Evidence for three North Sea tsunamis at the Shetland Islands between 8000 and 1500 years ago

Abstract

Coastal fen-and lake deposits enclose sand layers that record at least three Holocene tsunamis at the Shetland Islands. The oldest is the well-known Storegga tsunami (ca 8100 cal yr BP), which at the Shetlands invaded coastal lakes and ran up peaty hillsides where it deposited sand layers up to 9.2 m above present high tide level. Because sea level at ca 8100 cal yr BP was at least 10-15 m below present day sea level, the runup exceeded 20 m. In two lakes, we also found deposits from a younger tsunami dated to ca 5500 cal yr BP. The sediment facies are similar to those of the Storegga tsunami-rip-up clasts, sand layers, re-deposited material and marine diatoms. Runup was probably more than 10 m. Yet another sand layer in peat outcrops dates to ca 1500 cal yr BP. This sand layer thins and fines inland and was found at two sites 40 km apart and traced to ca 5-6 m above present high tide. The oldest tsunami was generated by the Storegga slide on the Norwegian continental slope. We do not know what triggered the two younger events.

Prehistoric Coastal Mass Burials: Did Death Come in Waves?

“…It has similar sedimentary characteristics to the 8150-year BP Storegga tsunami and probably had a runup of more than 10 m (Bondevik et al 2005b). The 5500-year BP Garth tsunami (hereafter called the 5500 BP event) was initially found in Sullum Voe and then at two lake basins (Garth and Lake of Benston) on the eastern coast of Mainland (Fig.…”

“…There is also evidence on Shetland for a more recent tsunami that affected the area around 5500 years BP (Bondevik et al 2003(Bondevik et al , 2005bDawson et al 2006;Ishizawa et al 2016). It has similar sedimentary characteristics to the 8150-year BP Storegga tsunami and probably had a runup of more than 10 m (Bondevik et al 2005b).…”

“…This event could represent a later (and smaller) submarine slope failure from the Storegga area or may be related to the Afen slide about 120 km NW of Shetland ( Fig. 1) (Bondevik et al 2005b;Haflidason et al 2005;Long et al 2003). The Afen slide occurred sometime after 5800 years BP, but its volume (0.4 km 3 ) was probably too small to generate a tsunami of any size (Bondevik et al 2005b).…”

“…1) (Bondevik et al 2005b;Haflidason et al 2005;Long et al 2003). The Afen slide occurred sometime after 5800 years BP, but its volume (0.4 km 3 ) was probably too small to generate a tsunami of any size (Bondevik et al 2005b). However, more recent work has found that comparatively small submarine slope failures (i.e.…”

Mass Transport Events and Their Tsunami Hazard

“…The lack of evidence may, however, be more apparent than real. In other territories, such as open continental slopes and canyons, fjords, convergent margins and volcanoes, there is significant evidence that mass movement can result in hazardous, if not, devastating tsunamis; such as at Mt Unzen in 1792 (Siebert et al 1987), PNG in 1998 and Storegga at 8,200 years BP (Bondevik et al 2005).…”