The death toll keeps rising. The number of dead becomes more and more unreal, and horrible. I have had numerous phone calls from friends, saying, “Dude, didn’t you just dream about tidal waves wiping out the planet a couple weeks ago?” Yes, I did. I feel weird about it, to be honest. I know I didn’t cause the wave, I mean, of course … but it still is kind of odd. I have recurring tidal wave dreams, but by ‘recurring’ I mean – once a decade or so. Every time I have a tidal wave dream, I pay close attention … and to have written numerous posts, one which was entitled: “The Tidal Wave – Let it come” a mere 2 weeks ago…. it’s just a bit creepy.
In all of the news articles I have read, though, the actual size of the wave is not mentioned. They say “massive”, etc., and obviously from the damage done it had to be enormous (or at least – very very powerful and fast-moving). Does anyone know how tall this wave actually was?
Also, I know there is a difference, but … what’s the dif. between a tsunami and a tidal wave?
The latest number on Yahoo Headlines is 59,000. Horrible.
As far as I’ve learned, there’s no difference between the two – one’s just a fancier sounding furrin’ word.
This is so horrible I can barely think straight.
Red, glad you’re back – and oh my God, your post about waves has me shivering.
Here’s general info on Tsunamis:
Tsunami comes from the Japanese tsu (harbor) and nami (wave). Appropriate naming, as some 80 percent of all tsunamis occur in the Pacific Ocean and Japan has suffered many, some coming from as far away as South America. Tsunamis are often incorrectly called tidal waves, but tides have nothing to do with them (though the damage may be worse if a tsunami hits at high tide).
A tsunami (pronounced tsoo-nah-mee) is a wave train, or series of waves, generated in a body of water by an impulsive disturbance that vertically displaces the water column. Earthquakes, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites, can generate tsunamis. Tsunamis can savagely attack coastlines, causing devastating property damage and loss of life.
Tsunamis are unlike wind-generated waves, which many of us may have observed on a local lake or at a coastal beach, in that they are characterized as shallow-water waves, with long periods and wave lengths. The wind-generated swell one sees at a California beach, for example, spawned by a storm out in the Pacific and rhythmically rolling in, one wave after another, might have a period of about 10 seconds and a wave length of 150 m. A tsunami, on the other hand, can have a wavelength in excess of 100 km and period on the order of one hour.
As a result of their long wave lengths, tsunamis behave as shallow-water waves. A wave becomes a shallow-water wave when the ratio between the water depth and its wave length gets very small. Shallow-water waves move at a speed that is equal to the square root of the product of the acceleration of gravity (9.8 m/s/s) and the water depth – let’s see what this implies: In the Pacific Ocean, where the typical water depth is about 4000 m, a tsunami travels at about 200 m/s, or over 700 km/hr. Because the rate at which a wave loses its energy is inversely related to its wave length, tsunamis not only propagate at high speeds, they can also travel great, transoceanic distances with limited energy losses.
Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the earth’s crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. Waves are formed as the displaced water mass, which acts under the influence of gravity, attempts to regain its equilibrium. When large areas of the sea floor elevate or subside, a tsunami can be created.
Large vertical movements of the earth’s crust can occur at plate boundaries. Plates interact along these boundaries called faults. Around the margins of the Pacific Ocean, for example, denser oceanic plates slip under continental plates in a process known as subduction. Subduction earthquakes are particularly effective in generating tsunamis.
A tsunami can be generated by any disturbance that displaces a large water mass from its equilibrium position. In the case of earthquake-generated tsunamis, the water column is disturbed by the uplift or subsidence of the sea floor. Submarine landslides, which often accompany large earthquakes, as well as collapses of volcanic edifices, can also disturb the overlying water column as sediment and rock slump downslope and are redistributed across the sea floor. Similarly, a violent submarine volcanic eruption can create an impulsive force that uplifts the water column and generates a tsunami. Conversely, supermarine landslides and cosmic-body impacts disturb the water from above, as momentum from falling debris is transferred to the water into which the debris falls. Generally speaking, tsunamis generated from these mechanisms, unlike the Pacific-wide tsunamis caused by some earthquakes, dissipate quickly and rarely affect coastlines distant from the source area.
Similarly:
“A tsunami (from Japanese meaning wave in port or “harbour wave”) is one or a series of deep water ocean waves that can occur after a large earthquake (having a vertical component of movement), seaquake, volcanic activity, landslide, slumps, or meteorite impacts in or near the sea. Tsunamis are sometimes referred to as tidal waves as they often resemble a tide that keeps rising, rather than cresting waves when they reach shore. However, the term is misleading as tsunamis are not caused by tides, and its use is being discouraged by oceanographers. While it has also been noted that tsunamis often have little to do with harbors (despite the Japanese translation of the word), the term “tsunami” is used exclusively to refer to water surges caused by physical displacement of water and is thus more correct.
