Deadly rockfall This is why Swiss mountains are becoming increasingly unstable
The death of former German biathlete Laura Dahlmeier from a rockfall has brought an often underestimated risk into focus: the thawing of permafrost. This is also a silent source of danger in Switzerland.
No time? blue News summarizes for you
- Former world-class biathlete Laura Dahlmeier died in a rockfall accident on Laila Peak in Pakistan.
- Due to climate change, the permafrost, which serves as a stabilizing layer for rocks, is increasingly thawing in the Alps, which increases the risk of rockfalls.
- Measurements show that the permafrost has warmed significantly since 2014.
The news of the death of German former biathlete Laura Dahlmeier has not only caused great consternation in the sporting world.
The two-time Olympic champion, who had announced her retirement in 2019, was hit by a falling rock on Laila Peak in Pakistan on Monday. On Wednesday, her management confirmed that she did not survive the accident. Laura Dahlmeier was only 31 years old.
Every mountaineer knows that the danger of falling rocks is always present when climbing. There are also other natural hazards such as avalanches and debris flows. Dahlmeier herself is already the fourth person from her closest climbing circle of friends to die in the mountains.
One development is also a cause for concern in this country: the thawing of permafrost.
What is permafrost?
Permafrost is permanently frozen ground that covers around five percent of the land area in Switzerland - mostly above 2500 meters. This invisible ice acts as a natural binder that stabilizes rocks and scree.
Permafrost is thawing
For decades, researchers from the Swiss Permafrost Monitoring Network (Permos) have been observing an increasing warming of the permafrost - especially in recent years.
At a depth of ten meters, the permafrost has warmed by an average of 0.8 degrees Celsius since 2014. In the hydrological year 2024, which runs from October 2023 to September 2024, new record values were once again measured. The trend is also clearly visible at a depth of 20 meters.
The causes
One reason for this is that early snow acts like an insulating layer - it protects the ground from cooling down in the fall and thus accelerates the thaw from top to bottom.
In addition, the hydrological years 2022, 2023 and 2024 are among the five warmest recorded in Switzerland since measurements began in 1864. Temperatures were 1.44 to 1.9 degrees Celsius above the average for the period 1991 to 2020.
According to the Swiss Academy of Sciences (SCNAT), the warming of the permafrost is continuing at greater depths. As a result, the layer that thaws in summer and freezes again in winter has also become thicker. It has reached new record levels at all measurement locations.
At the Schilthorn in the Bernese Alps, the thaw layer no longer froze through for the first time at a Permos site in the winter of 2024.
What does this have to do with rockfall?
Permafrost is not a natural hazard. However, when permafrost ice melts as a result of climatic changes, the ground can become unstable - increasing the risk of natural hazards.
This applies in particular to near-surface falls such as falling rocks or boulders. According to the SLF, individual stones with a diameter of less than 50 centimetres are referred to as rockfall. Larger boulders are called blocks.
The permafrost is one of several factors that influence the stability of frozen mountain slopes, explained Jeannette Nötzli from the SLF to the Keystone-SDA news agency in June.
According to the researcher, geological and topographical conditions must also be in place for a major event - such as a rockfall or landslide like the one in Blatten VS - to occur.
