Submarine landslides can generate potentially very damaging and widespread tsunami. For example, the Storegga Slide that occurred 8,200 years ago offshore Norway is larger than Scotland. It produce a major tsunami that ran up to heights of up to 20m around surrounding coasts. A repeat of this scale of landslide-tsunami is one of the most damaging natural events that could impact the UK.
A first important result of our study is that an even larger landslide has been found below the Storegga Slide. This older event occurred at 55-60,000 years ago. Therefore, megalsides in this area have recurrence intervals of less than 100,000 years. This is important because events with recurrence intervals of less than100,000 years should be considered on the UK National Risk Register, and in the design of nuclear power stations.
A second key result originates from dating the Traenadjupet and Nyk Slides located further along the Norwegian Margin, to the north of the Storegga Slide. It was previously thought that we would need another glacial advance to the shelf edge, to dump more sediment, and thereby cause a new landslide. However, our work on the Traenadjupet and Nyk Slides shows that they occurred within 15,000 years, without another ice stream advance. This shows that we do not need another ice stream advance to cause another large submarine slide from the same source area.
Finally, we show that the Traenadjupet Slide did not create a major tsunami along the nearest coastlines. This suggests that not all very large submarine slides are strongly tsunamigenic.