Talk:Megatsunami

From Wikipedia, the free encyclopedia

This article is within the scope of WikiProject Disaster management, a collaborative effort to improve the coverage of Disaster management articles on Wikipedia. If you would like to participate, please visit the project page, where you can join the project and see a list of open tasks.
??? This article has not yet received a rating on the quality scale.
??? This article has not yet received a rating on the importance scale.
Earth sciences Portal
Megatsunami is part of WikiProject Geology, an attempt at creating a standardized, informative, comprehensive and easy-to-use geology resource. If you would like to participate, you can choose to edit this article, or visit the project page for more information.
B This article has been rated as B-class on the quality scale.
Mid This article has been rated as mid-importance on the importance scale.

The person who changes information on this page take note: 1. The international system of mass is the METRIC system not pounds or tons, the International unit of measurement is the METRE - NOT Meter which is an instrument used to measure such as electric meter, gas meter. However, the world recognises that the people of the north American continent called "Americans" have developed their own corruption of English as used by the rest of the world. The English word Epicentre is recognised internationally as indicating the point on the surface where an eartquake occurs and is immediately above the "Focus." So whilst you may not understand that 1 x 10^3 kg is 1 tonne - it is the Internationally recognised and scientific method of writing it. Science globally uses the kilogram, metre. The USA Scientific community now also use the same system so get with it and stop using "Yanklish" and use International English. Also leave the editing of this page to the scientists who are monitoring it otherwise you may well find it locked to stop further vandalism by - well we know who.The Geologist (talk) 18:10, 28 March 2008 (UTC)

A section of the article was altered to state that a megatsunami from the island of Las Palmas 'would' destroy U.S. east coast cities and gave specific dates as estimations; this was deleted for lack of credible source information and as it appeared to likely be an attempt at sensation rather than fact.


This article needs some work, as it's remarkably vague (Who were the two geologists? When did they "observe evidence of unusually large waves"? Where is the "nearby bay"? Nearby in relation to what? Is it Lituya Bay?) and possibly states facts incorrectly. Unfortunately, I need to do some research before I touch the article further. --Goblin 01:17, Jul 6, 2004 (UTC)

Also, if I'm reading this correctly, one paragraph says that the last megatsunami happened 4,000 years ago, and the next paragraph says that there was one in 1958. Either this is inconsistent, or stated confusingly enough as to sound inconsistent to me.

Contents

[edit] Article OK

Not confusing to me. the article was referring to the last time a megatsunami was s big it took out the coasts of an entire continent. "Some are so large that they can devastate the coasts of entire continents. The last such event (that we know of) occurred approximately 4,000 years ago".

Good article.

Claudius

Good article, however, I noticed a claim that the Santorini megatsunami was linked to the Exodus. I signed up to strike this out as there is no evidence at all that the two events were contemporaneous, that an event in the Mediterranean would have had an effect on the Red Sea, or that the Exodus even occurred (although this last point is perhaps less important in terms of this article). This was my first try at editing on Wikipedia, so if I'm going about this the wrong way, I'd be happy to hear from other users.

Rob Gentles —Preceding unsigned comment added by Robgentles (talk • contribs) 18:08, 3 March 2008 (UTC)


As the person who put the item about Santorini and the Exodus on the page, I would point you to the academic (Dr Iain Stewart at the University of Plymouth e-mail: science@plymouth.ac.uk and mark it for his attention) who actually has done the research and data to support the claim. Santorini exploded with a VEI 7.5 and is dated at about 3615 BP. The Exodus is documented not only in the Bible, but also in Egyptian and Israeli documents that agree about details. Several academics from various disciplines have agreed that the timing of the Exodus coincided with the Santorini eruption. Archaeological data supporting the crossing of the Red Sea is not robust, but and this is crucial in that some sources claim that the word "Red" as used in modern times actually is a corruption of "Reed." Hence the Israelites crossed the "Reed Sea" and surprisingly such a sea is documented in the contemporary documents and existed in the southeastern corner of the Mediterranean Sea at the time of the construction of the Suez Canal. With this in mind and if you disagree then be polite enough in the first instance to contact me with the evidence supporting your claim. Otherwise leave my postings alone as I happen to be exactly what my name is - a geologist and a volcanologist, and I research my postings BEFORE I post the information. The Geologist (talk) 19:48, 3 March 2008 (UTC)The Geologist.

[edit] Terrorist Threat of Trigging MegaTsunami

I posted comments regarding the possibility of terorists triggering megatsunami events at locations such as La Palma. They were promptly deleted within minutes. I believe the comments are relevant to the page on megatsunami's and on the La Palma page as well. What does it take to have this concern added to the page such that people won't arbritirally delete it? The comments are not meant to be a discussion but to be ask the serious questions about this very real concern. Anyone reading the megatsunami or La Palma pages NEEDS to be aware of this potential threat that they pose and with all the publicity caused by the very sad 2004 tsunami in Asia it's an important opportunity to get the message out to people, who hopfully will ask their government representatives about it. What would an appropriate paragraph about this be? Also were can I find my deleted comments? - peter

I propose the following be added to the megatsunami page or to another page about this important topic:

Megatsunami Terroist Threat It is possible that terroists could trigger a megatsunami event, at locatations such as La Palma, and cause wide spread global destruction. This is a serious threat that needs to be addressed by all governments and concerned citizens. What can you do to ensure that your government is taking actions to prevent such actions and protect these sensitve geological locations?

