3.4.2 Storegga tsunami

A composite image of satellite imagery and maps illustrating different models of past sea-level

These maps highlight the variety in current models of past sea-level. In order to improve upon these and to help develop predictive models of site survival more high precision data is required. This can be achieved in partnership with other sectors (particularly the energy and aggregate industries) and as part of international projects, such as current work on Doggerland (Gaffney, Thomson and Fitch 2007

One of the world’s largest submarine slides with a total volume of c. 5,600 km3 occurred on the continental slope west of Norway. Part of the sediment complex, with a volume of c. 1700 km3 is believed to have moved as an underwater landslide approximately 7300–7200 radiocarbon years ago (i.e. at c. 8110 ± 100 calendar years BP/6160 ± 100cal BC; Dawson et al. 2011). This occurred ‘near the end of a period of extreme cold climate’ resulting from the 8.2 ka event mentioned in section 3.1 above (Dawson et al. 2011, 1170). The sudden movement of sediment across the Norwegian continental slope and onto the abyssal plain of the Norwegian Sea generated a large tsunami that was propagated across the North Atlantic and Norwegian Sea regions (Dawson et al. 1988). The tsunami affected an area of coastline over 600 km long and deposits have been discovered at numerous coastal locations in western Norway, Greenland, Scotland (including Shetland and Orkney), the Faeroe Isles, and as far south as eastern England (Dawson and Smith, 2001; Bondevik et al. 2003; 2005; Smith et al. 2004).

Isobase models estimate contemporary sea surface level offshore at c. 14 m below the present day mean high water spring tides. Geological studies of coastal deposits in Scotland and Norway attributable to the tsunami indicate that the tsunami runup exhibits strong local and regional variability. In parts of the Shetland Isles, the runup at the coast may have been as much as between +25/+30m above sea level. The tsunami sediments identified in coastal localities are considered particularly valuable as a synchronous marker horizon.

Given the prevalence for exploitation of the coastal zone at the time this event is likely to have been catastrophic for the human population in part of Scotland.

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