24 July 2014
Askja: a very large volcanic landslide in Iceland
Posted by Dave Petley
A very large an interesting landslide occurred in Iceland on the night of 22nd/23rd July in the flanks of the Askja stratovolcano in Iceland. This is a very interesting event in a number of ways, not least because the volume appears to be large – estimates at present range from about 24 million cubic metres to about 60 million cubic metres.
Images are appearing of the landslide, which is impressive in its scale:
The landslide is estimate to be about a kilometre in width. There is a nice video taken from a flight over the landslide on the RUV website too. The landslide entered the lake at the foot of the slope, generating very large tsunami type waves. A credible witness, Ármann Höskuldsson, who was in the area with a group of students, estimates that the waves were 50 m high.
The cause of the landslide is not clear at present. Some of the articles suggest snow/ice melt, but there is no evidence to support the hypothesis. The slopes on the southern edge of the Askja massif are steep. This Google Earth image of what I think is the site suggests that there may have been previous large-scale landslides on this slope:
There is also evidence of large amounts of erosion, suggesting that the slope may have been steadily destabilising with time. It is entirely possible that this is a progressive landslide with no trigger event.
If the waves were 50 m high then the level of erosion around the lake should be extremely high given the weak materials. I have yet to see any good images of the scour around the lake. This must be a golden opportunity to understand better the generation of tsunami waves by rapid, large landslides.
I think you’re right with the idea of a progressive destabilisation of the slope.
It seems on google earth that some more superficial landslide allready occured in the upper part of the slope, with the opening of large trenches near the crest (can see some snow trapped in them).
Very interesting! Continuous subsidence was reported at Askja caldera during in the last 20 years. Probably this also concurred to the destabilisation.