Heavy Rain and Permafrost: How Climate Change Affects Mountains

Status: 06/16/2023 12:53 PM

In Tyrol, a fragment of a mountain peak, two kilometers long, was broken off by a rockslide. Perhaps the thawing permafrost is to blame. It is not the only phenomenon that makes mountains collapse.

Written by Alexander Brotcher, BR

The force of last Sunday’s rockslide is best seen from the air: the structure of Floghorn Peak in the Tyrolean Silvretta Mountains has fractured. Where everything is still covered in snow and white in June, a hole appears on the dark side, and a group of black rocks flows through the snow like a stream of lava.

100,000 cubic meters of rock fell

The massive landslide may have been caused by the thawing of permafrost in the mountains. Chief Tyrolean geologist Thomas Vigel estimated that at least 100,000 cubic meters of rock fell from the southern summit of the Fleghorn massif near Galtür. According to mountain rescuers, even the summit cross has disappeared.

Vigel said that during a reconnaissance trip, there were clear signs that the disappearance of permafrost in the rock was the cause of the natural phenomenon. “The ice is melting because of global warming, and that’s causing the mountains to collapse,” explains the geologist. “Ice is the glue of the mountains, and this glue is slowly disappearing.”

Melting permafrost causes mountains to collapse

Permafrost permafrost all year round. According to the Helmholtz Association’s Earth and Environment Knowledge Platform, permafrost in Germany is only found in the Zugspitze. Ice in the mountains binds rocks together and also plays a role in rock strength, says Michael Krautplatter, a geomorphologist at the Technical University of Munich.

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Water penetration rocks are also a problem. If a gap melts, water can suddenly penetrate there. The water temperature reaches three degrees Celsius up to a depth of 60 meters under the rock. This dissolution on the water is much faster than on the outside.

In the view of the geomorphologist, this could also be the case at Flüchthorn: water penetrates the cracks, internal pressure increases, ice melts, and landslides occur. “Ten years ago we expected heat to come slowly from the outside through the rock and to melt the permafrost. We now see in the Zugspitze and elsewhere that water suddenly enters areas that we thought were frozen for 30 to 40 years,” says Krotplatter.

Experts: Rockfall and landslides are increasing

Krautblatter and his team are developing early warning systems for the Alpine region, which is particularly affected by climate change. “The glaciers are retreating, the permafrost is retreating, and heavy rainfall is becoming more frequent,” says the geomorphologist. However, you have to provide safety in mountain tourism. “In the past 10 years, we have seen an incredible increase in the critical elevation of 3,000 meters in the Alpine permafrost zone,” says Krautplatter.

This development is very dangerous. “If you’re in the wrong place, there’s no way out,” Krautplatter says. You never know which peak will break next. “No ancestor or anything can tell us that, we only have science,” says the geomorphologist. The landslide in Tyrol shows that more peaks should be observed.

According to experts, the danger of landslides is increasing due to climate change, but there is no reason to panic. “Many developing hotspots in the Alps are known and managed,” says glaciologist Jan Beutel of the University of Innsbruck. In these cases, local authorities warn in time or close the tracks. “But the remaining danger remains,” says the researcher and mountain guide.

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Boulders threaten a Swiss mountain village

The rockslide near Brienz in the Swiss canton of Graubünden, which had been expected for weeks, occurred on Friday night. Huge blocks of rock fell down the slope and only came to rest a few meters in front of the old school of the mountain village at an altitude of about 1,100 meters. The road above the village lies meters under rubble, said Christian Gartmann, a spokesman for the municipality of Albula, to which Prinz is from. “Prince was very lucky,” Gartman told SRF.

In contrast to Fleghorn in Tyrol, there is no permafrost near Brienz. The mountain has been moving there for more than a hundred years. However, the continuing rains of the previous May exacerbated the situation in Brienz. The speed of the rockslide accelerated so much that 80 or so people were taken to safety as a precaution.

There is also a risk of a major rockslide in Bavaria

A large rockslide or even a landslide threatens the Bavarian summit, the Hochvogel near Bad Hindelang in Oberallgäu. At the top of the Hochvogel is a chasm that is getting deeper and deeper. Krutplatter and his team meticulously monitor the summit, and sensors record and report every movement. “The Hochvogel is preparing for a particularly large rockslide,” says the geomorphologist.

Smaller pieces will break all the time at the Zugspitze, but the researchers assume that 260,000 cubic meters of rock will break at Hochvogel. “That’s half the top, which then breaks off, that’s not very common,” Krautplatter explains. Unlike in Switzerland, the nearest towns will not be directly affected by the rocks. However, everyone should be warned in time, especially hikers and mountain climbers.

Heavy rain accelerates rock fall

As in Brienz, there is no permafrost in Hochvogel. The mountain at 2592 meters is too low for that – Fluhorn in Tyrol is about 3400 meters high. It has been known for more than 100 years that Hochvogel breaks. Rock waterfalls are completely normal in the Alps.

The problem: Heavy rains exacerbate the situation here, too. “The Hochvogel moves five, six or seven times faster after heavy rains. And heavy rains are becoming more frequent with climate change,” says Krautplatter. Permafrost and the frequency of heavy rainfall are factors that greatly influence the frequency of rock precipitation. “The only thing we can counter is the rapid development of early warning systems,” says Krautplatter. So that as few people as possible become victims of rock falls or landslides. For a fallen mountain is not always so desolate as last Sunday’s Floghorn.

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