[Phsstpok]

Most scientists agree

Most scientists agree that such unsourced assertions are poppycock.

It is not a proven theory, but it is not disproven. Suggesting otherwise is silly.

Some of the early supporting evidence (and most spectacularly hyped claims) from work of Moore and Moore (1984 & 1988) dealing with fossil and shell deposits on Lanai has been adequately explained by uplift over the Hawaii hot spot. But nothing has been disproved.

The mathematical models vary widely about the energy in the collapse of volcanic islands, but the velocity estimates of 40 m/s (Ritter Island model) to 100 m/s (La Palma model) and the huge volumes involved clearly support the propositions that tsunamis (some huge) have occurred and will occur again from such events. Even 1,000 meter tall ones are possible at the outside edge of the models. Think 100 Mount St. Helens occuring at once and most of the volcano, with overall height from it's base greater than Mt Everest, is underwater.

Do you have the slightest idea of the energies involved in the collapse of, say, over half of the island that we now call Oahu unleashed? It left a scar that is at least 800 feet thick and covers nearly 9,000 square miles of the ocean bottom. Yes, the energy dissipated "rapidly" and the 200 foot wave did not extend far beyond the other Hawaiian islands, but it is estimated to have still been 65 feet high when it hit ancient California some 4 1/2 hours later.

The Christmas 2005 tsunami was 10 meters, or 30 feet, max, and it was considerably closer to the event, but earthquake generated tsunami's are limited by the maximum vertical displacement of the earthquake. It's this displacement and it's resultant kinetic energy that is important, not the underlying energy in the earthquake itself. A volcanic island collapse will have several orders of magnitude more inherent and kinetic energy involved than any earthquake ever envisioned.

Check out some university web sites, such as the College of Engineering, Department of Ocean Engineering at the University of Rhode Island, or the presentations at the NSF workshop, Hawaii 30th-31st May, 2003. Look at stuff by Stéphan Grilli, the work of Keating and McGuire, or Day and Ward. There is material that argues both sides, but it is REAL material, not bald assertions without any evidence to back it up.

So please stop making unsourced claims in a scientific debate like "most scientists agree," when they clearly don't.

I'm not a geologist, geophysicist, hydrologist or forensic scientist, nor do I play one on TV. I'm betting there probably are some such experts of each (or related scientific fields) available to us here on FR, but I'll bet pretty heavy that you aren't one.

My goodness! By definition we're on the internet. Can't you even hit Google and do a simple search before posting something? The questions are interesting. Trying to stifle the debate by dismissing things you don't understand as "hogwash" is really, really, boring.

[AaronInCarolina]

A volcanic island collapse will have several orders of magnitude more inherent and kinetic energy involved than any earthquake ever envisioned.

On what do you base this assertion? If you are referring to a mild earthquake, maybe. But when you are talking about a 9.0 on the richter scale earthquake, I think that you are wrong. A volcanic island collapse (and we are not talking about a total collapse with Cumbre Vieja) is a localized event involving a relatively finite volume of dirt and rocks that slide, with varying degrees of speed, into the sea. Now, if you really believe that that can compete with forces that are global in scale, involving the earth's tectonic plates, for 750 miles 1000's of feet deep of water were displaced vertically by as much as 30 feet? For heavens sake, it caused the world alter its natural wobble about its axis. It has permanently changed the length of a day. It caused waves to circumnavigate the globe several times. It caused islands to change their latitude and longitude. Are you seriously suggesting that a partial collapse of Cumbre Vieja would produce effects even remotely comparable to this (let alone dwarf the effects of the Indian Ocean tsunami?

Like you, I am not a geophysicist or geologist, but I am an engineer who has studied enough science and physics to form the conclusion that Simon Day's thesis of the effects of Cumbre Vieja is not believable, even in the slightest.

Also, I did not make unsourced claims. I immediately posted a link to the Tsunami Society, which dismisses Simon Day and the Discovery Channel.

but earthquake generated tsunami's are limited by the maximum vertical displacement of the earthquake.

I think that you understate the effect of earthquake-based tsunamis, much as Simon Day and those who believe with him. The potential devatsating effects of a tsunami are not determined just by the maximum vertical displacement. I saw that claim in the Discovery Channel special with Simon Day. They seem to follow the theory that the tsunami produced by an earthquake can only produce a wave as big as the vertical displacement of the water. This suggests to me a fundamental lack of understanding about tsunamis. The thing about tsunamis is the energy that they represent, not the height of the wave at any point. For instance, most tsunamis present themselves as a fairly small wave as the wave moves across the ocean, yet the power of that tsunami is not realized until it approaches shallower waters. To suggest that an earthquake generated by a sub-marine plate that rises from the ocean floor by, say, 30 feet completely ignores the depth of the ocean and the amount of water that is actually thrust upwards. To say that the wave is limited to 30 feet is to almost completely miss the most important factor in a tsunami... the potential energy that has been converted from plate stress to a lateral pressure wave of water where the amplitude of the wave is a fairly unimportant. For example, you could have a massive earthquake where the sea floor only raises a foot or two, but if happens at a depth of, say, 10,000 feet and the surface rises by a foot or two, then that should generate a much more powerful tsunami than one where the sea floor rises higher but at a shallower depth of water. The strength of the tsunami is proportional to the amount of water displaced, and that is a funtion of the depth of the sea where the sea floor rose. You also must factor in the length of the plate boundary where the earthquake occurred, in the case of the Indian Ocean, about 750 miles. If the Indian Ocean quake had been more of a point event, it would likely have been a much less devastating event. A point event, like a landslide-generated tsunami, produces more of a circularly radiating wave, which means that the energy dissipates in an inverse-square function. In other words, it cannot keep the same potential devastation regardless of the distance from the source because the area grows accordin g to the square of the radius. In the case of the Indian Ocean tsunami, the event was not a point event, it was a line event, and the resulting energy propagated mostly in an east-west fashion due to the north-south line of the tectonic plate boundary. This resulted in a largely linear propagation of the energy, rather than a radial propagation (as would happen with La Palma), and therefore the energy did not dissipate so much due to distance. It is a highly simplistic approach to say that because a landslide-based tsunami would generate a larger (probably much larger) surface wave at the source, that that compares with a much smaller wave at the source generated by a deep-ocean sea floor rise earthquake. Though it may be a larger wave at the surface, its not the height of the wave, its the energy behind the wave.

These principles of physics are largely ignored by the theories I have read. I have read Simon Day's paper that was the basis of the Discovery Channel. I found that he ignored these physical principles. He seemed to assume that a wave of one particular height could be compared with a much different wave of a lesser surface height (but much greater depth) as apples to apples. They are not.

Believe what you want. I can read both sides and decide to chose one over the other. By the way, I am quite capable of googling. And I did do a Google search prior to my post. Just because you disagree with me, you don't have to belittle my argument. Please state what YOU actually believe and discuss the details rather than just say that there are people who believe both ways.