The above comments aren't written in an encyclopedic style. The Encyclopedia Brittanica for instance, would never say "What can you do to..." Remember that Wikipedia is an encyclopedia.
I suggest you'd be better off writing to your Congressperson or to the Department of Homeland Security if you think it's warranted. -- Curps 09:26, 29 Dec 2004 (UTC)

Thank you for your comments. How about we work to rewrite this topic into encyclopedia style? Any suggestions? There must be a way to include comments designed to have people act on important events even in encyclopedia style? The point isn't that I write to my government representative, the point is to raise the importance of this issue in the entry such that people clearly understand that it's a serious concern. Surely that can be written in an encyclopedic style? The point is to inform the many people reading the page about the nature of the danger. They are the ones who can choose to act or not. Leverage of people power for the betterment of mankind and the planet is what Wikipedia is about, is it not? -- peter

At the end of the paragraph that says:
The aftermath would hold obvious implications for affected populations, governments, and for the global economy. While potentially not as devastating as a supervolcano, a megatsunami would be an unprecedented disaster in whatever region of the world it occurred.
you could add something like "Some even suggest the possibility of this scenario being triggered deliberately by terrorism."


However, I personally don't think terrorism is that much of a threat. A big explosion would produce many small chunks hitting the ocean, and not one big chunk. The multiple small chunks wouldn't trigger a megatsunami. Getting a single big chunk to slide into the ocean would probably be a matter of chance and luck, something Mother Nature might do once in a very long time, but not the typical landslide. -- Curps 09:35, 29 Dec 2004 (UTC)


== NO TERRORIST THREAT LIKELY == Some of you seem to be under the impression that a terrorist attack could cause a mega-tsunami. There is compelling scientific evidence that such a threat is more imaginative than factual. The much hyped future failure of the Cumbre Vieja is also cited as a likely location. Again it is very imaginative but whilst a terrorist attack using the Cumbre Vieja could not be ruled out, any attack would hit several problems before it could even be initiated. Without going into details let me point you in the direction and see if you can argue against this.

How do you bury a nuclear device deep enough? How do you prevent detection of your work?

One non-scientific "cause" of the 26th December 2004 seismic event off the coast of Sumatra was claimed to be collusion between the USA and India to drill a borehole at night deep enough to then lower a nuclear device down and then set the timer so it went off at the time it did? It "MUST BE TRUE" because the USA Never denied it! It "MUST BE TRUE" because the Indian Government Never denied it! This ignored two provable facts - the focus or hypocentre was about 18 km below sea level, and the deepest borehole ever drilled is in Russia on the Kola Peninsula - it's depth? 11 km! Readings etc; from that borehole indicate that the borehole is about as deep as we can currently drill with our current technology. The claim about the Sumatra earthquake also ignored the fact that to drill a hole in the location you need a ship such as those used on the ODP's. Such a vessel cannot turn up at dusk and dissappear at dawn - there isn't enough time to draw the drill string up or put it down the hole. Also the seismic wave generated by a nuclear device is very characteristic - it is a compression wave and is omnidirectional. Still think you could bury a nuclear device on the Cumbre Vieja and cause it to fail?

With respect to the Cumbre Vieja the last eruption occurred in 1971 at the Teneguia vent which is located at the southern end of the Cumbre Vieja. There is no record of any movement indicative of failure with that eruption. The 1949 eruption is considered to have triggered an earthquake with an epicentre near Jedy on the western flank of the Cumbre Vieja. This earthquake is quoted by Ward and Day etc., as the precursor of an imminent failure of the Cumbre Vieja's western flank.

Failure of the flank may occur - but it will take many more eruptions before the whole flank is unstable to fail catastrophically en-masse. Consider this: The Cumbre Vieja stretches in a north-south direction from the Cumbre Nueva to the southern tip of the island - it is traceable underwater and is believed to have erupted within the 20th Century, though the evidence is debated. However, the sub-aerial or exposed length of the Cumbre Vieja is about 25 km long. The length of the rift that opened in 1949 is about 2.5 km long or about 1/10th of the length. The Cumbre Vieja contains several trillion tonnes of rock - so if you are any good at mathematics try working out how much force would need to be released to make it fail en-masse. There simply is not enough nuclear devices in the world!

