The British Tsunami

A few weeks ago I mentioned about Mega-Tsunamis and there was a TV show that looked at how an eruption of the Cumbria Vieja volcanic ridge on the island of La Palma will cause a huge mega-tsunami across the Atlantic. This eruption would cause very high waves to expand across the Atlantic, affecting other canary islands, the African coast, the Portuguese coast as well as the East coast of America. It also mentioned how here in the UK we could experience a tsunami from this eruption, though it would be somewhat smaller and affect the southern coasts. The likelihood of this happening however is generally small, though the Cumbre Vieja volcano is due an eruption and when it does blow it will pose a significant threat to the areas in the way of the waves and be a global catastrophe.

 

Tsunamis in Britain are uncommon as there are not many things around us to trigger one. We are away from any plate margins, meaning we are away from anywhere which will cause earthquakes. We are also of considerable distance from volcanic eruptions which could trigger a tsunami. However, there is a few other causes of tsunamis which have triggered waves that have hit the coasts of the British Isles in the past. A Meteotsunami is something we have experienced before, it is a tsunami-like wave of meteorological origin. However, these are generally smaller and are better described as a storm surge. They form from pressure differences due to air-pressure disturbances as storms and low pressures pass over. The height of these are generally only around 1m in height.

 

There have been numerous tsunamis recorded through the decades, in 1014, 1580, 1607 and 1858 there were reports of coastal flooding and some large waves, however, these cannot be confirmed and were not large in nature. In 1755 however, there was an earthquake in Lisbon which caused a tsunami which hit the coast of Cornwall with 3m high waves. They took 4 hours to reach the UK and there were reported to have been 3 waves. Though no official documentation of death there were reports of some along the Cornish coasts.

 

Japan Tsunami 2011

 

 

The largest Tsunami to hit Britain however, was much higher, reaching wave heights of 6m+. This was not in modern times, but evidence we can see today, by looking at sediment deposits and erosional platforms show that there had been a significant tsunami during the Mesolithic period 8000 years ago. It is thought that some of the waves washed over some of the Shetland Isles. Tsunamite, a deposit left by the waves in places is 0.6m thick and has been dated to around 6100BC. At the time the East coast of England was connected by a land bridge to Denmark and the Netherlands, so there is no evidence found here. However, the coast of this land bridge would have been inundated. This Tsunami was caused by an underwater landslide off the coast of Norway. This is an area which had seen large ice sheets removed after deglaciation over 1000years and may have made the sediments underwater become unstable due to the weight loss of ice. They are very uncommon but do underwater landslides pose more of a threat for the British Isles?

 

Find out more about the Scottish Tsunami tonight at 8pm on Channel 4.