Why don't they call the tsunami a tidal wave?

[MikeG]

It would be plainer.

[Ediacara]

1. Tidal waves are caused by tides, tsunami's aren't

It would be like calling an earthquake an "indistrial accident."

[MikeG]

3. So the Bangladesh tidal wave wasn't caused by an earthquake?

[Ediacara]

4. I'm not sure I follow?

What do you mean?

[MikeG]

5. In the 70's Bangladesh was hit by a tidal wave killing 300,000.

Was that just a tide?

[Ediacara]

11. I don't know

I don't know anything about it, sorry. In the past, tsunamis have been called tidal waves by the news media, but that practice is wrong and is being mostly phased out now.

Tidal waves are caused by tidal forces, tsunamis are caused generally by earthquakes, but can also be caused by landslides. If 300,000 people died, I suspect that it was probably a tsunami.

Note though... tsunamis can be greatly amplified or diminished by local tidal conditions. In other words, if the tide is going out, a tsunami's effect will be lessened, and if the tide is going in, it will be amplified.

[starroute]

17. That one was caused by a cyclone

And technically it was not a tidal wave but a storm surge, like you might get with any hurricane.

There's more than you'd want to know about cyclones in the Indian Ocean at http://www.imdmumbai.gov.in/cycdisasters.htm . Here are a few factoids:

The oldest and the worst cyclone on record is that of October 1737 which hit Calcutta and took a toll of 300,000 lives in the deltaic region. It was accompanied by a 12 metre high surge. A violent earthquake coinciding with this storm enhanced the destruction.

Bangla Desh Cyclone of 8-13 November 1970 which crossed Bangla Desh coast in the night of 12th was one of the worst in recent times, with storm surges of 4 to 5 metres height at the time of high tides, and with 25 cm of rain in the areas, the inundation took toll of about 300,000 people.

Andhra Cyclone of 14-20 November 1977 that crossed coast near Nizampatnam in the evening of 19th, took a toll of about 10,000 lives. The Ship Jagatswamini, which went right into the eye of the storm in the evening of 17th experienced maximum wind speed of 194 kmph. As the storm approached the coast, gale winds reaching 200 kmph lashed Prakasam Guntur, Krishna, East and West Godavari districts. Storm surge of 5 meters high inundated Krishna estuary and the coasts south of Machilipatnam.

While we're at it, there's a handy table of pre-1900 disasters and their toll at http://www.insurance.com.my/zone_themii/e-jirm/archives/2000/millenniumreview_table01.htm . The current one, horrific as it may be, is far from being the worst ever.

[The Magistrate]

6. The Term 'Tidal Wave', Sir

Was formerly in use, but has been dropped as it can lead to confusion, and originated in misnomer. There is something "tidal" about the action of a tsunami at the shoreline, and people were originally ignorant of the actual cause. Tsunami is simply a foriegn word, Japanese, if recollection serves, for "tidal wave", that has been adopted to distiguish waves resulting from underwater shocks from any other possible sort of wave. The older form, of course, continues on occassion in use, and thus provides a fresh source of confusion....

[MikeG]

7. That you for clearing that up, sir.

[Bluebear]

10. Japanese for "harbor wave" I believe

And it's more difficult for Dim Son to pronounce so I am all for it :)

[bpilgrim]

12. Japanese: "Harbor Wave"

Tsunami (pronounced tsoo-nah-mee) is a Japanese word that can be translated as "harbor wave". A tsunami is a wave train (or series of waves) generated in water by an impulsive disturbance. Apart from impact of meteorites, other physical processes that can generate tsunami are earthquakes, landslides, volcanic eruptions, or even explosions. In other words, a tsunami can be generated by any disturbance that displaces a large water mass from its equilibrium position. Tsunami can savagely cover coastlines, causing devastating damages.

Tsunami differ from normal wind-generated waves (the waves everyone has observed on the beach) because of their longer periods and wave lengths. In fact, wind-generated waves usually have periods (time between two successive waves) of 5 to 20 seconds and a wavelength (distance between two successive waves) of 100 to 200 meters. A tsunami can have a period in the range of 10 minutes to 2 hours and a wavelength in excess of 500 km.

more...
http://www.spaceguarduk.com/cd/dict/dictionary/tsunami.htm

peace

[YDogg]

14. That is what I have learned ...

in the past week ... sad to say, I was generally uniformed about these phenomena.

I heard this morning about a "rogue wave" ... not sure how prevalant these are ...

[mrdmk]

18. A rogue wave (this is from my sufing days)

is a wave from a different direction and out of time with a normal wave pattern, also used to discribe a wave that is much larger than the average waves of the day. Thus never the less, it is a wind produced wave.

[SemperEadem]

19. I've experienced a rogue wave in California

the waves came lapping up on the shore, breaking a ways away from where I was standing.. all of a sudden, this big wave came up and next thing I knew, I was in water up past my knees... it had such a tow that I could feel it trying to pull me back out to sea. The next wave came up, but wasn't as huge as the one before it.. they became incrementally smaller as time passed. By that time, I was well up onto the sand.

[Canadian Socialist]

2. Because

tsunami is cooler sounding and harder for Bush* to say.

Yes, I know, inappropriate joke (lame though it is).

[donheld]

16. I see nothing inappropriate about it

Bush is an idiot. No reason to hide it.

Welcome to DU :hi:

[muriel_volestrangler]

8. Here's a true tidal wave

The River Severn has the world's second highest tidal range - up to 50 feet between low and high tides.

It also has one of the world's largest bores, caused because the river rapidly becomes narrower and shallower as the rising tide funnels water up from the Bristol Channel.

It forms below Awre, 15 miles south of Gloucester, then weaves round a giant horseshoe curve in the river and heads north, suddenly ending past the city at Maisemore Weir.

http://news.bbc.co.uk/2/hi/uk_news/1548455.stm

Being tidal, its times, and rough sizes, are predictable.

[MikeG]

9. No. 3 - The Larch - The Larch -The. Larch.

[Jesus H. Christ]

21. Another. Bay of Fundy.

Btw, is there a difference between a tidal wave and a tidal bore?

[SoCalDem]

13. It has nothing to do with tides.. It's an abnormal occurence

:)

[JVS]

15. WTF is tidal about it?

[Tinoire]

20. Tsunamis are unrelated to the tides although their impact depends on tides

Tsunamis are unrelated to the tides although their impact does depend on the tidal level.

Tsunamis are generated by seismic action on the sea bottom. Tidal waves are caused by tidal action alone, and have nothing to do with seismic activity.

It can get more technical than that but that's pretty much it in a nutshell.

[hfojvt]

22. it is funny how the intergenerational gap works

Some people answer the question as though there was never a time when people said "tidal wave" instead of tsunami. Of course, this was done without a major press release, so alot of older people still do not know that the terminology has changed.
Then again, just like older people do not know the new terminology, younger people are ignorant of the history of the term.
We also used to say things like Peking, Czechoslovakia, USSR, and Smokey the Bear. African countries have changed their names too, but I cannot remember the old ones anyway, so that is okay.