I trust that this answers several questions, but if not, well I am a volcanologist and one volcano I am working on is the Cumbre Vieja. Believe me there is NO EVIDENCE that it has moved since 1949. I have the data of the 1949 report and current observations using various methods of measurement. The Geologist (talk) 20:40, 5 March 2008 (UTC)

Your suggestion is a good way to include a taste of the terrorist threat discussion. If you saw the BBC documentary "Mega-tsunami: Wave of Destruction" (http://www.bbc.co.uk/science/horizon/2000/mega_tsunami.shtml) about La Palma and how unstable the rock there really is you'd understand that it's a real possibility for expert explosives experts to trigger. I'm not the one making up this threat. Here is a link http://www.benfieldhrc.org/SiteRoot/in_the_news/press_cuttings/Insurance%20Day/new_york_tsunami.htm to an article about it and a quote: "Scientists at the Benfield Hazard Research Centre believe the catastrophe will be triggered by volcanic activity in the Canary Islands (La Palma)." -- PeterWLount

Well, if you like, go ahead and add that sentence that I suggested. -- Curps 09:53, 29 Dec 2004 (UTC)
thanks for your suggested sentence. I've added it in and it's a good start. What about linking to the BBC documentary page that I reference in my above comment? PeterWLount
I think someone already added it earlier, under the "External links" section. -- Curps 10:02, 29 Dec 2004 (UTC)


Yes, that is the same link. I do think that the issue needs to be highlighted stronger. As we can see from recent events in Asia and NYC the treat needs to be taken seriously. Peterwlount 10:09, 29 Dec 2004 (UTC)
Yes. The natural threat is serious enough, even without a possible terrorist threat. But for various reasons, I think terrorists would have a difficult time to pull it off... too much conventional explosive would be required and it would have to be detonated deep underground instead of at the surface. But at least Homeland Security should take the natural threat seriously. -- Curps 10:16, 29 Dec 2004 (UTC)


The point is that it's likey much easier for terroists to cause a La Palma megatsunami event than to obtain and explode a nuclear bomb in North America. Also La Palma would likely cause more devestation than a single nuke. Discounting the possibility without a proper scientific analysis isn't advisable. The reason that La Palma is a problem is it's specific brittle rock formations that are fragile and sensitive to disturbance. It could take a lot less less well placed (pun intended) explosives than one would think to let loose these rock formations. The documentary is a must see. Peterwlount 10:22, 29 Dec 2004 (UTC)
I think one of the articles linked to at Cumbre Vieja (the third BBC article) mentions that the megatsunami only happens if a single entire block of rock slides into the ocean in one piece. If it's broken up into ten smaller pieces, there won't be a megatsunami. That's why even if the terrorists were able to cause a massive explosion, it would probably be beyond them to cause one single block of rock to slide into the ocean rather than a million smaller boulders.
Anyways, I'm going to call it a night. Good talking to you. -- Curps 10:26, 29 Dec 2004 (UTC)
Yes, and to you a peacefull and prosperous new year.Peterwlount 10:27, 29 Dec 2004 (UTC)
Someone keeps removing the addition without any explaination. Sigh. Peterwlount 01:32, 30 Dec 2004 (UTC)
I deleted it because it is really silly. The amount of energy required is of the order of a volcanic eruption or large earthquake, which is in the range of large nuclear weapons and impossible to achieve with conventional explosives. Such a nuclear explosion would have to be set off deep underground under the ocean and this major engineering feat would have to be accomplished without detection. We are all entitled to our paranoid fantasies but this one goes too far and spoils an otherwise good article. --Zero 10:57, 30 Dec 2004 (UTC)
Very silly indeed. The much smaller landslide caused by the 1980 eruption of Mount St. Helens (still the largest in recorded history) was set off by an eruption that released an amount energy equal to 20,000 Hiroshima-sized atomic bombs. If a terrorist had that many atomic bombs, I'm certain they would find other uses for them other than creating the possibility of causing a tsunami-inducing landslide. However, human activity can influence volcanic activity. So it is theoretically possible that something less - perhaps much less - than 20,000 atomic weapons could cause the collapse if the volcano is close to erupting anyway. One could then, and only then, be able to push things in a desired direction with relatively a small amount of force. --mav 05:52, 31 Dec 2004 (UTC)
Just because you think it's "silly" doesn't negate the possibility. Mount St Hellens wasn't as unstable as La Palma. Let me reiterate the following: If you see the BBC documentary "Mega-tsunami: Wave of Destruction" (http://www.bbc.co.uk/science/horizon/2000/mega_tsunami.shtml) about La Palma and how unstable the rock there really is you'd understand that it's a real possibility for expert explosives experts to trigger. I'm not the one making up this threat. It's not a stretch to imagine humans studying this highly unstable geology in detail and using specific controlled demolishion of high explosives, just like taking down a sports statium, to bust open the "natural dams" holding up the massive quantities of water inside La Palma. It's the water inside La Palma that's the threat since it's the sustpected cause of the 16 meter slip of a 2km section of the mountain side that occured the last time the island erupted. In addition, the point about responsible warnings is that they are to get people thinking about the possible reality of something. If you keep deleting a warning you are supressing an appropriate and important form of communication and preventing people from having the chance to think about the threat. Most likely due to the repeated deletions a new page is needed to counter your inappropriate deletions. If you have an alternative version to introduce please do so. I'm not interested in an add/delete war, I'm interested in an appropriate article to document the potential of this weapon embodied in La Palma and other unstable megatsunami locations. -- PeterWLount


