Tsunami that devastated the ancient world could return

AFP on Yahoo ^ | 3/9/08 | AFP

[NormsRevenge]

PARIS (AFP) - "The sea was driven back, and its waters flowed away to such an extent that the deep sea bed was laid bare and many kinds of sea creatures could be seen," wrote Roman historian Ammianus Marcellus, awed at a tsunami that struck the then-thriving port of Alexandria in 365 AD.

"Huge masses of water flowed back when least expected, and now overwhelmed and killed many thousands of people... Some great ships were hurled by the fury of the waves onto the rooftops, and others were thrown up to two miles (three kilometres) from the shore."

Ancient documents show the great waves of July 21, 365 AD claimed lives from Greece, Sicily and Alexandria in Egypt to modern-day Dubrovnik in the Adriatic.

Swamped by sea water, rich Nile delta farmland was abandoned and hilltop towns became ghost-like, inhabited only by hermits.

The tsunami was generated by a massive quake that occurred under the western tip of the Greek island of Crete, experts believe.

Until now, the main thinking has been that this quake -- as in the Indian Ocean tsunami of December 26, 2004 -- occurred in a so-called subduction zone.

A subduction zone is where two of the Earth's plates meet. One plate rides over another plate which is gliding downward at an angle into the planet's mantle.

Subduction zones usually have measurable creep, of say a few centimetres (inches) a year. But as the rock becomes brittle and deformed at greater depths, these zones can also deliver titanic quakes, displacing so much land that, when the slippage occurs on the ocean floor, a killer wave is generated.

The 365 AD quake occurred at a point on the 500-kilometre (300-mile) -long Hellenic subduction zone, which snakes along the Mediterranean floor in a semi-circle from southwestern Turkey to western Greece.

Researchers in Britain have taken a fresh look at this event and have come up with some worrying news.

University of Cambridge professor Beth Shaw carried out a computer simulation of the quake, based especially on fieldwork in Crete where the push forced up land by as much as 10 metres (32.5 feet).

They estimate the quake to have been 8.3-8.5 magnitude and that its land displacement -- of 20 metres (65 feet) on average -- puts it in the same category as the 9.3 temblor that occurred off Sumatra in 2004.

They conclude the slippage occurred along 100 kilometres (about 60 miles) on a previously unidentified fault that lies close to the surface, just above the subduction zone.

The quake happened at a depth of around 45 kilometres (30 miles) -- around 30 kilometres (20 miles) closer to the surface than would have been likely if the slip had occurred on the subduction fault itself.

After the 365 AD quake, the fault is likely to remain quiet for around 5,000 years.

But if the tectonic structure along the rest of the Hellenic subduction zone is similar, a tsunami-generating quake could strike the eastern Mediterranean in roughly 800 years, the scientists estimate.

The last tsunami to hit the eastern Mediterranean occurred on August 8, 1303. According to research published in 2006, a quake off Crete of about 7.8 magnitude hit Alexandria 40 minutes later with a wave nine metres (29.25 feet) high.

"That there has been only one other such event... in the past 1,650 years should focus our attention on the modern-day tsunami hazard in the eastern Mediterranean," the new study, published in the journal Nature Geoscience, warns.

"Repetition of such an event would have catastrophic consequences for today's densely-populated Mediterranean coastal regions."

The UN Educational, Scientific and Cultural Organisation (UNESCO) is setting up a tsunami alert system for the Mediterranean as part of a global network established after the 2004 Indian Ocean disaster.

[Strategerist]

An active Volcano called Cumbre Veija erupted in 1949 causing a partial collapse of a major portion of the island's western flank. Another eruption occurred in 1971. An eruption some time in the future will cause a total collapse sending a wave 300 feet high across the Atlantic at a speed of approximately 500mph. It will strike the entire eastern seaboard. The wave height, by some estimations, will be 165 feet by the time it reaches the east coast and move upto 12 miles inland.

This has been debunked by a consensus of tsunami scientists. Media didn't bother to tell you that, because it isn't exciting. Any collapse of La Palma would create only a local tsunami. Collapse tsunamis actually don't propagate long distances nearly as well as earthquake tsunamis, though they can be very high locally.

