13 July 2021
Diablerets: a very interesting video of a rock topple from the Swiss Alps
Posted by Dave Petley
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 rock topple above Diablerets glacier in Switzerland on 9 July 2021. Still from a video posted to the 20mins.ch news site.
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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.
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
I looked for it on the swiss geoportal and found traces of another rockfall of comparable magnitude, which might be a few tens of meter to the east : https://map.geo.admin.ch/?topic=swisstopo&lang=en&bgLayer=ch.swisstopo.swissimage&E=2582035.15&N=1129200.60&zoom=12 😉
It does not seem to me that these kind of phenomenons (of small scale in this context, indeed) are exceptional, but having the fall itself on video is always interesting!
“The event is also not linked to climate change”…
??????
A very bold claim for a geologist to make, as you say. I’m sure Mr.Mayoraz also can put as at ease on the origins of the coronavirus, and await his pronouncements eagerly!
Give that geo a cigar, a very level headed synopsis.
Mr Mayoraz has been to the site and given his opinion as a geologist. If Mr Johnson has an alternative explanation let us hear it.
Whatever this rock fall event, large or small, related or unrelated to climate change, it has already taken place!
Far more important would be to know how this type of events could be forecasted BEFORE it happened!
Is it possible to monitor vulnerable areas by satellite imagery, field work, flying surveys, etc. searching for weakness zones, precursor widening fractures, etc.?
Luckily, the area was inhabited. Otherwise, the results would have been catastrophic!
We have some good results, recently, detecting a large fracture in volcanic cliffs that consequently resulted in a rock fall in the Canary Islands.
Interesting to read how even educated scientists (both the geologist and the commenters below this article) are very quick to give a firm opinion on a very basic observation that lacks any quantitative measurements.
Looking at the official swiss map (map.geo.admin.ch) showing the spatial distribution of permafrost, this site is only marked with “permafrost possible, locally, discontinuous, punctual”, meaning that it is not certain at all that there was any permafrost that could have persisted in that rock pillar before it collapsed (it is a south face located at only 3000 m.a.sl., after all!). Glacial debuttressing could be a possible contributing cause though.
But let’s remember that it is quite normal for (especially fragile) rock features to collapse from time to time – with or without global warming. Of course such events are becoming more frequent with global warming, but this does not mean that they did not occur already before anthropogenic influence on the climate started.
Regarding climatic conditions on the day of the event, you can see the freshly fallen snow in the video. For a mid-summer day temperatures were actually not warm at all – the reason why the person who filmed it went up there for skiing (an unusual thing in July in the Alps).
Hello Pascal, Please don´t include me in your list. I don´t fit the bill. I am a geologist and I have proposed monitoring and collecting information from different sources in vulnerable areas for damage prevention (see above). Thank you!