Comment re the above:

[edit] Headline text

Where did you get the 16 metre slip you quote from? If you read the original description (en Espanol, senor) written by Rubio Bonelli the data he quotes is as follows: Width of opening ~1m, vertical displacement varies between 1 and 2 metres and the length of the rift that was active is approximately 2.5 km. There is insufficient energy stored in ALL the worlds nuclear arsenals to displace the entire 25 km length of the Cumbre Vieja into the ocean. So whilst certain terrorists might cause you to have nightmares, rest assured that currently there is no way they could plant sufficient explosives - conventional or nuclear on the Cumbre Vieja to cause it to fail catastrophically. Whilst the flank may fail it is more likely to be small sector collapses rather than catastrophic failure en-masse. Therefore most geologists and volcanologists - which is what I actually am, are of the opinion that the risk of a very large tsunami generated by the Cumbre Vieja undergoing catastrophic failure en-masse is rather low, much over hyped by certain people including the media. It sells news papers and draws big viewing figures. My own ongoing research on La Palma shows that the Cumbre Vieja is currently stationary and has remained so since 1949 as the dimensions recorded since have not altered. The Geologist (talk) 20:29, 5 March 2008 (UTC)

That article you cite says nothing about any terrorist threat. If you want your "theory" to gain traction Wikipedia is not the place since WE ARE NOT A PRIMARY SOURCE. Try to get your idea published in the the scientific literature first and then come back to cite it here. See Wikipedia:What Wikipedia is not #s 8 (Personal essays), 9 (Primary research), 16 (News reports) --mav 17:03, 31 Dec 2004 (UTC)
I've added the following to include the disenting voice of the "deleters": "While some are skeptical of the probability a few suggest the possibility of this scenario being triggered deliberately by terrorism using controlled demolition to affect La Palma's unstable geology." -- PeterWLount
Not good enough. Why not add the possibility of megatsunamis being created by aliens or by malicious demons? That's about as credible. Show us a qualified person (someone with scientific authority to speak about massive earth movements) who thinks this "threat" is credible. Btw, the BBC show does not make any claim about terrorist threats. It is a crackpot idea and no more than that. --Zero 15:38, 31 Dec 2004 (UTC)
I would like to add that it _could_ be triggered by large scale demolition work, but this does not have mean malisicious intent, a goverment may decide to demolish pieces off of it in order to cut down on the mass of land that will utlimately create the tsunami when it plunges into the ocean. But any such operation would not go unnoticed and therefor any terrorist threats are moot --Jimius 15:48, 31 Dec 2004 (UTC)

[edit] Math

The point is that it's likey much easier for terroists to cause a La Palma megatsunami event than to obtain and explode a nuclear bomb in North America.

I don't know about that, I think it would take some math for that, a lot of math to correctly detonate the correct explosives with the right strength at the right times at the right places. And Zero0000 is right as well, the explosives would need to be detonated deep underground, and we're talking about 5.5 trillion tons (I'm not talking about tonnes) of earth that will be causing this megatsunami.

I agree with the anonymous person who wrote the above. It would be very easy to detonate a nuclear explosion in North America. Only 12 kilograms of plutonium is sufficient to cause a self-sustaining fission reaction; that amount could be carried in a briefcase. The same can't be said for La Palma; it would take a lot of work, as well as substantial geological knowledge, large-scale drilling crews and lots of time. It cannot be done. thefamouseccles 13:53, 1 Feb 2005 (UTC)

12 kg? - no the figure is 11 pounds - read the report regarding the Manhattan Project. The Geologist (talk) 20:30, 5 March 2008 (UTC)

[edit] 15-25 meters?

What source said something about 15-25 meters? I found several that said 90 meters (295 ft). --Mac Davis 10:51, 1 Jan 2005 (UTC)

I Found several that said something like 150 to 500 meters.Wiki236

You might like to look at the paper by Ward and Day 2001. Ward, S.N. and Day, S. 2001. Cumbre Vieja Volcano — Potential collapse and tsunami at La Palma, Canary Islands. Online version in Adobe PDF format. The Geologist (talk) 20:31, 5 March 2008 (UTC)

[edit] Why does this article exist?

