Scottish Tsunamis

25 Oct 2018

Weather Eye in the Times (of London) a couple of weeks ago had a piece on tsunamis that affected the Shetland Islands (and the Scottish mainland in the first instance). Until this year it was thought the only really big tsunami to affect Britain was the one dated just over 8000 years ago that was blamed on a collapse of the Storegga shelf on the seabed off the coast of Norway. Evidence for this has been found along the eastern coast of Scotland in large deposits of sand and detritus. The shelf system at Storegga was of course all part of the continental shelf area around Britain and Ireland and NW Europe - once dry land (in the early Holocene). What might cause a collapse of a shelf is not so certain but tectonic activity is one possibility or the release of methane (assuming a reservoir of methane existed in the North Sea).  Weather Eye goes on to say that a new study (2018) has discovered evidence of two other tsunami waves - in the Shetlands. These occurred 5000 years ago - and 1500 years ago. The first one coincides with the upheavals around 3000BC (mentioned elsewhere on the News) and the second one of course coincides with the onset of the Late Roman Transgresssion and the low growth tree event dated by Baillie at 536 -45AD. Weather Eye gleaned this information from https://www.dundee.ac.uk/news/2018/research-reveals-secrets-of-shetland-... ... where we are told that scientists funded by the Natural Evironment Research Council have identified sands on Shetland that they say prove additional tsunamis 5000 and 1500 years ago. Sue Dawson of the University of Dundee and Dave Tappin from the British Geological Survey worked to identify what could have caused them, using new seismic technology. Dawson said the deposits, up to 13m above sea level, have a similar sediment character to the sands of the Storegga event. The big question here is what caused the Shetland tsunamis - a landslide or an earthquake. See also http://arp.arctic.ac.uk/projects/landslide-tsunami/