Experts have warned that a mega-tsunami could put coastal towns across the UK at risk in the future. The event could happen at any time with as little as just six hours' warning, an expert has said, however chances of one happening in the near future seem pretty slim.
Former Chief Scientific Advisor to the UK government, Sir David King, has said that a massive wall of water could be sent crashing into the UK, likely triggered by a landslide in the Canary Islands. He adds that a tsunami, several metres high, would be sent our way, putting many cities in and beyond the coastline in its path.
He told MyLondon that it would take around six hours from the time of the landslide in the Canaries, for the wave to reach the UK. He also spoke of previous cases in other countries where people had much longer to flee, however many people still died, adding that in bigger cities like London many people would flock to their cars to escape, blocking the roads and potentially trapping people in.
Read more: City at risk of being wiped out by ‘megatsunami’ warns Bristol professor
Which cities could be hit by the mega-tsunami if it were to happen?
The list of cities said to be hit by the mega-tsunami so far include:
- Brighton
- Bournemouth
- Exeter
- London
- Portsmouth
- Southampton
But Sir David King explained that in the case of tsunamis, 'the shallower the waters are, the larger the wave will get'. Once the tsunami passes through the English Channel and into the Thames Estuary, it will grow in size and cause destruction in the city. The same is true for the Bristol Channel, meaning locations along the North Somerset coast will also be hit.
What is a mega tsunami? And how is it different to 'normal' tsunamis?
According to SMS Tsunami Warning, a mega-tsunami is described as "an extremely rare and destructive phenomenon that strikes the world every few thousand years. A mega-tsunami has almost unlimited power to cause utter destruction and there's nothing we can do to stop it.
"A mega-tsunami is an informal term to describe a tsunami with initial wave amplitude (height) much larger than usual tsunamis. Mega-tsunamis are several tens, hundreds, or possibly thousands of meters high and they are able to cross oceans and ravage countries on the other side of the world.
"Generally, a tsunami is caused by an earthquake near the shore or underwater. Normal tsunamis usually originate from offshore earthquakes, submarine landslides and undersea volcanic activity, and range from barely perceptible waves to walls of water up to 300 feet high.
"The biggest submarine earthquakes can shift the ocean bed up or down by around 10 metres and that produces tsunamis on that sort of scale, but not very much bigger. Normal tsunamis created by an earthquake on the ocean floor have only small wave heights while offshore.
"They also have a very long wavelength (often hundreds of kilometres long) and they generally pass unnoticed at sea, forming only a slight swell usually of the order of 30 cm (12 inch) above the normal sea surface. However, the height of normal tsunami waves increases dramatically when they reach land as the base of the wave pushes the water column on top of it upwards.
"By contrast, something massive is needed to create waves with such a great height in the case of a mega-tsunami. Unlike usual tsunamis, mega-tsunamis are caused by giant landslides and other impact events such as volcanic eruptions or huge asteroids crashing into the sea. These phenomena rapidly displace large volumes of water, as energy from falling debris or expansion is transferred to the water."
What Sir David King says
Sir David King told MyLondon: “After the landslide in the Canary Islands, it would take roughly six hours for the wave to reach the UK. That might sound like a long time to give people to escape, but there are other places where people had longer to flee yet many people still died.
What would happen in London is that everyone would get into their cars all at once to escape the city and they’d block all the roads. People wouldn’t be able to get out in time and they would essentially die in their cars.
"In the case of tsunamis, the shallower the waters are, the larger the wave will get. Once the tsunami passes through the English Channel and into the Thames Estuary, it will grow in size and cause destruction in the city.
"It could happen in 10,000 years time, but it could also happen tomorrow.” The former Professor of Chemistry at the University of East Anglia compared what would happen in London to what happened in Lisbon in 1755.
The Portuguese capital was hit by a wave up to 10 metres high following an earthquake estimated to have had a magnitude of between 8.5 and 9 on the Richter scale, killing up to 100,000 people. As well as potentially killing a significant amount of people and making families homeless, the scientist also warns of the ecological consequences of a tsunami.
He added: “Salt water coming in from the sea could contaminate some fresh water reserves." He added: "There would be some ecological damage to wildlife too.
“On that note, the salt water would also saturate the soil around London. The change in salinity levels would mean farmers wouldn’t be able to grow crops in the area for many years afterwards, as has been seen in other tsunami-affected regions.”
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