Nowhere in science is a 'megatsunami' ever referred to. There's certainly no scientific defintion. It's purely a pop-culture term. Dan100 19:57, Jan 4, 2005 (UTC)

I have heavily edited the article to reflect this, and corrected many of the fallacies previously in the article. Dan100 20:12, Jan 4, 2005 (UTC)

While I make no claim that it's the perfect source, it has been used on at least two Discovery Channel documentaries by geologists during interviews, so I think that that justifies the article's existence. You certainly can't call these events normal tsunami. thefamouseccles 13:49, 1 Feb 2005 (UTC)
This article should simply state: Megatsunami is a non-scientific term sometimes used to mean a very large tsunami. or else be removed altogether (linking the search term to tsunami).
Motivation: A tsunami can by definition be caused by any seismic event, including land slides, submarine slides, earthquakes, submarine volcanic eruptions, meteorite impact, and so on. It is completely un-scientific to separate the two. The fact that geologists use the term in a TV program is equivalent to them saying "it was a very very large tsunami", since mega is a prefix used to signify something very large. Well, this is my POV as someone who has worked with classifying natural disasters.--Lindorm 21:05, 19 July 2006 (UTC)


== What is a "Mega-tsunami?" == Several media sources around the world refer to "mega-tsunamis" which the above posts ask about. It is NOT a SCIENTIFIC TERM nor is it used by geologists when discussing tsunamis with each other. It was coined by the BBC - British Broadcasting Corporation for the Horizon programme "Mega Tsunami Wave of Destruction" which was screened by the BBC2 channel and broadcast 12 October 2000. It is of the same non-scientific / geological language that gave us "Super Volcano!" There is no such volcano, but what there is are "Super eruptions." The term is used by the media and geologists to explain the very simple fact that such tsunami or volcanic eruption is beyond our normal understanding and could potentially have serious implications far beyond the local area. As the 26th December 2004 earthquake and resultant tsunami showed, a natural event in one location can cause devastation thousands of kilometres away from the origin. The Geologist (talk) 20:32, 5 March 2008 (UTC)

[edit] NPOV Query

"In modern times, this phenomenon would be made even more likely to occur based upon President George W. Bush's adherence to scripture and disregard of the Kyoto Accords. The sinking of the polar ice caps is likely to follow the abandoment of such environmental accords and create large scale destruction from these giant waves."

This doesn't seem to be a particularly neutral point of view.

--Staz 21:36, 4 Jan 2005 (UTC)

It's also a load of rubbish. Dan100 20:14, Jan 6, 2005 (UTC)

There is a very rude word to describe what you are claiming. The melting Ice Caps will add salt water back into a liquid state. This will not cause a tsunami. The Geologist (talk) 20:32, 5 March 2008 (UTC)

[edit] terrorists

I fully agree with the danger of that terrorists can take advantage of such environmental desasters, what i donot understand is why the collaps of la palma cannot be stopped. I suggest that America should pay every dollar in investigating this problem instead of sending the money to Mars. I'm not a scientist, i think you noticed that,but there seems to be water in the mountain of la palma, that will cause the collapse, maybe they should get this out, again you see i'm not a scientist, but maybe if you put 50 scientists on this problem for 10 years you have a solution and after that we can go to Mars. Why wait for this to happen its stupid. The same with prevention of a hit from a meteor from outer space, because it happens only once in 100.000 years, they put it in nuclear bombs. A meteor is a 1000 nuclear bombs at once!

by dmx from Holland

It takes more than a bit of scaffolding to hold a 5-trillion-ton mountain in place, and any drilling, building or mining that's substantial enough to make a difference might very well be substantial enough to trigger the landslide itself. What we need to do is stop trying to prevent landslides and tsunami and volcanic eruptions, and start understanding what we can do to prevent human death from the effects of these disasters. Early warning systems, for instance. It'd make a lot more economic and environmental sense, plus it's just common sense: to take your meteorite example, how will we stop a chunk of solid rock - sometimes even iron - moving at nearly 40,000 kilometres an hour? And I think that the idea of terrorists causing a landslide like this is just paranoia; I agree with Zero on that. People are too afraid of terrorists; if we fear them, they've already won. thefamouseccles 13:38, 1 Feb 2005 (UTC)

[edit] Prevention possibilities

This is technically original research. If it's feasible, I think it's important enough to put in a place like this (the talk page).

3 potential ideas (though I currently have insufficient understanding of physics to know whether they are feasible).

1) Wrap Volcanic landslide prone areas such as that near the Cumbre Vieja volcano on La Palma in sufficient density of carbon nanofiber composites to prevent collapse. Have sufficient slack in the wrap for minor movement to occur (such as is normal in volcanic expansion of land) without causing the nanofiber wrap to break, but sufficient taughtness that it can prevent a potential tsunami causing collapse. Said wrap can be sub-surface (against the rock), thus allowing normal vegetation and animal life above it.


2) Quarry the gigatons of rock out. Do so in a way that would prevent the quarrying to unintentionally cause the very collapse it is trying to prevent.

2)A) Do number 2 after you have done number 1. This will help prevent potential collapses while quarrying. It's possible other support mechanisms are strong enough to support the teratons of mass (especially as the mass is already partly supported by the island it's a part of.