It is probable that the Japanese term was first coined because surges would have the greatest impact, and be most widely witnessed in coastal population centres, which are often built around natural harbours, rather than in sparsely populated or unpopulated areas.
Evidence shows that megatsunamis, which are caused by significant chunks of an island collapsing into the ocean, are also possible.
Related to a tsunami is a seiche. Often large earthquakes produce both tsunamis and seiches at the same time. In addition there is evidence that some seiches have also been caused by tsunamis.”
This and much more available at the Wikipedia.
Okay, help.
might have a period of about 10 seconds and a wave length of 150 m. A tsunami, on the other hand, can have a wavelength in excess of 100 km and period on the order of one hour.
I don’t know what you’re talking about. Because I’m dumb at math. Help?
So a tsunami can basically be not very tall, not like a huge wall of water, and travel across long distances … and then when it hits a shoreline, it rises up. Is … that right?
The thought of it is just terrifying.
What’s a “period”, in your context, Stevie? How long the wave lasts before crashing?
Oh, and also – how long after the earthquake did the waves hit, say, Sri Lanka?
I know they have no warning system set up – but would there have time to warn anyone if there had been a system set up?
As I understand it, Sheila, a tsunami is just a giant wave, the term is Japanese – meaning ‘wave in port'(?), and is generally interchangeable with ‘tidal wave’ although tsunami are, I think, generally associated with earthquakes.
This time the initial wave that hit the closest coast was reported as up to 10 metres high.. but that figure will vary according to where it hit the coast (10m at Sumatra, 6m at Sri Lanka), and waves reached the African coast too – no real measurements were recorded so it’s all estimates based on the geological data and eyewitnesses.
It not just the height that does the damage, it’s the speed as well.. travelling in the ocean one source says that the wave could reach up to 500km/h.. that slows as it travels into shallower regions close to land (down to 50km/h in some places).
Then there’s the following waves of lesser intensity and others caused by the aftershocks.
It’s the huge mass of water traveling at sped that causes the damage, when you combine the groupings of populations along coastlines, or on low lying islands, the result is the number of fatalities we are seeing.
Next time you are in the bath, don’t move and when the water becomes very still, lift your leg and watch what happens. Imagine the two ends of the tub as land masses. Alternatively, you can imagine if you were to pick up one end of the tub and put it back down. When you have it up, all the water goes to the other end; when you put it back down, you get a great rush of all the water that has been displaced.
Probably not totally accurate but gives you an idea of the dynamic. They are getting the other end of the tsunami in Somalia and Kenya.
I see most of my points were already made.. I can maybe help out on some of the time questions.. the first wave hit Aceh the closest land to the epicentre at 8.25am.. 25 minutes after the earthquake. So for other areas, say Sri Lanka, there would probably have been at least a couple of hours.. depending on where the warning sensors were positioned but the closest regions would not have had enough time to do anything.
And the period of the series of waves would be the time between peaks.
Period: how long it takes for one complete wave to pass.
Wavelength: how long, horizontally, one complete wave is.
The height of the wave above sea level would be the amplitude.
Picture and text here for explanation of the basic terms.
The period would be the time between waves.
Boing Boing has a link to an animation of the tsunami (http://www.boingboing.net/2004/12/27/animations_of_tsunam.html) that shows where the waves were with an elapsed time indication.
Here’s an interesting link sent to me by Stevie – thanks! It’s about the development of tsunami warning apparatus, happening in Seattle.
The number is beyond comprehension, I can’t get my head around the idea of 60,000 people wiped out by a tidal wave.
But I wish the media would stop dwelling on the swimsuit model who lost her husband. I know there’s a desire to put a human face on such a massive tragedy, but can we not choose a vacationing model?
Yeah, that Czech chick is a headline on Yahoo News. Bothersome.
A human face to the tragedy? For me, this woman’s obvious despair and loss is human enough, even though she’s not some stupid model.
We all have these theatrical images of crashing waves, but from the video taped images that they’ve been broadcasting it really looks like a surge of fast moving water. And the person who made the bathtub analogy probably gave the best example that’s not overly scientific.
The storm surges that hit coastal areas during Hurricanes are a similar type of phenomenon, except the wind is what pushes the water ashore, as opposed to the earth moving up or down. This is why during hurricanes they warn people that the winds are not what they need to fear, but the water coming in behind it.
Either combination is deadly. An early warning system could have definitely saved lives. The really tragic part is most people who were swept away had no idea it was coming. Many who survived were simply lucky.
Needless to say, nature in it’s fury is a humbiling force to be reckoned with.
On a different note….love the new look…almost thought I’d landed on the wrong site when I entered the URL.
