4 January 2014
Context of the Hastings Rockfall
The context of the Hastings Rockfall is that over the last few weeks the UK has been suffering the effects of a series of exceptional low pressure systems that have swept in from the Atlantic, bringing heavy rainfall and very strong winds. Unfortunately, the onslaught continues today. The consequence has been high levels of damage (and a political fuss about funding for flood defences), and (unsurprisingly) many landslides.
The Hastings Rockfall event
Perhaps the most spectacular event captured on video to date occurred at Rock-A-Nore in Hastings in East Sussex. Most of the coverage (e.g. the Metro and the BBC) has featured the Youtube video below, but in fact this is not the best one:
If you look carefully at the above video you will see that before the collapse there is a fresh scar on the cliff face. This is because the above event is the second collapse in the sequence. The first was also captured on video and is on Youtube:
The second collapse was also captured by the same person, although this video is less good:
Three aspects are interesting here. First, without the videos we would probably have considered these collapses to have been a single collapse. One of the things that the run of videos is doing is the highlight the sequential nature of failures. Second, a simple before and after analysis would have led to the interpretation that these collapses were simple rock topples, but in fact the mechanism of failure is very complex, in the case of the second set of collapses perhaps driven by compressional failure of the foot of the failing block. And third, the reason that the videos were being captured is that there was precursory rockfall activity.
Background information on the location of the Hastings Rockfall
For those interested in the location of the Hastings Rockfall, the Discovering Fossils website has a good description of the geology of the cliff, which includes this photograph taken before the collapse: