20 July 2012

Friday fun: So how does a landslide generate a tsunami? An amazing video of a collapsing glacier

Posted by Dave Petley

Landslides are a key mechanism through which localised tsunamis can be generated, but it is very difficult to actually visualise this process.  An amazing video has just appeared on Youtube that shows this process very clearly.  The video is actually of a collapsing glacier in Greenland, shot from a boat.  The event occurred at Ilulissat:

Obviously the main interest here is in the generation of the waves. The speed and violence of the waves is quite awe-inspiring given that the collapse is not huge.

However, there is an additional aspect of this that is interesting.  This is the way in which the glacier behaved prior to the collapse.  Note that the video shows that the mass was generating small failures in the seconds leading up to the collapse, and that the rate of these increased just before the final failure.  An example is highlighted below:


Similar behaviour is also seen for rockfalls and landslides, and is an indication that the creep rate is increasing, causing the mass to deform, which in turn pops off these little failures.