The Coming Atlantic Mega-Tsunami 1068
rbrander writes "It's not news at all that scientists predict an eventual "mega-tsunami" that will sweep across the Atlantic that will still be anything from 60 to 150 ft high when it hits the U.S. Eastern seaboard. This Old News, however, suddenly seems fresh. Like an asteroid hit, it could be millenia away, or tomorrow, that a volcano in the Canary Islands just off Africa drops half a trillion tons of rock into the Atlantic.
A short description of the problem from BBC News and some more graphic descriptions (of up to 100 million dead) and shrewd commentary on the politics of warning from journalist Gwynne Dyer."
Videos of Asian Tsunami... (Score:5, Informative)
Wikipedia (Score:5, Informative)
"During an eruption that is anticipated to occur sometime within the next few thousand years the western half of the island, weighing perhaps 500 billion tonnes, will catastrophically slide into the ocean. This will inevitably generate a megatsunami which will travel across the Atlantic and strike the Caribbean and the Eastern American seaboard several hours later with a wave possibly 90 meters (300 feet) high, resulting in massive coastal devastation.
Re:Early warning (Score:4, Informative)
Some bad science in the post (Score:5, Informative)
They don't get big until they approach the shore and the depth gets shallow.
The small waves, btw, travel around the speed of a jetliner, hence the lack of warning.
armageddon (Score:2, Informative)
Re:Early warning (Score:5, Informative)
At least in the Atlantic, we have an early warning system for Tsunamis
Untrue. The Pacific has the only dedicated system (although Tsunamis may be inferred from other equipment like tidal gauges.)
I assume this has been contemplated, but couldn't we cause the threatening hunk of rock to slide in a safer direction? Like cutting down a tottering tree?
Wave Height (Score:5, Informative)
I heard an interview with someone from NOAA with the Pacific Marine Environmental Laboratory in Seatle that described what happens when a Tsunami occurs. He said when the wave travels through deep water it has tremendous speed (hundreds of mile/hour) but is only a few feet high. As it comes into shallow water the wave slows down to 10s of miles/hour and that causes the huge wall of water. So a Tsunami is not really a 100 ft wave as it travels through the ocean only once it nears land.
Just my $.02.
Re:100 million? (Score:3, Informative)
If it would wrap around Florida, you could include the populations of Tampa, New Orleans and Houston (among others) for probably another 10 million.
Add in the populations of most, if not all, of the Carribean and the Canadian seaboard and you're probably now talking in excess of 75 million potential victims.
Keep in mind, in the U.S. about 2/3 of the population lives east of the Mississippi.
-Charles
Links to Researchers (Score:5, Informative)
Now I can change my
OVER-HYPED (Score:4, Informative)
Tidal wave thread 'over-hyped' [bbc.co.uk]
Summary: Evidence suggests slides on the Canary Islands to happen in small, incremental slides. The huge collapse is sensationalism and the absolute "worst-case scenario"
Re:Videos of Asian Tsunami... (Score:3, Informative)
Add
Bad computer models exagerate La Palama tsunami? (Score:5, Informative)
That's a three foot wave hitting the U.S. Eastern seaboard after a worst case collapse at La Palma. The paper is very detailed and worth a read.
Re:Early warning (Score:3, Informative)
US Midwest not so safe either... (Score:2, Informative)
Re:Videos of Asian Tsunami... (Score:5, Informative)
Lots of hype, poor science (Score:5, Informative)
read it [noaa.gov] and learn something.
Note that one could point to a lot of active oceanic volcanoes and pose a similar threat level if one considers a tens of thousand of years time frame.
Another side note: When I was in grad school, I was the TA for one of the committee members.
Re:Finally, a good use for Florida (Score:1, Informative)
Re:Early warning (Score:3, Informative)
Modelling by colleagues in Switzerland shows that such a landslide could trigger a so-called mega-tsunami, which has an initial wave height of 650 metres (2,130 feet) and moves out over the ocean at speeds up to 720 km/h (450 mph).
By the time such a wave crossed the Atlantic, its power would have diminished but it could still wreak havoc up to 20 kilometres (12 miles) inland.
And from the Questions and Answers section:
Scientists also know that a collapse will not happen without any warning. They will be able to alert people to possible danger several weeks in advance.
So we've got a few weeks to move (several hundred million) people 20 kilometers. Still a huge operation but it should be possible.
Re:Wikipedia (Score:5, Informative)
See Tidal wave threat 'over-hyped' [bbc.co.uk] at the BBC web site, and this statement [sthjournal.org] from the Tsunami Society:
....Volcanoes on La Palma ... and Hawaii", George Pararas-Carayannis, in Science of Tsunami Hazards, Vol 20, No.5, pages 251-277, 2002.
