at a rock face or glacier,” he says, “I think of it first as a mountaineer, and then as a scientist.”
The geomorphologist communicates what he’s learned about Alps as he travels between France, Switzerland and Italy, and presents his findings to outdoorspeople, local officials and schools. The mountains’ transformation is highly relevant to ski resorts, real estate owners, cable car operators, infrastructure planners and backpackers, he points out. For example, the speck-on-a-map village of Brienz in the Swiss Alps, east of Mont Blanc, finds itself in the path of a disintegrating mountainside consisting of 42 million cubic feet of debris. It is periodically evacuated due to rock avalanches that creep steadily ever closer toward it. When experts make the call—based on calculations of the rock masses’ sliding speed—Brienz’s 80 residents pack their kit and decamp, as they did again this year on November 15.
Not all of the geomorphologists who work on Ravanel’s topic—and even work closely with him—understand the scientific research as so intimately linked to the welfare of recreational mountaineers as he does. “We are academics, and our purpose is to study mountains, glaciers, seracs and moraines,” explains Philip Deline, also a geomorphologist at the University of Savoy Mont Blanc. “It’s not our job to give advice to hobbyists. We don’t know enough to say, ‘Use this or that trail.’”
Yet Ravanel’s message for Alpine guides is to respect the research that shows when and where rockfalls are most prevalent, and to constantly reassess the technical ability involved in the routes. Thus far, they have done this, says Jörn Heller, a German guide who knows Ravanel and his colleagues. He is grateful for the scientific research, he says, and factors it into his calculations. “Routes we could take a couple years ago at a certain time of the day now have to be done earlier,” Heller says. “In July and August, some routes, like the Couloir, are simply out of the question.”
The scientists’ input and the guides’ caution, notes Heller, have prevented a rise in fatalities on Mont Blanc.
Ravenel’s research into the dynamics of ice and terrain at high altitudes is abetted by his climbing skills. Recently, Ravanel accessed ice from a Mont Blanc peak that the university’s laboratories calculated as the oldest ever found in the Alpine regions: 6,250 years old.
“In this ice lies the memory of climates past,” he says. “Now it’s melting, which means that the mountain had not had as little ice as it does now for more than 6,000 years. That's the climate crisis.”