Scientists move closer to source of tsunamis in Shetland Islands

About 8,200 years ago, the Storegga submarine landslide off Norway caused a 20-meter-high tsunami that swept the Shetlands. The sands found in various points of the islands and in mainland Scotland, Norway, the Faroe Islands and Greenland proved the height of the tsunami and the event was well reported.

NERC-funded scientists have identified sands on the Shetland Islands that they say prove that additional tsunamis struck the Shetland Islands 5,000 and 1,500 years ago. This could mean that tsunamis are more common than we thought in the UK.

Dr. Sue Dawson of the University of Dundee and Professor Dave Tappin of the British Geological Survey (BGS) are working to identify what might have caused these tsunamis, using the new CT and seismic technology.

Dr. Dawson said:

We found 5,000 and 1,500-year-old sands at different locations in the Shetland, up to 13 meters above sea level. These deposits have a similar sedimentary character to that of the Storegga event. can be related to floods caused by the tsunami. We are now using a scanner at the University of Dundee to examine our samples in detail.

For the first time, we will have a complete 3D view of the cores we extracted from the soil, lakes and seabed. This detail will tell us in which direction the wave was moving, identify the elements present in the sand and much more. This will be the first time that such a level of detail has been captured during these prehistoric events.

Both scientists agree that an underwater landslide, which is an underwater landslide that displaces large amounts of sediment on the seabed, has generated the tsunamis that have hit the Shetland Islands.

While Dr. Dawson was investigating the sand samples, Professor David Tappin focused on the seabed to try to determine the origin of the tsunamis.

Professor Tappin of BGS said:

The seas of the youngest tsunamis on the Shetland Islands are located quite close to each other. So we thought that the underwater landslide could be very close to the shore. The BGS White Ribbon Research Vessel, which can operate in the shallower waters, has been used for seismic surveys of the seabed around the Shetlands, but we have yet to find conclusive evidence of landslides under -marins.

The identification of landslides on and under the seabed using existing mapping methods is not as simple as one could imagine. We plan to test some theoretical models to see if we can replicate the 1,500 and 5,000 year tsunamis.

We will create a digital elevation model of Shetlands coasts and surrounding seabed. We will then reproduce the landslide movement that will generate the tsunami. The digital model will flood the earth and we will examine the elevation of the sediments to see if they match those of the Shetlands. This will take us much further to find where the tsunami really started.

Underwater landslides are much less well understood than almost all types of natural disasters, such as river floods or storm surges. But they can be much larger than any landslide observed on Earth – the Storegga slide contained 300 times the amount of sediment transported annually by all the rivers in the world combined.

Underwater landslides can also occur on slopes of only one or two degrees, and we still do not know exactly how they are moving, except that earthquakes are considered the most common trigger. It is essential that we learn more.

The research is part of the Landslide-Tsunami project, an ongoing research that is a key component of NERC's Arctic research program. The project aims to discover the causes of huge underwater landslides, the impact of slips in different locations and their magnitude on the UK, and the likelihood of such an event, given the magnitude of the changes. in the Arctic.

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