5 October 2016

Aletsch: a major developing post-glacial rockslide

Posted by dr-dave

Aletsch: a major developing glacial rockslide

Both Juy Bullot and Eric Bardou (many thanks to them) have alerted me to a very interesting major rockslide developing in the Aletsch region of Switzerland.  Reports about the slide are only in French as far as I can tell, but this is a most interesting landslide.

The slide itself is at Moosfluh in the Riederalp, Canton du Valais, above the left flank if the Aletsch Glacier.  This is a Google Earth image of the site, although note that the image is seven years old:

Google Earth imagery from 2009 of the site of the Aletsch landslide in Switzerland

Google Earth imagery from 2009 of the site of the Aletsch landslide in Switzerland

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Le Nouvelliste has a brief article on the landslide (in French of course).  this is my translation, with help from Google because I’m lazy!,:

A landslide in Moosfluh on the left bank of the Aletsch glacier has greatly accelerated in recent weeks. The hiking trails in the sector have been closed by the municipality of Riederalp with support from the canton.  Numerous cracks and a few rockfalls have been observed at Moosfluh on the left bank of the Aletsch glacier. The phenomenon is being monitored in detail. The area concerned is about 1 square kilometre. The moving mass has a volume of more than 200 million cubic metres and is moving more than 20 cm per day.

A rapid collapse of the entire mass seems at this stage very unlikely.

They have this image of the site:

Image of the developing landslide at Aletsch in Switzerland, via Etat Du Valais and Le Nouvelliste

Image of the developing landslide at Aletsch in Switzerland, via Etat Du Valais and Le Nouvelliste

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Rhone FM has a view from a different angle:

Aletsch landslide

An image of the Aletsch landslide, via Rhone FM

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This is a wonderful opportunity to study the development of  progressive failure in a large rockslope.  Predicting the time of failure is fraught with difficulty, and it is good that no bold forecasts are being made at this stage.  A particularly interesting aspect of this landslide is that its location is close to the terminus of the retreating Aletsch Glacier.  Wikipedia reports that in some years this glacier is retreating at 100 m per year.  It has long been hypothesised that major rockslides may be more likely when slopes are debuttressed by glacial retreat.  That may be the case here.

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