many bells down


The only thing that scares me more than spiders.
February 28, 2006, 5:58 pm
Filed under: Science

mega-tsunami.jpgI took two geology courses my junior year of college, and I loved them.  Specifically my environmental geology class, where I learned how tornados, hurricanes and tsunamis formed.  I was so fond of tsunamis that every time I got drunk, I’d inform everyone around me – at the bar, on the street, on the bus as we headed home – how they formed (usually an underwater earthquake which would cause the ocean floor to shift upwards, displacing water), how in the ocean they just looked like normal waves and how even a mile out from shore they weren’t really a big deal (because wave energy only reaches half the depth of the water, which is why the bottom of the ocean in all those National Geographic films is so still) and how it wasn’t until they reached shore that they became a problem (because the depth of the water is suddenly much shallower, driving the wave up and giving it a more powerful velocity).  Then the real tsunami happened and, while it was a true tragedy and I donated money to the cause, suddenly it wasn’t as fun to talk about theoretical tsunamis while intoxicated anymore because 1) everyone knew how they formed and 2) it wasn’t really funny.

The truth is, I’m so fascinated by tsunamis because they really, really scare me.  But I rested easy because, due to the tectonic activity – or lack thereof – on the Atlantic Plate (which pulls apart rather than smashes together, as the Pacific plate does), the east coast would never see a tsunami.  Right?

Wrong.

As it turns out, the east coast is likely to be in for the biggest tsunami of them all, aptly named the mega-tsunami.  This is a tsunami caused not by tectonics, but by an incredible amout of water displacement due to a huge landslide. 

The mega-tsunami phenomenon was first observed in Alaska.  Scientists who visited the area in 1953 had concluded that damage to the tree lines indicated huge waves had devastated the area in the past, but they had no idea what could have caused them.  In 1958, a moderate landslide in that same area, which created a wave taller than any sky scraper on Earth, gave them their answer.  They realized that a huge landslide would create a massive tidal wave, one even larger than what had happened in Alaska.  This kind of tsunami could occur in Africa and obliterate many of the large port cities on the East Coast with the force of a jetliner.  A true mega-tsunami.

Mega-tsunamis are very rare, occuring just once every few thousand years, and are usually caused by the collapse of volcanic islands into the sea.  The last mega-tsunami occured 4,000 years ago.  Can you do the math? We’re due for another, and conditions are ripe. 

The biggest threat comes from La Palma in the Canary Islands.  According to an article by the BBC online,

In 1949 the southern volcano on the island erupted. During the eruption an enormous crack appeared across one side of the volcano, as the western half slipped a few metres towards the Atlantic before stopping in its tracks. Although the volcano presents no danger while it is quiescent, scientists believe the western flank will give way completely during some future eruption on the summit of the volcano. In other words, any time in the next few thousand years a huge section of southern La Palma, weighing 500 thousand million tonnes, will fall into the Atlantic ocean.

What will happen when the volcano on La Palma collapses? Scientists predict that it will generate a wave that will be almost inconceivably destructive, far bigger than anything ever witnessed in modern times. It will surge across the entire Atlantic in a matter of hours, engulfing the whole US east coast, sweeping away everything in its path up to 20km inland. Boston would be hit first, followed by New York, then all the way down the coast to Miami and the Caribbean.

The unique composition of the volcano – water that was captured in fissures can’t escape, boils and creates steam – increases its instability.  I saw a really fascinating/nightmare-inducing program about mega-tsunamis on the Discovery Channel which explained the devastating impact this particular one could have on the East Coast.

Read more about the causes of all kinds of tsunamis and some lovely tidbits on mega-tsunamis here.

I would say I’m moving to Kansas, but even they have tornados.  I guess you’re not safe anywhere…

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