The Storegga tsunami, caused by the sudden shift of a Scotland-sized section of the seabed off the coast of modern-day Norway, raged across the North Sea approximately 8,150 years ago (see CA 179). Archaeological evidence for this event has been found in onshore sediments across western Scandinavia, in parts of north-east Britain, and even as far away as Greenland. But, although models of the tsunami suggest that it possibly affected parts of the southern North Sea, no concrete evidence for it had been found in this region – until now.
The ‘Europe’s Lost Frontiers’ project, led by researchers from the University of Bradford, is examining the entire evolution of the Doggerland landscape – the strip of land that once connected Britain with mainland Europe, but which is now submerged beneath the North Sea (see CA 314 and 331). As part of the project, the team recovered a series of cores, which they hoped might provide evidence for the Storegga tsunami in this region. Distinguishing between deposits caused by a tsunami versus those caused by a large storm is not a straightforward task, however, so the team used a multi-proxy characterisation, which included geochemical, sedimentological, palaeomagnetic, isotopic, palaeobotanic, and ‘sedaDNA’ (sedimentary ancient DNA) methodologies, to analyse the cores.
This process identified a sedimentary sequence within one of the cores with six layers of unusual deposition, which the team has interpreted as three main tsunami waves. These layers can be grouped into pairs, with the first of each pair showing increased shell content and the second containing land-based content. As the team notes: ‘This pattern is consistent with that of a tsunami event where the wave impinges on the land, depositing marine-dominated detritus, and then retreats leaving an enhanced terrestrial signature, and does so in multiple wave events… This contrasts with the resulting deposits for a storm sequence, which typically only deposits a single sedimentary sequence.’
The palaeomagnetic data appear to confirm this analysis, demonstrating that the provenance of the material from these deposits was markedly different from the sediment deposits both before and after these layers, and was not local to the area. Radiocarbon dating of the shell fragments within the sediment layers, in conjunction with OSL dating, also indicates that these layers were broadly contemporary with the Storegga event. In all, the combined data seem to point to these layers being caused by the tsunami.
Such a large tsunami hitting Doggerland at this time would have had a major effect, as the region had already started to fade into the sea, with the remaining land being extremely low-lying and extending out in an archipelago off the coast of Norfolk. This could have had potentially devasting consequences for any Mesolithic hunter-gatherer groups still making use of the area. But, while it had been previously theorised that the Storegga tsunami may have been the final event that completely flooded Doggerland, this new evidence suggests something different. While the tsunami does appear to have altered the landscape, potentially opening up vegetation and allowing easier access to streams and channels for larger animals, the final inundation did not occur until after this episode.
A paper outlining the results of this project was recently published in Geosciences. It can be read for free online (https://doi.org/10.3390/geosciences10070270). More information about the ‘Europe’s Lost Frontiers’ project can be found at https://lost frontiers.teamapp.com.
TEXT: Kathryn Krakowka.