== WE DO NOT HAVE THE TECHNOLOGY - SIMPLE == Not only do we not hve the technology to prevent several trillion tonnes of rock from catastrophically failing or entering the ocean we do not have the technology to produce the carbon fibre in sufficient quantity or thickness. You might as well ask why didn't they stop the 26th December 2004 earthquake? If we had used all the equipment in the world the earthquake would still have happened the tsunami would still have happened because the technology - carbon fibres nano or otherwise cannot contain the kind of forces that are involved.

We have no more chance of stopping the Cumbre Vieja from failing at some future date than we have of stopping the sun rising tomorrow morning. We are talking of forces beyond anything you can comprehend. The Geologist (talk) 20:33, 5 March 2008 (UTC)


If a tsunami occurs: 3) Vertically or angled deployable/telescoping breakwaters on the continental shelf. These can be deployed if a tsunami early-warning signal goes off. They would cause the low-level tsunami waves to (at least partially) prematurely crest in the ocean by giving them a false rise to crest against. It's possible the breakwaters couldn't fully withstand the sheer power of the tsunami wave front and would consequently be destroyed while only mitigating some of the tsunami's power, but this is probably preferable to having the full impact of the wave hit mainland. If more than one layer of breakwaters exist, this might result in a significant decrease of tsunami force against the mainland (where a mainland can be an island or continent). 24.22.227.53 15:38, 2 September 2005 (UTC)

Wrong - the floor of the ocean isn't smooth. It really is rough down there - natural "breakwaters" and the wave just rides over them. The ONLY way to dissipate the energy present in a tsunami is to let it batter itself to death against cliffs. You can calculate the energy present in a mass and then apply the inverse square root theorem to it to see how much energy is present at one thousand, two thousand kilometres away. The inverse square root theorem states that the power present at a point "O" is halved at a distance equal to 2O and therefore at a point 2000 km away from the source the energy present is half that present at the source, at 4000 km it is 1/4 and remember with a tsunami we are talking of large as in 10 to the 20th or more power of joules. The Geologist (talk) 20:33, 5 March 2008 (UTC)

[edit] La Palma research (grammar)

"the source of the next large-scale megatsunami is the island of La Palma, in the Canary Islands, ~although further research has dismissed the threat. However,~ recent research has found that a large section of the island will break off into the ocean, causing a megatsunami"

I don't know of what research this paragraph refers to, but as it stands the wording is somewhat contradicatory and more than a little ugly. So I'm going to cut out the text denoted by tildes, and hope that someone out there with more knowledge on the topic can clarify or re-write. - Whoops sorry I forgot my signature --Tocqueville 17:08, 30 July 2005 (UTC)

La Palma is a volcanic ocean island and as such its structure is inherently unstable - but then any substance including snow on any slope is inherently unstable. There is evidence that during the 1949 eruption PART OF THE CUMBRE VIEJA - which is approximately 25 km, long ruptured. The length of the 1949 rupture is about 2.5 km or about 1/10th of the length of the Cumbre Vieja. Day et al have hypothesised that a future eruption would cause the catastrophic failure western flank of the Cumbre Vieja and the media picked this up. It has been misrepresented in many ways. One it is very unlikely that the whole 25 km long section would faile en-masse, two; the possibility of sector failure is considerably higher but has not been reported, three; the 1949 rupture moved about 2 m vertically and about 1 m horizontally. These dimensions are recorded in the papers by Rubio Bonelli - see "Further reading" and monitoring of the rupture has not indicated any changes in the dimensions. I am involved in ongoing research and monitoring of the volcano and IF the flank was to become unstable to the point where failure was imminent, there would have been many more eruptions at various locations along the Cumbre Vieja.

Will the whole flank fail? This is considered to be the very worst case scenario and unlikely. Since we have not witnessed edifice failure on a volcanic ocean island we have no way of knowing whether a tsunami will be localised or travel across an ocean. We have no way of knowing if the failure will be slow which will therefore NOT generate a tsunami of transoceanic proportions or sudden and may therefore generate a transoceanic tsunami. The media and certain geologists hyped the situation and panic reigned, pseudo-scientists raised the tempo by claiming that terrorists could plant explosives - nuclear or conventional within the edifice and cause it to fail without considering how they could carry out such an attack.

Consider this - some terrorists decide to attack the USA and cause massive devastation and death. Why go across the ocean to do it? Why not get hold of some plutonium then build your bomb in the subway of a USA city? Then detonate it taking out that city and perhaps others too, It's quicker, no warning and you don't have to carry the plutonium around the world - the Cumbre Vieja failing en-masse will trigger a tsunami warning and evacuation of much of the eastern seaboard of the USA. Because there will be time to do something. You don't attack your perceived enemy from another continent you do so in places that will cause the maximum devastation within the country.

