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March 15, 2011

Tsunami: Wave of Terror?

Why cruise ships are safe from tsunamis

One could be forgiven for thinking that the doomsday prophets are going to have their day with the recent roll of disasters sweeping our planet. Japan, a country used to and quite probably the best prepared in the world for such an event, was brought to its knees. And the story is far from over.

But what for cruising? What if you are caught at sea during a tsunami warning? Will you become an unwilling extra in the next Poseidon Adventure?

For film and cruise buffs, the Poseidon Adventure (1972) was developed from a 1969 novel and spawned three sequels; 1979, 2005 and 2006. But the basic premise of the ship (any ship) being capsized by a mid-ocean tsunami is seriously flawed. In the original movie, it was indeed an earthquake that supposedly sent a 50 metre wave rolling across the ocean casually overturning ocean liners in its way. Tsunamis don’t do that.

Tsunamis travel at high speed, up to 800kmh with a very low wave height, from the undersea quake’s epicentre. Like the ripples created from a stone tossed into a pond, the nasty breaking waves only occur when the energy meets a solid object, like a coastline or shallow water. Because the ‘wavelength’ is long, the energy just keeps on coming and drives water way inland as we saw on Japanese TV.

So, as evidenced by the complete lack of damage to cruise ships at sea during the massive 8.9 earthquake, you can safely ride out a tsunami at sea and probably not even notice it.

A ‘rogue wave’, however, is a different kettle of fish altogether and still has scientists discussing the origin and cause. Yes, ships need to worry about rogue waves.

Several cruise ships have encountered them. In 2001, Bremen and Caledonian Star were both surprised by a so-called freak wave of 30m in the Drake Passage, perhaps similar to the one that damaged Clelia II last December. QE2 hit one mid-Atlantic in 1995 during a hurricane and the original Queen Mary was whacked broadside by one while carrying thousands of troops in 1942. She listed to 52 degrees, damn near capsized and gave novelist, Paul Gallico, a highly profitable idea.

In 1966, a rogue wave struck the
giant Italian liner Michelangelo.
Some waves can be predicted by currents, sea floor and weather, such as near South Africa’s Agulhas Current, but the so-called ‘perfect storm’ conditions can produce what wave mathematician, Al Osborne, calls ‘unstable non-linear monsters’. These are the real whoppers that feed off adjacent waves and rise up to absurd proportions.

The only passenger ship thought lost due to a rogue wave was the 1909 disappearance of SS Waratah off South Africa. Her wreck was never found.

So unless, you are sailing headfirst into a cyclone, there is little worry you will encounter one of these waves and as for tsunamis, you have more to fear from lightning strike or crossing the road. Cruising remains one of the safest forms of transport, true.



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