Sheila, you’re at least partially right about the wave “rising up when it hits the shoreline,” if I may paraphrase. That’s one of the things that makes crossing a shoal in a boat potentially dangerous. Your boat might be shallow enough draft that grounding isn’t a risk, but the nature of the waves change as the water rapdly shallows. Those nice rollers in deeper water suddenly become taller, short-period waves that can smash out your pilot-house windows in an eyeblink, “poop” you (large volume of water coming aboard over the stern), or even knock over your boat, possibly introducing you to the unpleasant term “downflooding.”
Wind-driven waves are different, as peteb and Linus and the others have said. They don’t move as fast as tsunami, but the maximum theoretical height (amplitude) of a wind-driven wave is something 198 feet. That’s the point of the climactic scene aboard the Andrea Gail in The Perfect Storm.
No wave that height has ever been observed, to my knowledge; no observer would live to make a report.
The individual stories coming out of Thailand and Bangladesh now are just horrific. Having two small boys and liking to sail and vacation on the Outer Banks, I think about this stuff from time to time.
I suppose any wave that theoretically could reach 198 feet, would also bust any measurement device trying to record it.
Shivers. Just awful to contemplate.
Carrie –
Love the bathtub analogy. I can see it in my mind right now. I will try it tonight. (I will make sure to remove all Lush products from the vicinity, however. LOVE that stuff, by the way. The chunky sleep-inducing soap, etc. I’ve been using it obsessively.)
Fee –
One of our mutual friends headed up the re-design. But don’t say her real name here if you guess!! I love what she did.
Roger that Red….actually she told me she was helping out with the revamp.
:)
OMG – the stories of that friggin’ model – as headlines. I’m terribly sorry for her suffering, but no more than the millions of others who are affected by this. I refuse to accept that somehow her loss and injury is more important because she’s a pretty skeleton that gets her picture taken for a living. This represents the worst of vacuous celebrity worship and my patience with the entire notion is getting thin.
One of the other things we talked about here lately was huge scary things in the ocean. Sometimes the huge scary thing is the ocean.
Emily –
Her headlines are different than the regular old “This many number of locals were killed in the tidal wave” that you will see in many local newspapers. That’s local interest – people want to know that stuff – and knowing that a couple people from your hometown or your region were affected is fine, that’s real local news.
But on Yahoo right now – there are two photos of the hot Czech model on display (in Victoria’s Secret) – and one photo of a screaming Sri Lankan woman. Nope. That ain’t right.
skillzy –
The waves generated by “the perfect storm” in 1991 were of that huge variety. I was in Rhode Island on the day that storm hit out to sea – you can’t imagine the storm surge. It wasn’t NEARLY as violent as what was happening far far out in the ocean – but we could definitely feel the effects, and just looking at the turmoil made me think: “jesus, if it’s this crazy here … what the hell is it like out there?”
Sheila, regarding your question about a warning system: Wretchard has an interesting post up at Belmont Club showing an excerpt from the log kept by the Pacific tsunami warning system that tracked this event. Although there was enough time to issue warning, there was apparently no-one attendant who understood the implications this event would have for coastal regions of the Indian Ocean. Or the failure to forward a warning might have simply been due to bureaucratic inertia. Regardless, even if the alarm had gone out, there was apparently no mechanism in place to disseminate the news or in any other way transform this information into useful action.
That’s what I mean, Sheila. If the story were run on Models Weekly or a Czech site, like you said, fine. It’s news. Maybe after the flood of truly awful figures settles and the numbers are in, it might merit a mention that this semi-famous person was among the victims in the regular news. But not now.
“Hot Chick Among Victims!” Screw you, Yahoo.
carrie, you’re according to a geologist on cnn, you’re exactly right with your bathtub analogy. that was his way of describing it to those of us laypeople who tend to have the wrong idea about tsunamis. they’re calling this one of (if not the)biggest natural disasters in history and the true ramifications for the countries hardest hit will not be seen for years to come. i am horrified.
Emily – yup. Disgusting.
CNN has a tragic picture on their front page, this one. God, I hope this kid has someone who can look out for him.
What about the little baby found floating on a mattress – and they actually located his parents in all the chaos? Unreal.
God, Bill. That’s horrible. Hopefully relatives of his somewhere will see the photo and contact the proper people.
Comprehension
The concept of what a tsunami is is very hard to comprehend. But this quicktime video helps. And this animated gif helps the understanding even more.Source of links here. Found the link to BoingBoing in the comments of this post.
this photo, too…
Sheila, the only figure I’ve heard quoted is 50 meters.
red, did you say you were going to move all the plush toys away from your tub…
Comprehension
The concept of what a tsunami is is very hard to comprehend. But this quicktime video helps. And this animated gif helps the understanding even more.Source of links here. Found the link to BoingBoing in the comments of this post.Update : Sha