Around 8000 years ago near Norway, an area of the sea-floor around 600 km long collapsed. The Storegga Slide generated a tsunami that struck Norway, the Faeroes, Shetland, Scotland and north-east England. The waves that hit Shetland reached areas 20 m above sea-level. In both Scotland and Norway the sand left by this tsunami lies on top of Mesolithic settlements, but how much were people of the time impacted by this natural disaster? Determining this falls down to knowing the time of year: if it were the spring or summer Mesolithic people would be inland hunting deer; however, late autumn of winter was when Mesolithic groups relied on sea food for sustenance. Well it appears that Mesolithic people may well have been on the coast when this tsunami hit. Growth details on moss preserved in the tsunami deposits shows that it occurred late in the year and thus when Mesolithic people relied on coastal food sources.
The Storegga tsunami, triggered ∼8150 yr ago by one of the largest submarine slides on Earth, flooded margins of the North Sea and the Norwegian Sea that were occupied by Mesolithic peoples. Sand deposits of Storegga age overlie the remains of coastal settlements in Norway and Scotland. The resulting casualties, however, depend on the season when the tsunami struck. Human exposure would have been least in summer and early autumn, when Mesolithic peoples went to the mountains to hunt reindeer. The hunters returned to the coast in late autumn to settle into their winter quarters.