24 July 2014
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.