Last month, a Swiss village was buried when the mountain above ‘exploded’. The impact of climate change is no longer anecdotal
High above the village of Kandersteg, the Spitzer Stein is on the move. It’s sliding at a rate of 6 to 7 metres a year, mainly in the summer. This is unfortunate, because the Spitzer Stein is a mountain and Kandersteg sits at the entrance to one of Switzerland’s most important railway tunnels.
As much as 16m cubic metres of rock and ice – six Giza pyramids’ worth – could give way at any moment.
When it goes, some of it will cascade directly to the valley floor but much of it will crash into an idyllic lake above the village, like a giant jumping into a bath. “That’s the worst-case scenario, when it all goes at once,” says Prof Jan Beutel of the University of Innsbruck in Austria.
In that event, a wall of water will chase the rockfall down towards the village, sweeping up trees, houses and boulders. It’s unlikely anyone will die, because dozens of motion sensors and years of planning mean evacuation orders will have been enforced well in advance. But the runout could be out of control. Big rockfalls tend to take on lives of their own, experts say, spreading debris over wide areas and shaking the mountains for miles around with the seismic impact of an earthquake.
The Alps are melting, and never faster than now. The permafrost that used to seal the high peaks against the elements is the warmest since records began, the Swiss Academy of Sciences said this month. As it warms, its grip on the mountains loosens, even on peaks such as the Matterhorn. Ice bridges that held rock formations together for thousands of years are giving way.
If a reminder were needed, one exploded like a bomb in the Lötschental valley last month, 5 miles as the crow flies from Kandersteg. Nine million cubic metres of mountain detached from the Kleines Nesthorn and fell a vertical mile to the valley below.
The village of Blatten, once home to 300 people and their cows, was wiped out. One hotel roof remained visible; otherwise even the church tower was buried under millions of tonnes of suffocating brown debris.
The village of Blatten, Switzerland, was almost completely destroyed by a landslide earlier this month
It was a two-stage disaster, says Marcia Phillips of the WSL Institute for Snow and Avalanche Research in Davos. First, the mountain gave way, loading a glacier below with rocks it couldn’t hold. Then the glacier went – slowly at first and then live on YouTube, like a scene from the apocalypse.
It’s still too dangerous to return to the detachment zone for a detailed postmortem, Phillips says. But the next big landslide is only a matter of time. “This is something we are seeing all over the Alps.”
Recent events of note include a 4.5m cubic metre slide off the north face of Piz Cengalo on the Swiss-Italian border in 2017, a “massive rock slope failure” on Piz Scerscen in the Engadin region in April last year (at least 8m cubic metres of rock, snow and ice), and 10 landslides since last October on Mont Vélan, near the Col du Petit Saint-Bernard.
Half of Switzerland’s high mountains are now unstable, Beutel says. The permafrost’s “active layer” – the portion that melts and refreezes every year – is deepening annually as its temperature rises by a degree each decade. Meanwhile the mountains get steeper as the glaciers retreat.
For years, the evidence of more and bigger landslides attributable to climate change was anecdotal. Now it’s proven, thanks partly to an Alaskan study of 40 years of global earthquake data, using AI to sort the seismic signatures of giant rockfalls from the actual earthquakes they resemble. These events peak in number in the late spring and early summer, says Prof Dave Petley, vice-chancellor of Hull University and author of the Landslide Blog. “And they are on a rising trend.”
Look at the Matterhorn from far away and it looks very compact. It’s like a croissant; on the surface everything is falling apart
This has serious implications for livelihoods and tourism in mountainous regions, and for famous skylines. A new paper co-authored by Samuel Weber of the WSL shows how rising temperatures and liquid water where there was only snow and ice contributed to the collapse of a granite pillar on the Matterhorn’s Hörnli ridge two years ago.
The water acts as a “heat shortcut”, carrying heat deep into rock masses that had been sub-zero for millennia. “Look at the Matterhorn from far away and it looks very compact,” Weber says. Up close, “it’s like a croissant; on the surface everything is falling apart”.
Forty miles west, the effect of warming on the mountains is making life more interesting and even more dangerous for climbers. In 2005, the entire Bonatti pillar – a granite wall 700m high – detached from the west face of the Aiguille du Dru in the Mont Blanc massif, crashing on to the glacier below and leaving a feast of new routes for alpinists.
“All mountains are essentially in a state of ‘falling down’,” a pioneer of one of those routes wrote recently. That’s true, Petley says. “It’s just happening much, much faster.”
Photographs: Matthias Schräder/AP, Michael Buholzer/AP
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