Or what about the flank of Kilauea - it is unstable slid about 4 m in 2005 and generated a tsunami that was localised. So La Palma isn't the only volcanic ocean island that "threatens" the USA, it just received a lot of publicity. The Geologist (talk) 16:03, 9 March 2008 (UTC)

[edit] Definition

The first paragraph contains two comments regarding the definition of a megatsunami, which seem to contradict each other.

  1. "A megatsunami is a form of displacement wave, related to tsunamis in name only."
  2. "the term generally refers to tsunamis with waves from 40 metres (131 feet) to over 100 metres (328 feet) tall."

The first seems to indicate that a megatsunami is not a type of tsunami, the second indicates that a megatsunami is a type tsunami. Can anybody clarify this, please? Cheers TigerShark 15:41, 4 September 2005 (UTC)

Whups, true !! Will do ! FT2 08:25, September 8, 2005 (UTC)

A so called "mega-tsunami" is just a BIG tsunami and the term was coined by the BBC and is used by the media not geologists - I am a professional geologist and volcanologist. The Geologist (talk) 20:39, 5 March 2008 (UTC)

[edit] Megatsunami vs tsunami

I'm quite confused as to the difference between a megatsunami and tsunami. The article doesn't explain it very well. AFAIK, a tsunami can be caused by any number of things, meteors, landslips, seismic activity, volcanos etc. This article appear to suggest megatsunamis are caused by landslip and meteors whereas tsunamis are caused by seismic activities which I'm pretty sure isn't true. Seismic activity is AFAIK the most common cause for tsunamics, probably because it's rare for landslips not caused by seismic activity to be of sufficient size and power to cause a tsunami of any significance and meteors are very uncommon. Of course they do occur, the Vajont Dam disaster was a tsunami and anyone who suggests it's not is incorrect. However Tsunamis are normally not localised but AFAIK they can be localised, it simply depends on the body of water involved and the event causing the tsunami. Megatsunamis is defined as being 'bigger' then the average tsunami but there is no limit to the size of a tsunami, it simply depends on the size and power of what cause the tsunami. So really I can't see any difference between a megatsunami and a tsunami as this article appears to suggest.

Then the article hasn't been written properly. A megatsunami occurs when there is a large displacement of water because of a mountainside or ice falling into it, and typically occurs in a closed channel, i.e. a fjord or other steep, narrow bay; if such a slide or debris-fall or ice-collapse occurs in constrainted waters, the wave can be over a mile high, although it dissipates rapidly after it leaves the fjord. A regular tsunami is rarely more than 30m in height and is not caused by displacement, but by subsidence/shockwave compressions within the body of water. Skookum1 08:03, 8 February 2006 (UTC)


From the current description, it appears to me that this non-scientific term is simply referring to a special case tsunami, specifically a very large tsunami,

It is not a non-scientific term - a rare Greek-Japanese hybrid form - and was coined by the geologists/geographers or whatever they were who charted the aftermath of the Lituya Bay incident).Skookum1 08:03, 8 February 2006 (UTC)

Sorry to disappoint you but "Mega-tsunami" is not a scientific term. It was coined by the BBC when they screened the programme "Mega-Tsunami Wave of Destruction" BBC2 and the programme was broadcast 12 October 2000. It is used by geologists when dealing with the public to explain that the phenomena will exceed anything we have experienced before. It is not used in the scientific press except as in the following example "... a so called mega-tsumnami ..." to clarify that a tsunami with an initial wave of incredible amplitude may be generated. The Geologist (talk) 20:37, 5 March 2008 (UTC)

possibly localised and given the size most likely not cause by seismic activity (although I suspect most people who use the term will call a very large tsunami caused by seismic activity a megatsunami). If I am correct, it's probably best to correct the article to clarify that a megatsunami is simply a losely defined term used primarily by the media, to describe a tsunami of a particularly large size and destructive power, most likely not the result of seismic activity. Or something along that line... Personally, if my understanding is correct, I thing the megatsunami is a rather stupid term. Nil Einne 11:11, 8 January 2006 (UTC)

IMHO, having worked with classifying natural disasters for a government where tsunamis are a threat, this page should ideally be removed (or else it should be a page on popular misconceptions, not natural disasters). It is simply a question of magnitude, not a different phenomenon. --Lindorm


I agree with Lindorm. How does one post an official alert(?) that this article would be merged into tsunami?
One doesn't need to be a geologist to quickly find out that this article and the tsunami article contradict. Among the most jarring phrases was: "Megatsunamis are related to tsunamis in name only: they do not usually have the same cause or appearance." However if you'd go to the tsunami page, you will find out that tsunamis include all the causes of "megatsunamis." Furthermore (as pointed out by TigerShark), parts of the article DO refer to megatsunamis as tsunamis. I didn't see FT2's corrections. The issue seems frivolous even on the semantic level... megatsunami.
I clarified several ambigious phrasings, and edited out a couple of paragraphs in the beginning, I believe the article lives much better in accordance with the tsunami article. --Binba 07:11, 14 November 2006 (UTC)

IMO wave nomenclature needs to be updated in general. Tsunami literally means "harbor wave", and should only be used to say such. To imply source, one should use terms like seismic, impact, landslide, volcanic, tidal, storm, current or focus and avoid the ambiguous terms like tsunami, megatsunami or rogue.

