The Mega-Tsunami

[Semjax]

So I was watching the youtube Discovery Channel Segment on the 'Mega-Tsunami' which scientists have predicted would travel over the entire Atlantic to devastate at least 12 miles inland of the entire eastern coast from New York to Miami. I'm not skeptical of this, not by a long shot especially considering that it has happened before and will happen again most likely, but the skepticism lies with my friends who believe that the attempt to say that a wave would travel over the entire Atlantic ocean is nearly impossible, and beyond that would kill basically all life on the planet due to the massive shift in the Eco System due to its major shift of water. So I was wondering what everyone else's opinion of it is, since I can't successfully talk about it with my friends because most don't care, and the one that does care brings religion into it.

[Ophiolite]

I would probably ask your friends what is it that makes them believe their education better equips them to predict the beahviour of waves generated in the ocean by massive landslides than physicists, mathematicians and geologists, who have spent years studying the relevant background. Incredulity is not an argument against anything. For example, I can't believe anyone is as stupid as your friends, but my incredulity does not prevent their stupidity.

 

More to the point, show them a print out of this research paperon the subject and ask them which part of the maths in section 3 they disagree with.

 

Next explain to them that this is only a major shift in water from a human standpoint. It's basically the top of 3m of an ocean that is kilometres deep and is only one of the oceans on the planet. It would devastate the eastern seaboard, but the global impact would be barely detectable a millenia or two hence.

 

I'm not sure what you can do with the religious guy. How does he bring religion in? God's punishment for the sins of New Yorkers?

[CaptainPanic]

For those who don't have a lot of time to spend on Youtube, could you please summarize what (according to the documentary) would cause the Mega Tsunami?

Generally speaking, the one-hour documentaries of Discovery can easily be summarized into a couple of sentences. For the rest it's just repetition, silly special effects and unnecessary interviews... and some more repetition.

 

According to this Discovery documentary (also youtube, I only checked part 1/5), a normal earthquake will just cause a wave of about 10 meters, along perhaps hundreds of kilometers. But that's a normal tsunami. What makes a Mega Tsunami so Mega?

[Ophiolite]

I haven't watched the youtube video, but the event they are probably talking about is a collapse of part of the Cumbre Vieja volcano on La Palma in the Canary Islands. Such collapses are known from subsea landslide material. In the research paper by Ward and Day I linked to in my earlier post they explore the effects of a catstrophic collapse of 500 cubic kilometres of material into the ocean. They then compute the probable wave height and subsequent dispersion within the Atlantic. This, according to their calculations, still produces a sufficient wave height at the US Atlantic seaboard to produce extensive run up and major damage and probable loss of life. Since it would effect the entire seaboard emergency services could not readily be sourced from adjacent communities. This would be a disaster on an unparalled scale for any western country.

 

The analysis conducted by Ward and Day followed hypothesised flank failure noted by Day (DAY,S et al.(1999),Recent structural evolution of the Cumbre Vieja Volcano, La Palma, Canary Islands: Volcanic rift zone reconfigurtion as a precursor to volcanic flank instability? J.Volcanol.Geotherm.Res., Special Issue 94 (1–4), 135–167. ) and Carracedo (CARRACEDO,J.C., et al.(1999),Giant quaternary landslides in the evolution of La Palma and El Hierro, Canary Islands, J.Volcanol.Geoth.Res.94 (1–4), 169–190.) Evidence supporting the potential for flank failure is uncertain. A detailed gravimetric and GPS study conducted in 2006/2007 that also included earlier measurements was inconclusive.

 

Further analyses by other researchers claimed Ward and Day's findings were exagerated. However, Lovholt in "Oceanic propagation of a potential tsunami from the La Palma Island", using a more sophisticated model produced results that, though not as severe as Ward and Day, are still extremely serious. It is notable that they see the worst situation being in north west South America, rather than the Atlantic seaboard of the US and Canada.

[Realitycheck]

This documentary I saw about abnormal freak rogue waves seemed to touch base on the timing of different wave influences congregating to produce very rare waves that were like 3 to 5 times higher than normal high storm waves. They even reproduced the effect in little 1" thick glass wave effect replicators. It seemed very odd but, in effect, well thought out and demonstrated. It was really weird watching columns of water this tall and this steep moving across the water.

 

I guess thats not the same as tsunami, but I thought I would point it out. Sorry to change the subject.

Edited August 1, 2011 by Realitycheck

[Ophiolite]

Damn! Unable to edit my post. It should have read "North east south America" not "North west".

[CaptainPanic]

Further analyses by other researchers claimed Ward and Day's findings were exagerated. However, Lovholt in "Oceanic propagation of a potential tsunami from the La Palma Island", using a more sophisticated model produced results that, though not as severe as Ward and Day, are still extremely serious. It is notable that they see the worst situation being in north west north east South America, rather than the Atlantic seaboard of the US and Canada.

