The Landslide Blog is written by Dave Petley, who is widely recognised as a world leader in the study and management of landslides.
News this morning from Blatten in Switzerland is that the landslide on Kleiner Nesthorn has continued to develop. Blue News reports that:
“The situation in Blatten in the Valais Lötschental remained tense during the night to Wednesday. According to a spokesperson for the Lötschental regional command post, there were further small rockfalls. The pile of rubble on the Birch Glacier had grown.“
“There is still a lot of movement on the Kleiner Nesthorn. A constant rumbling could be heard during the night, said the spokesperson at the request of the Keystone-SDA news agency.”
During yesterday, rockfalls occurred continuously, and it appears that a substantial volume of material has now been evacuated from the site.
Swisstopo has made aerial photography of the site publicly available – the best way to view this is on their visualisation tool.
The Google Earth image below shows the site, with Blatten in the valley and the marker located in the path of the part of the slope that has failed to date:-
There is much interest in the potential behaviour of the small ice sheet – the Birch Glacier – just below the marker on the image above, which has accelerated during this period. Rockfall debris falling onto glaciers can cause a change in their behaviour. Whilst I don’t have full details, the concern is likely to focus on either the glacier destabilising and collapsing into the valley, or a large landslide entraining the glacier to form a rock and ice avalanche.
Neither of these scenarios is inevitable (indeed, very little is truly inevitable at this stage), but they would be at the upper end of the range of severity of potential events.
Melaine Le Roy continues to provide excellent updates on the events via his BlueSky feed. Yesterday morning, he posted this animation of the development of the failure:-
This provides a fantastic illustration of the scale of the landslide that is developing above Blatten.
Finally, AZPost has some amazing footage of “smaller” collapses occurring on the mountain:-
This includes this still of the upper part of the collapsing slope:-
The video shows that there is a long way to go before this event is over.