[streetpreacher]

If not, it would seem like a good terrorist target. Detonate enough explosives to send La Palma into the ocean. Stuff for movies.

[Archangel86]

... And that’s why I live in Minnesota.

[jerod]

Hey... We just had a tsunami a couple of years ago that took the lives of 250,000+ people. How often is an event like that going to happen in the course of 10 life times?

The answer is - Not a whole heck of a lot.

Relax! If you’re scared of the sea move away from it.

[SunkenCiv]

Thanks for the pings Perdogg and The Spirit Of Allegiance.

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[SunkenCiv]

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	Gods Graves Glyphs	Thanks for the pings Perdogg and The Spirit Of Allegiance. To all -- please ping me to other topics which are appropriate for the GGG list. GGG managers are Blam, StayAt HomeMother, and Ernest_at_the_Beach
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[B-Chan]

Source

[budwiesest]

With an area covering four-fifths the surface of the earth, we should respect what power it may possess.

[Berosus]

In 2006 I moved to Kentucky, after forty years in Florida. So far it hasn’t been a mistake.

[bmwcyle]

A toon could drop an anvil on our heads also.

[Grimmy]

All the Great Tsunami prophets are going to feel so silly when it’s Sky Fall that gets em.

[Caramelgal]

This has been debunked by a consensus of tsunami scientists. …collapse of La Palma

I watched a program about La Palma and wondered if its collapse could really generate 165 foot wall of water to hit the East Coast.

When you think about it, dropping a large heavy object into water will generate a wave but its effect is local and it dissipates rather quickly given a large enough body of water.

So if I do a cannon ball into the middle of a small pool, the wave created will hit all sides of the pool. But if I cannon ball into a larger and deeper body of water like a lake, it won’t even cause a noticeable ripple on the opposite shore.

Of course a mountain falling into the ocean will displace a lot of water and make a darn big splash and cause massive damage to any nearby islands and local shipping, but I’m a little skeptical that NYC would be inundated by a 165’ wall of water.

http://www.lapalma-tsunami.com/

[Man50D]

This has been debunked by a consensus of tsunami scientists.

Who are these so called consensus of scientists?

Media didn't bother to tell you that, because it isn't exciting.

And neither did you. You're vague and general statement lacks any credibility without citing the very sources you claim dispute a landslide generated tsunami.

[ThanhPhero]

Tsunami warning in the Mediterranean wouldn’t be worth much. Distances are too short.

[Man50D]

When you think about it, dropping a large heavy object into water will generate a wave but its effect is local and it dissipates rather quickly given a large enough body of water.

It seems to me you are comparing apples to oranges. Your body is not generating a wave extending down to the ocean floor. It is only creating a surface wave. The debris from a massive landslide will reach the ocean floor and therefore generate a tsunami that extends down to the ocean floor as does an earthquake generated tsunami. Some energy will be lost reducing the initial height from 300 feet down to 165 feet but there isn't enough friction between La Palma and the U.S. to dissipate the tsunami.

Of course a mountain falling into the ocean will displace a lot of water and make a darn big splash and cause massive damage to any nearby islands and local shipping, but I’m a little skeptical that NYC would be inundated by a 165’ wall of water.

There is one factor you're not considering with respect to NYC. Long Island Sound narrows as you move towards NYC. The narrowing of Long Island Sound along with the rising ocean floor may very well push the wave height of a tsunami to at least 165 feet and possibly higher.

[Dustbunny]

Interesting.

Mother earth just doing her thing.

[ASA Vet]

Check this out

[cake_crumb]

"Repetition of such an event would have catastrophic consequences for today's densely-populated Mediterranean coastal regions."

Oh, the asteroid will hit us and destroy all life on Earth before that ever happens...

[cake_crumb]

"(I wonder where it has been hiding all this time.)"

Maybe the Bush administration borrowed Wesley Clark's time machine to go back and suck it up into Rove's weather machine so they can unleash it on the masses...to profit Halliburton, of course.

[Larry Lucido]

Yes, but nobody in 364 AD got hit by a bus, so it’s not significant.