What Causes Glaciers to Collapse like the Event That Buried a Swiss Village?

Scientific American

2 days ago

An unstable glacier in the Swiss Alps collapsed this week, sending a deluge of rock, ice and mud through the valley below and burying the village of Blatten almost entirely. Scientists had warned about the possibility of a dangerous event related to the glacier, and village residents had been evacuated days earlier—but the glacier's near-total breakup came as a surprise. One person is reported missing. Government officials initially estimated the debris deposit to be several dozen meters thick and approximately two kilometers long. Making matters worse, the collapse of the glacier, called the Birch Glacier, blocked the flow of the Lonza River, which runs through the valley. As a result, a newly created lake upstream from the debris field flooded an area that has now overflowed into the deposit zone, which could cause a debris flow downstream. As of Friday afternoon local time, officials have reported that the water flow is approaching the top of the scree cone, which is the accumulation of loose, rocky debris.
Why did the glacier break apart?
The glacier's collapse and the subsequent landslide—which was so intense that it corresponded to a magnitude 3.1 earthquake captured by the Swiss Seismological Service —likely arose from a series of rockfalls that occurred above the glacier over the past couple of weeks. The rocks, dislodged because of high-altitude snowmelt, exerted significant pressure on the relatively small glacier, according to officials. Experts are looking into longer-term factors that may have weakened the glacier's stability even before those rockfalls. Christophe Lambiel, a glaciologist who also specializes in high-mountain geology at the University of Lausanne in Switzerland, said on RTS Swiss Television that the rockfalls were linked to climate change. 'The increase in the falling rocks is due to the melting permafrost, which increases instability,' Lambiel said, as reported on NPR.
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How would climate change lead to a glacier's collapse?
New research published on Thursday in Science finds that, under current climate policies, more than three quarters of the world's glacial mass could disappear by the end of this century. In this scenario, almost all small and relatively low-elevation glaciers, like the one in Switzerland, would be wiped out. In a 2024 article for Scientific American, journalist Alec Luhn explained that 'the deterioration of ice and snow is triggering feedback loops that will heat the world even further. Permafrost, the frozen ground that holds twice as much carbon as is currently found in the atmosphere, is thawing and releasing these stores.' Thawing permafrost is not just dangerous because it creates instability, as in the case of Birch Glacier. As Luhn wrote, 'Research has revealed that the permafrost zone is now releasing more carbon than it absorbs, heating the planet further.'
Who is at risk from disintegrating glaciers?
It's clear that the weakening of Switzerland's Birch Glacier was at least partially caused by rockfall. There are other ways in which changes to glaciers are causing risk—and occasional devastation—to people, communities and infrastructure. As a 2023 E&E News article explained, 'At least 15 million people worldwide live in the flood paths of dangerous glacial lakes that can abruptly burst their banks and rush down mountainsides.' These so-called glacial lake outburst floods can be fatal and cause catastrophic damage. 'The deterioration of the planet's snow and ice regions,' wrote Luhn in his 2024 article, 'is costing the world billions of dollars in damages,' according to a 2024 State of the Cryosphere report
What can be done to preserve glaciers—and protect communities?
Giant plastic blankets, gravity snow guns and painted rocks are all potential strategies to slow ice melt in the world's mountain regions. The sound that glaciers make when water is coursing through their icy cracks can be used to predict glacial lake outburst floods—and thus to save lives. There's also a growing sense of reckoning with the fate of the world's glaciers. An essay about the Global Glacier Casualty List, which documents glaciers that have melted or are critically endangered, was also released on Thursday in Science. In it, Rice University anthropologists Cymene Howe and Dominic Boyer write, 'The world's first funeral for a glacier was held in Iceland in 2019 for a little glacier called 'Ok….' Since then, memorials for disappeared glaciers have increased across the world, illustrating the integral connection between loss in the natural world and human rituals of remembrance.'