[edit] Image added is not of Megatsunami but Tsunami

I took the image entry out; it should be on the tsunami page. A megatsunami is caused by landslips falling into the ocean, not landslips beneath the ocean. An illustration for this article would best be of Lituya Bay or whichever it was in Alaska which had the 5000'er back in the 1950s; there's images of the debris path, i.e. the wiped-out trees up to the elevation of the wave.Skookum1 08:03, 8 February 2006 (UTC)

Not necessarily caused by landslips. Theoretically almost anything could generate a larger than normal tsunami and that includes an underwater explosion, submarine volcanic eruption generating failure of the edifice - Loihi has undergone some failure, impact by a bollide into the ocean, large landslide entering the ocean with sufficient force and velocity - slow failure of slopes into the ocean will only generate localised large waves which may locally resemble a tsunami. The force present in a tsunami will only dissipate slowly. The Geologist (talk) 15:20, 11 March 2008 (UTC)

[edit] Chicxulub Megatsunami

Anyone have any info about how high the waves were after the comet that killed the dinosaurs hit?--Threedots dead 22:50, 4 March 2007 (UTC)

Try this: Xmax = 0.06 (Ho^4/3 / n^6)

where:

The symbol ^ is used to indicate that the parameter is raised to that power - e.g; H^2 means H squared or H times H. Ho is the wave height (in metres) at the coast in meteres n is the surface roughness typically between 0.015 and 0.07

So without doing the maths for you, you can back engineer the formula to find out how high the waves were by finding out the known distance that the wave inundated. Lets say you will find it interesting! Oh the calculation is incredible and in metres

You might like to look at the following pages: (http://www.nerc-bas.ac.uk/tsunami-risks/html/Phy3Impact.html) and (http://w3.salemstate.edu/~lhanson/gls214/gls/214_waves.html) The Geologist (talk) 20:34, 5 March 2008 (UTC)

[edit] Geohazard?

This is only peripheral to the subject(s) of this discussion, but there is no geohazard article, which I find strange; is tehre something else those are called that could be redirected to? As far as mega/tsunami geohazards, there are three specific ones in my part of the world (BC) - the conseuqnces of what's called The Barrier letting go into Daisy Lake and unlesashing a debris wave into Howe Sound, the potential/probable subsidence of Richmond, British Columbia in the even of "The Big One", and a chunk of Mount Breakenridge at the upper end of Harrison Lake, which like the Barrier could cause devastation far from the location of the event itself in that case, potentially as far as Bellingham Bay....). Anyway no doubt there's no "potential megatsunami" section (or potential avalanche-caused wave or whatever); there must be a catalogue of such hazards somewhere; List of geohazards?? Maybe??Skookum1 (talk) 19:30, 2 March 2008 (UTC)


== That is because it is already dealt with == A list of geohazards includes "Tsunamis," but not "Mega-tsunamis." That is because scientifically and geologically there is no such thing. Since it does not exist scientifically or geologically it cannot present a hazard in any shape or form. The term "Mega-tsunami" was coined by the media - and the British Broadcasting Corporation was the first to use the term when they broadcast the Horizon programme "Mega Tsunami - Wave of Destruction" BBC2 12th October 2000. The fact that certain geologists / scientist have been recorded as using the term is because they are trying to ensure that the ordinary person (who is generally not scientifically literate), understands that "we" are talking about a tsunami of incredible proportions. The wave from a tsunami will vary in amplitude depending upon many factors and the most important of these is the amount of energy that generates the initial disturbance. The greater this energy the larger the initial amplitude of the wave. Lets assume for a moment that the initial disturbance inputs 20 x10^20 joules of energy into the wave. This will dissipate according to the inverse square root law which states that at a distance from the origin the energy will be dissipated by half. It works like this:

At the origin 2.2x10^25 joules (which is about 6x10^27 watts) were forced into the ocean. If the ocean is about 5000 km wide how much energy will hit the distant coastline? E = ( P / 4 pi D^2 ) where E = the Energy at the distant point in watts per metre squared, P = the original power, pi = 3.142 and D = the distance in metres. By substitution it can be shown that at 5,000,000 metres (5000 km) the energy which will hit the coastline is in the order of 2.0E+07 or 20,000,000 Watts per metre square.

Just as there is no "mega-tsunami" there is no such thing as a "super volcano." Volcanologists refer to super-eruptions to indicate VEI 7 or 8 but again it is media generated and not all volcanologists use it. Also think of how many times you will have heard the term "Tidal wave" used when in actual fact the phenomena being reported was a tsunami and nothing to do with the tides. The Geologist (talk) 20:35, 5 March 2008 (UTC)