2 February 2021
Kapuche Lake, Nepal: a video of an avalanche air blast
Large landslides generate substantial air blasts, which can be extremely damaging. There are some studies of this phenomenon; a classic example was generated by the 2015 earthquake in Nepal, when Langtang was destroyed at least in part by an air blast. The effects were terrible (take a look at the images in that post), but this is an under-researched area.
I don’t normally feature snow avalanches on this blog – there are others who know this topic far better than do I, but there is a very interesting video on Youtube showing an avalanche at Kapuche Lake in Parche, Nepal. This was a very large and very impressive event – the video is worth viewing simply for the scale of the avalanche. The avalanche itself starts at 1 minute 01 seconds:-
But the really interesting (from my perspective) element of this video is when the avalanche reaches the lake, from about 2 minutes 50 seconds. Stripped of the slope gradient, the avalanche appears to lose energy and indeed it is clear that the group making this video were not concerned. But moments later the air blast reaches them:-
The initial moments of the air blast are quite dramatic and clearly unexpected. This is followed by a few minutes of intense wind, driven by the mass that has descended from the peak. The event is over in a few minutes.
The intensity of the air blast is notable, but the volume of snow and ice that has descended is small compared with a large rock and ice avalanche. It’s hard to imagine the intensity of an event such as the one at Wenjia in Sichuan Province, triggered by the 2008 Wenchuan earthquake in China.