Poster De Conférence Année : 2025

On the contribution of permafrost and its degradation to the Blatten disaster (Swiss Alps)

Résumé

On 28 of May 2025, a rock-ice avalanche originating from the Kleines Nesthorn (3,342 m a.s.l.) and the Birch glacier devastated the village of Blatten in the Lötschental (Swiss Alps). The disaster was caused by the rapid acceleration of a deep-seated rockslide on the northern slope of the Kleines Nesthorn in early May, which triggered a sequence of rockfalls from mid-May onward that accumulated on the upper part of the Birch glacier. Intense rockfall activity over the past three decades had gradually covered the glacier with debris, limiting its melting and increasing its flow velocity. As a result, the glacier front advanced by approximately sixty meters over the last fifteen years, which is highly unusual on an Alpine scale. Already topographically unstable, the glacier eventually collapsed under the weight of the debris. 9 million cubic metres of debris (6 M) and ice (3 M) buried the village of Blatten and the valley floor below the village, completely transforming the landscape. We present here : • different documents showing the initial topographical and glaciological situation, • assessment of permafrost conditions at the Kleines Nesthorn, • the installation of a surface temperature sensor network • first conclusions on the contribution of the degradation of permafrost to the disaster

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Dates et versions

hal-05375095 , version 1 (20-11-2025)

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Identifiants

  • HAL Id : hal-05375095 , version 1

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Christophe Lambiel, Ben Robson, Florence Magnin, Ludovic Ravanel. On the contribution of permafrost and its degradation to the Blatten disaster (Swiss Alps). International Moutain Conference, Sep 2025, Innsbruck, Austria. . ⟨hal-05375095⟩
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