MEGA TSUNAMI HAZARDS
January 15, 2003
The mission of the Tsunami Society includes "the dissemination of knowledge about tsunamis to scientists, officials, and the public". We have established a committee of private, university, and government scientists to accomplish part of this goal by correcting misleading or invalid information released to public about this hazard. We can supply both valid, correct and important information and advice to the public, and the names of reputable scientists active in the field of tsunami, who can provide such information.
Most recently, the Discovery Channel has replayed a program alleging potential destruction of coastal areas of the Atlantic by tsunami waves which might be generated in the near future by a volcanic collapse in the Canary Islands. Other reports have involved a smaller but similar catastrophe from Kilauea volcano on the island of Hawai`i. They like to call these occurences "mega tsunamis". We would like to halt the scaremongering from these unfounded reports. We wish to provide the media with factual information so that the public can be properly informed about actual hazards of tsunamis and their mitigation.
Here are a set of facts, agreed on by committee members, about the claims in these reports:
- While the active volcano of Cumbre Vieja on Las Palma is expected to erupt again, it will not send a large part of the island into the ocean, though small landslides may occur. The Discovery program does not bring out in the interviews that such volcanic collapses are extremely rare events, separated in geologic time by thousands or even millions of years.
- No such event - a mega tsunami - has occurred in either the Atlantic or Pacific oceans in recorded history. NONE.
- The colossal collapses of Krakatau or Santorin (the two most similar known happenings) generated catastrophic waves in the immediate area but hazardous waves did not propagate to distant shores. Carefully performed numerical and experimental model experiments on such events and of the postulated Las Palma event verify that the relatively short waves from these small, though intense, occurrences do not travel as do tsunami waves from a major earthquake.
- The U.S. volcano observatory, situated on Kilauea, near the current eruption, states that there is no likelihood of that part of the island breaking off into the ocean.
- These considerations have been published in journals and discussed at conferences sponsored by the Tsunami Society.
Some papers on this subject include:
"Evaluation of the threat of Mega Tsunami Generation From
"Modeling the La Palma Landslide Tsunami", Charles L. Mader, in Science of Tsunami Hazards, Vol. 19, No. 3, pages 160-180, 2001.
"Volcano Growth and the Evolution of the Island of Hawaii", J.G. Moore and D.A.Clague, in the Geologic Society of America Bulletin, 104, 1992.
Committee members for this report include:
Mr. George Curtis, Hilo, HI (Committee Chairman) 808-963-6670
Dr. Tad Murty, Ottawa, Canada, 613-731-8900
Dr. Laura Kong, Honolulu, HI, 808-532-6422
Dr. George Pararas-Carayannis, Honolulu, HI, 808-943-1150
Dr. Charles L. Mader, Los Alamos, NM, 808-396-9855
and all can comment on this or other tsunami matters.
For information regarding the Tsunami Society and its publications, visit: www.sthjo
Re:Tsunamis (Score:5, Informative)
A lot, yes. Most, no. Consider New York City. Eight million residents, and millions more day workers. Roads which come to a stop and trains which totally fill just getting the day workers out each evening. People will try to retreat to high buildings and hope the foundations hold (probable, most are attached to bedrock) - but in the outer boroughs homes are mostly just a few stories. Will these folks be welcomed in the skyscrapers even if they get there? Plus, all of Long Island will be trying to evacuate over the same bridges used by the city.
Re:Terrorist (Score:2, Informative)
it would take more then a 'small nuke' to do that anyways... This past quake at 9.0 was equal to 100 million nukes...
Re:Early warning (Score:5, Informative)
The mechanism of exploding mountains, as discovered when Mt St Helens went "bang" is:
- Pressure builds up, bulging the mountain upward.
- Suddenly the bulging causes the side of the mountain to slide off.
- With the weight suddenly removed, the pressure blasts the remaining portion of the mountain into dust and up into the stratosphere.
So IMHO attempting to remove the loose slab, slowly and gently, from the intermittently-active volcano (which is thus inactive now because the weight above it is enough to keep the lava and gas bottled up) very likely WOULD wake it up. If that happens, the part that isn't moved yet might just go right away.
And given that the slab is already slipping off slowly, disturbing it by trying to disassemble it risks finishing the job of loosening it and precipitating the event you're trying to avoid.
Kinda like defusing a BIG bomb. Or taking apart a large pile of jackstraws without having any of them collapse.
new mirror of South Asia tsunami vids (Score:3, Informative)
clicky [photosphere.org]
Re:Oh Damn! (Score:3, Informative)
Anyway, the soil around downtown St. Louis is fairly loose with a lime stone base. If the right type of large earthquake hits in New Madrid, the entire soil base will turn to the consistancy of Jello. Many of the building downtown are still old double rowed brick that would just collapse and even some of the newer buildings wouldn't last.
We have no modern notion of what a 11 or 12 on the richter scale will do...