I guess in this case it matters where the landslide occurs, and in which direction the landslide moves.

With a "normal" earthquake when the entire seabed moves up or down, the wave travels in all directions.

 

Such a wave (caused by a 500 cubic kilometer landslide) would definitely reach the cost on the other side of the ocean, and cause devastation.

[Ophiolite]

They have a reasonable idea of the direction of travel of the failing slab, since there is an extensive fault along which the rupture is predicted to take place.

I've been trawling through a a dozen or more research papers on the topic and it is clear that Ward and Day's hypothesis is viewed as extreme by other researchers. First there are doubts that the mass of the landslide would be as great as postulated. Some authors suggest 100 cubic kilometres rather than 500. Secondly it seems that slip might occur in stages. Thirdly, more sophisticated modelling indicates that short waves would be generated. These would not be as effective at transoceanic crossing as the longer waves modelled by Ward and Day. There is no doubt that if and when a collapse occurs there will be a tsunami generated and it will cause damage and probably loss of life, it just is unlikely to be as severe as the scenario they postulated.

[JohnB]

Could I just add that mega-tsunamis are also caused by oceanic meteorite impacts.

 

Mega-tsunamis typically leave deposits known as "Chevrons" in their wake and such deposits are far more common that I like. The ad hoc group "Holocene Impact Working Group" is looking at this matter. After reading some of the papers, it's scary. We're talking waves hundreds of metres high and travelling tens of kilometres inland.

[MediaX]

A T-sunami's gains energy as distance is covered over the ocean. The T-sunami (not Predicted) to cover the atlantic and hit America would be far more disastrous than the forum as mentioned. The canary islands, 90 miles from the African coast, there are 7 have a smaller island called Teneriffe. The mountains of teneriffe has a main larger mountain called mount teide that has a fault on the coast that faces America, This fault is visible and can be walked through on foot. The trench about 8 feet wide and 6 feet deep strenches for some distance and threatens to break from the coast of Teneriffe and hit the base of the mountain direct into the Atlantic ocean. The impact into the ocean would create a wave that some documentaries explain could create a wave 100 feet high and the energy as mentioned would contribute to a disaster. A movie was broabcasted in the cinima some time ago that showed the results of a huge wave that covered New York.

 

2012 predictions are quite a worry when we witness the news of recent times.

[Ophiolite]

A T-sunami's gains energy as distance is covered over the ocean.

This appears to be incorrect. What do you think imparts the additional energy to the tsunami?

 

 

ThThe impact into the ocean would create a wave that some documentaries explain could create a wave 100 feet high

How high would the wave be once it had dissipated across an entire ocean? Although 100' high, what would the wavelength be?

 

A movie was broabcasted in the cinima some time ago that showed the results of a huge wave that covered New York.

 

You do realise that movies are even less reliable than chicken entrails when it comes to scientific accuracy?

 

2012 predictions are quite a worry when we witness the news of recent times.

They are only a worry if you are unable to assess news and predictions in calm,objective, rational, scientific manner. Consider that: if you are worried by the predictions then you are not being calm, objective, rational, or scientific.

[Phi for All]

...the skepticism lies with my friends who believe that the attempt to say that a wave would travel over the entire Atlantic ocean is nearly impossible, and beyond that would kill basically all life on the planet due to the massive shift in the Eco System due to its major shift of water.

Do your friends understand that a wave, any wave, doesn't really carry much water with it? A tsunami that started off the coast of Africa would not be carrying any water from Africa by the time it reached North America. It wouldn't shift a massive amount of water from there to here. The force propagates from water molecule to water molecule and it's the force that travels, not the water itself.

 

When the force reaches land, the friction with the sea bed will raise the height of the wave and cause it to crest. That is where the extra water that pushes inland comes from.

[John L]

Tsunamis are just another reason why I tend to stay away from the beach. I spent four years in Charleston, at the Citadel, and when I graduated, I had had enough salt, sand, and stench, to last me a lifetime. I'm a mountains sort of person now, and a long time resident of East Tennessee.

 

But I have been following this topic for a few years now, and agree that while the prospect of the side of an island falling suddenly into the ocean is very small, it does happen. Just one detailed look at the Hawaiian Islands and the small size of the older islands, along with the undersea floor 'runout' patterns leading away from them, is enough to give one pause. Not to mention the huge fissure running the length of a side of the Big Island, which is slowly trying to allow gravity to do its thing.

 

And certainly the threat of Impactors are Real. With well over two thirds of the planet's surface covered in oceans, it is logical to expect an Impactor to generate terrible devastation along the shorelines.

 

I'll take the mountains any time, where the best gift is clean, fresh, aire.