Tidal wave or mere ripple

PICTURE the scene. A giant wall of water the height of a threestorey- house looms on the horizon as it powers across the English Channel at 500mph.

Within minutes the awesome tidal wave has hit the southern coastline like a steam roller mercilessly blasting through buildings, ripping up trees and killing thousands of people in its destructive wake.

Even after the first wave has struck the turbulent waves keep hammering on the shore building up momentum until the water starts to drain and pull backwards dragging everything in its swirling mass out to sea - cars, houses and drowning human beings.

There would only be a five-hour warning.

Then the ten metre wall of cascading water would flood the historic heart of the city as well as the residential areas bordering the River Itchen and Test.

Southampton docks, of prime importance to the UK economy, would also be flooded together with the communities of Freemantle, Millbrook, Redbridge and beyond.

It sounds like something out of blockbuster movie The Day After Tomorrow - but this scenario could prove more than just a fairytale to people on the south coast according to top scientist Professor Bill McGuire.

The director of the Benfield Hazard Research Centre at University College London warned that a tsunami of this scale will strike and cause devastation in the future.

He claims that it is only a question of when and not if it happens - and the balance lies on a time bomb slab of unstable rock moving on the side of Canary Islands volcano, Cumbre Vieja in La Palma.

When the volcano next erupts, there is a chance that the 12-mile slab will break off and cascade into the sea in a matter of minutes with significant enough impact to affect southern England, the Caribbean and the eastern coast of the USA.

Scientists at Southampton Oceanography Centre have criticised the professor for unnecessarily worrying the public with what they feel is a worst case and unlikely scenario.

They believe the rock is unlikely to tear off in one go which in turn would reduce the effects of any tsunami hitting the UK.

But Professor McGuire insists: "This rock will collapse into the sea but we don't know when.

"It could happen when the volcano next erupts or 20 eruptions down the line - but it will happen and when it does it will happen quickly."

At least 20 years separates each eruption and the last happened in 1971.

The predictions of what happens afterwards have been modelled using computers - though Professor McGuire concedes they haven't been specifically modelled for the possible impact on the UK yet.

But nevertheless he claims the tsunami waves would hit the south coast - including the Isle of Wight, Southampton and Portsmouth within five to six hours of the rock's impact in the Atlantic.

He said: "These would be focussed in the estuaries and harbours in the area and could get bigger. "If you can imagine waves of ten metres high coming for five minutes or so that is very destructive.

"The waves will break up but they have a long wave length from one end to the other - they will keep on coming in a train of maybe up to a dozen.

"They wouldn't penetrate vast distances inland - possibly up to one kilometre. A few streets would be affected - the first few blocks.

"But then the water would drain back the way it came - any people or structures caught in the water would be taken out to sea. The death toll would be significant if people were not evacuated."

But experts at Southampton's Oceanography Centre immediately reassured local communities and said there was no cause for concern.

They claim this scenario is based on computer models and experiments with bricks in a tank that do not fit with historical evidence.

Marine scientist Dr Russell Wynn is going out to the Canary Islands later this year to research the ocean bed around the volcano.

He is part of a team who have 20 years experience in the Canary Islands and said: "I certainly wouldn't lose any sleep over what will happen. We are government funded and are not a biased group - we're happy to give a balanced view.

"I think it's irresponsible not to give people all the facts about what could happen.

Professor McGuire has gone right to one end of the spectrum.

"There have only been two mass landslides like the one he predicts in the last 200,000 years.

"There is more chance of a freak storm or asteroid hitting the south coast of England.

"If a tsunami did reach the UK we believe it would dissipate on the immediate coastline and beaches with consequences more like a fierce autumn storm.

"People certainly wouldn't die unless they were on the beach and got swept out.

The situation may be more grave in the USA with waves reaching buildings and then dissipating but it certainly wouldn't be like anything from a film."

Meanwhile Professor McGuire is standing firm.

He said: "If people were not evacuated from the south coast of England in the event of the tsunami then up to hundreds or thousands of people could die depending on the population.

"Certainly the East Coast of the USA would be devastated. This is a certain event. It's a matter of how we cope with it and not whether or not its going to happen."

Timebomb ready to explode

THE debate on whether or not this tsunami will happen is based on when and how the ticking time bomb 12-mile slab of rock at the western flank of the Cumbre Vieja will tear off and plunge into the sea.

According to Professor McGuire's doomsday scenario, there is evidence to suggest that the rock will break away in one complete segment.

But Dr Russell Wynn, Southampton's Oceanography Centre scientist, said looking back over the history, and that there have only been two huge events on this scale in the Canary Islands in 200,000 years, the chances are one in 15,000 that it will break off in one go.

He said: "Professor McGuire is looking into the future rather than making predictions on what has happened in the past.

"Looking at previous form a landslide on this scale is more likely to happen thousands of years in the future when we are all gone."

But Professor McGuire disagrees with Dr Wynn: "With respect he is not a volcanologist. This is a massive rock which is already on the move.

"I don't think it's likely to happen in stages. There is evidence to suggest it will collapse rapidly. I think it will go in minutes and at that speed the impact will be massive."

Hampshire County Council emergency planning officer, Ian Hoult said that the region had a comprehensive flooding contingency plan which was fully rehearsed with shoreline districts, unitary authorities and neighbouring counties in June this year.

"We are responsible for localised flooding and would respond if a tidal wave caused flooding along the coast."