October 2000? (Score:2, Informative)
Submitter was Wrong (Score:3, Informative)
Re:Oh Damn! (Score:3, Informative)
Re:Wikipedia (Score:5, Informative)
Re:Straight Line Path (Score:3, Informative)
Looks like tsunami waves can diffract like any other kind of wave....
Re:Straight Line Path (Score:2, Informative)
> might wash right over the smaller islands. Even a
> really big wave will only travel a mile or so
> inland, last I checked. YMMV
The 26 Dec Asian Tsunami is reported to have gone 6 km (~3.7 miles) inland in some places and was "only" about 10m (31ft) high, so I draw a different conclusion if the waves predicted here for the U.S. east coast are "20-50m" high.
I would also imagine the height/strength of the structures "softening" the impact plays a role - at 50m height there are much less obstacles which pose any challenge than at 10m.
I'd be pretty scared.
Re:This would be the greatest weapon ever. (Score:1, Informative)
Re:Straight Line Path (Score:5, Informative)
This is highly dependant on wavelength to aperature ratio, which is why you can hear sounds around a corner, but not see around one.
Most scientists agree that this won't happen (Score:5, Informative)
Here are a set of facts, agreed on by committee members, about the claims in these reports:
- While the active volcano of Cumbre Vieja on Las Palma is expected to erupt again, it will not send a large part of the island into the ocean, though small landslides may occur. The Discovery program does not bring out in the interviews that such volcanic collapses are extremely rare events, separated in geologic time by thousands or even millions of years.
- No such event - a mega tsunami - has occurred in either the Atlantic or Pacific oceans in recorded history.
- The colossal collapses of Krakatau or Santorin (the two most similar known happenings) generated catastrophic waves in the immediate area but hazardous waves did not propagate to distant shores. Carefully performed numerical and experimental model experiments on such events and of the postulated Las Palma event verify that the relatively short waves from these small, though intense, occurrences do not travel as do tsunami waves from a major earthquake.
- The U.S. volcano observatory, situated on Kilauea, near the current eruption, states that there is no likelihood of that part of the island breaking off into the ocean.
- These considerations have been published in journals and discussed at conferences sponsored by the Tsunami Society.
Some papers on this subject include:
"Evaluation of the threat of Mega Tsunami Generation From
"Modeling the La Palma Landslide Tsunami", Charles L. Mader, in Science of Tsunami Hazards, Vol. 19, No. 3, pages 160-180, 2001.
"Volcano Growth and the Evolution of the Island of Hawaii", J.G. Moore and D.A.Clague, in the Geologic Society of America Bulletin, 104, 1992.
Wave-front healing (Score:3, Informative)
The result is that a disruption along a wave front can "heal" itself. This means that the undisrupted part of the wave front slowly fills in the disrupted part. The further past the dispruption you are, the less obvious it becomes that a dispruption even took place.
As a result, islands that are far from the coast may not give much protection.
Also note that bays and inlets can serve to focus and guide the wave energy. For example, a tsunami once reached Port Alberni on Vancouver Island. Here's a map http://www.travelamap.com/canada/centralisland.htm [travelamap.com].
Read it and weep.
Re:Oh Damn! (Score:5, Informative)
A magnitude 12 would be 160 trillion tons equivalent, and would "fault Earth in half through center."
Not even bad science, it's uninformed speculation (Score:1, Informative)
But there is a speed limit, and thus a limit on the energy transmitted. Wave action is normally a very efficient way to transmit energy. But once the surface wave goes above 0.7-0.8 Mach of the air above, the energy is spent misting and roiling the water. Thus a huge surface event will only be locally more destructive, and perhaps will not couple nearly as much energy into a wave.
The most effective way to couple massive energy into the ocean is as a pressure wave. To avoid wasting energy by forming voids and boiling water, it's best done in very deep water where the pressure is high and the energy spreads widely before becoming a surface wave. Now think back to the news reports -- this recent quake happened at over 10 kilometers sea depth. It likely coupled as much impulse energy as the ocean would handle at that (relatively deep) depth.
Another consideration is the wave reflective effect of the Atlantic ridge. With a gradual bottom slope most of the energy is converted to a slower, steeper wave. With a ridge much of the energy is reflected, resulting in a more gradual surge.
There are a bunch of other factors, but basically "it can't happen here" isn't as far off as you might think. (Statement applys to U.S. East coast residents only -- no one else matters
Re:Early warning (Score:2, Informative)
You seem to have missed the most cogent lesson of this disaster - there is no early warning system in the pacific either.
This had nothing to do with weather systems, this was a seafloor seismic event. However, it would seem that not having an early warning system is not an accurate indicator of low seismic activity. After all, prior to 2001, the chances of an aeroplane flying into a skyscraper were pretty low, no?
