13 July 2021
Diablerets: a very interesting video of a rock topple from the Swiss Alps
On Friday 9 July 2021 a rock topple occurred on the flanks of Le Dôme, a peak above Diablerets glacier in Switzerland. This rockfall was captured on a Go Pro camera by an anonymous skier on the glacier. The video is featured in a news report posted to the 20min.ch website. It is worth a visit – I can only post stills here:-
The scale of this topple is difficult to appreciate – I suspect that it is less large than it appears. On the French version of the story on the 20mins.ch website it is reported to have been 30 metres tall but only 50 cubic metres in volume, which seems surprisingly low.
This is a classic topple, actually in the form of two pillars. Note also the rock debris that falls down the rock face as the pillars rotate away, and the way in which the blocks break up even before impact upon the glacier.
As I have noted previously, high altitude rockfalls often occur in the Spring and early Summer as a result of permafrost melting, and the role of climate change. The warm conditions at Diablarets on the day of the rock topple are clear from the video.
Interestingly, in the French version of the report, the local cantonal geologist is quite dismissive of the event (this is a machine translation):
“It’s good on the Valais side,” confirms Raphaël Mayoraz, cantonal geologist, who went up to see the situation in the afternoon. “It is a pillar about 30m high, or about 50 cubic metres, which collapsed from the small south face of Les Diablerets on a small glacier. A priori it does not represent a danger for people and infrastructures, except perhaps for mountaineers. The event is spectacular but relatively minor in terms of volume and impact. This does not give a clearly visible change in the morphology of the terrain. ”
The geologist indicates that the explanation is to be found on the side of the natural erosion of the massif, and the rains of recent days. “There is no trace of ice, which is unrelated to the melting of the permafrost. The overnight freeze / thaw hypothesis is plausible, but difficult to prove. The event is also not linked to climate change and in my opinion the retreat of the glacier has no direct impact on the instability of the cliff. ”
Bold statements indeed!
Many thanks to Martin Luethi for the heads-up on this one.