7 October 2011
There have been some amazing rockfall videos in the past, but this one I think tops them all. This video was apparently recorded at Hells Mount, North cliffs near to Portreath in Cornwall, SW England. It is genuinely astonishing:
A few things to note. First these cliffs are about 100 m high and are formed from Devonian slates, greywakes and siltstones. Thus, they erode very slowly. Second watch, the video for the extraordinary precursory activity – prior to final collapse the whole rock mass is clearly deforming. So although this looks at first sight to be instantaneous, it is probably actually the final stage of a progressive process. Finally, note the weather and the state of the ground. It is sunny – certainly no sign of any rain, and the ground appears to be dry. The amount of dust that the landslide generates suggests that the lower levels are dry too. Indeed the video was posted on 3rd October, which was during the warmest spell of October weather on record in the UK> The sea is calm. Thus, there is no obvious trigger – this apparently is a genuine progressive failure.