The fault on Gran Canaria is well-documented over a long period.. calculations have been carried out that show exactly what would happen if the entire fault gave way, and believe me, the eastern USA would consider Florida's recent hurricane to be fairly trivial in comparison..
Putting your head in the sand will not help much when the sand is under 10ft of water.....
Re:Oh Damn! (Score:2, Informative)
Slashdot lemming moderators strike again (Score:2, Informative)
http://news.bbc.co.uk/1/hi/sci/tech/3963563.stm
http://personal.telefonica.terra.es/web/iberiana
Technical details (Score:4, Informative)
Massonetal01_ESR.pdf [geo.ub.es]
in general, once the waves hit the open ocean, it IS a straight line path. Islands will tend to absorb waves, "creating shadow patterns". There is an excellent analysis here:
GRL- Cumbre Vieja Volcano -- Potential collapse and tsunami at La Palma, Canary Islands (PDF) [ucsc.edu]
complete with illustrations that demonstrate that the Bahamas protect Miami, if not much else.
Re:Videos of Asian Tsunami... (Score:3, Informative)
Re:Oh Damn! (Score:3, Informative)
The logarithmic aspect of it is actually how much it causes the seismograph to move, not the amount of energy released. This most recent quake caused a 600 mile wide section of the Earth's crust to move 10-15 feet. A magnitude 11 earthquake is just not possible, at least with normal plate tectonics.
Re:Oh Damn! (Score:3, Informative)
Not on this planet.
Measuring Earthquake Magnitudes [about.com]: 'It seems that earthquakes on Earth simply can't get bigger than around Mw = 9.5. (That means the whole premise of the TV series 10.5 is bogus.) A piece of rock can store up only so much strain energy before it ruptures, so the size of a quake depends strictly on how much rock--how many kilometers of fault length--can rupture at once. The Chile Trench, where the 1960 quake occurred, is the longest straight fault in the world. The only way to get more energy is with an asteroid impact.'
US Geological Survey [usgs.gov]: 'The idea of a "Mega-Quake" - an earthquake of magnitude 10 or larger - while theoretically possible--is very highly unlikely. Earthquake magnitude is based in part on the length of faults -- the longer the fault, the larger the earthquake. The simple truth is that there are no known faults capable of generating a magnitude 10 or larger "mega-quake."'
More recent BBC article (Score:3, Informative)
http://news.bbc.co.uk/1/hi/sci/tech/3963563.stm [bbc.co.uk]
Re:Bah, this is nothing compared to when (Score:2, Informative)
Yellowstone Volcano Observatory FAQs [usgs.gov]
" The least likely but worst-case volcanic eruption at Yellowstone would be another explosive caldera-forming eruption such as those that occurred 2.1 million, 1.3 million, and 640,000 years ago. However, the probability of such an eruption in any given century or millennium is exceedingly low- much lower than the smaller eruptions..."
and
"Is it true that the next eruption of Yellowstone is overdue?
No. The fact that two eruptive intervals (2.1 million to 1.3 million and 1.3 million to 640,000 years ago) are of similar length does not mean that the next eruption will necessarily occur after another similar interval. The physical mechanisms may have changed with time. Furthermore, any inferences based on these two intervals would take into account too few data to be statistically meaningful. To say that an eruption that might happen in ten's or hundred's of thousand's of years is "overdue" would be a gross overstatement. On the other hand we cannot discount the possibility of such an event occurring some time in the future, given Yellowstone's volcanic history and the continued presence of magma beneath the Yellowstone caldera."
Re:This would be the greatest weapon ever. (Score:2, Informative)
Which in a way is really dumb, because the pressure down there is building. Letting it out in lots of small slips is better than having it go off in a big one.
This isn't necessarily true. The reactivation of small faults by an increase in the pore fluid pressure is a well known effect.
It's most common after constructing reservoirs: the wave of increasing pore fluid pressure in rocks under the reservoir, rather than the extra weight or any special property of the water (any fluid would do the same thing), causes small quakes.
The pressure down there is not, however, necessarily building. It is entirely reasonable, in some cases, to expect that no quakes would occur without the increase in isostatic pressure. There can be constant stress on a fault where that stress is simply to low to cause earthquakes under normal circumstances, but where the increase in differential stress by an increase in fluid pressure is just enough to reactivate it. This also suggests that in many such cases there isn't sufficient stress to produce large earthquakes. Furthermore, many faults simply aren't large enough to produce large earthquakes irrespective of fluid pressure. And finally, it doesn't follow that many small quakes will necessarily relieve stress and prevent a large one.
Fortunately, despite the rabid idiots screaming nonsense in the popular press, it is unlikely that the collapse of the island would actually produce a major tsunami, thus any questions of nukes, pumping water in to the rift, pumping water out of the rift, or volcanic eruption are unlikely to matter too much to anyone living any reasonable distance from the island.