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The world watched in horror as a tsunami caused devastation in Japan. A massive earthquake measuring 9.0 on the Richter scale hit the northeastern coastline triggering a 10m tsunami that caused extensive damage. It is the biggest recorded earthquake to hit Japan and tens of thousands of casualties are feared.
What are tsunamis?
Tsunamis are often called tidal waves. But these waves have nothing to do with the tides. They are usually caused by a submarine earthquake occurring less than 50 km below the sea floor, though they can also be caused by undersea volcanic eruptions or landslides.
Though on a potentially devastating scale, these are essentially giant ripples in the sea. The wavelength may be huge - 100 to 200 km, with a wave height of less than a metre, with an interval of between five minutes and an hour between waves. So a ship in the open ocean may not be at all bothered by it.
Tsunami heightens on approach to land
But as the waves approach land, friction slows them down, the wavelength shortens, and the height grows, to perhaps 15 to 30 m, especially in bays and inlets. The front of the first wave may be nearly vertical. There may be three to five major oscillations before the process stops. Tsunamis can be reflected and influenced by the shape of the sea floor, so their effects can vary greatly from place to place.
Sometimes, the first sign to reach land may be not the high wave that follows, but a trough, even exposing the sea floor. In November 1755 on All Saints Day, in Lisbon, Portugal, this happened, and as many curious onlookers rushed onto the floor of the bay to inspect this curious phenomenon, they were drowned by the tidal wave that followed just minutes later. And similar phenomena have been described in this latest disaster.
Previous tsunami disasters
The tsunami that hit south east Asia (11 countries) on December 26 2004 is estimated to have killed 250 000 people. The worst tsunami previously recorded, occurred in 1703 at Awa, Japan, killing 100 000 people. A tsunami in June 1896, hit the coast of Sanriku, Japan, killing and injuring over 30 000 people. The September 1923 major earthquake that struck Tokyo/Yokohama, killing over 134 000 people, also caused a tsunami which killed a further 60 people nearby. The 1960 earthquake on the coast of Chile, killed some 5 700, but also created tsunami-like seismic sea-waves which caused deaths and damage in Hawaii, Japan, and the Pacific coast of the United States.
While this recent event may represent the largest catastrophe affecting many different countries, one must remember catastrophes such as the July 1976 earthquake in T'ang-shan, China, east of Peking, which killed over 240,000 people.
The March 1964 Alaska earthquake was nearly as severe (8.5 Richter scale), but due to the low population density, only killed 131 people, though causing major property damage. It caused major re-shaping and tilting of the landmass in the area, and tsunamis caused extensive coastal damage, as far away as California.
The best organised region in the world, from the point of view of identifying, predicting and tracking such disasters, is that involving the Pacific Rim, with cooperation between Japan, Siberia, Alaska and Hawaii, with the SSWWS (Seismic Sea Wave Warning System) based in Honolulu, which coordinated data and issues warnings. This is the region most affected. Hawaii, for instance, has been struck by 40 tsunamis since 1819.
Related phenomena
A related phenomenon we haven't heard of this time, are called Seiches, which are oscillations of water in lakes or nearly landlocked bays, caused by tsunamis or earthquakes, and which may last for hours or even a couple of days. After the great Lisbon earthquake of 1755, oscillations were noticed in lakes and canals as far away as Scotland and Sweden. Similar vibrations were noticed in Texas around 40 minutes after the 1964 Alaska earthquake.
Another sinister possibility is sometimes called a seaquake, in which heavy waves from an earthquake are refracted through the seafloor, travelling at the speed of sound in water (around 1.5 km per second); which can strike a ship with such force as to give the impression that it has run into a solid object.
The story of the lost civilization of Atlantis is merely a legend, though many writers have insisted they have identified it, in America, Scandinavia, and the Canary Islands. The most credible identification would be with the major volcanic eruption on the island of Thera, in the Mediterranean, around 1500 B.C., which was accompanied by a series of earthquakes and tsunamis, which destroyed much of the civilisation of ancient Crete.
(Professor M.A. Simpson, Health24, updated March 2011)
(Pic: iStock. Graphic by Denzil Daniels, Health24)
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Your Comments
tsunamis
will it ever effect South Africa
will south africa effect by stunami.
No it will not affect south africa becouse we dont have submarines and volcanos.
NO,,,,,,
We have South America between us, however the economic damage this will do to the entire will be felt for years to come.
That was,,,,,
,,,,the entire world,,,
Tsunami
South Africa can not necessary be affected by Tsunami's for we are sitting in the african plate which rearely experience plate tactonic. However, we can feel the effect of the Tsunamis depending on where it came from
Tsunamis
Hey guys did you forget the Tsunami of 2004?
The North Coast of KZN was wrecked!
.
it is the time to start selling Life jackets
Our South African Tsunami
it's none other than julius...(shoot the boer, kill the farmer...nationalize mines) those are devastations waiting to happen & there's more to come in this beautiful country.
Tsunami In Japan
Its very disturbing to see incident of this nature. It makes me Noawa time in the Bible where people died in terrible way. My condolences to all those affected.
News24 misinformation
Please - check your facts before posting junk science like this.
Firstly - why the image of the perfectly blue wave. This is NOT what a tsunami looks like. Tsunamis are more akin to a temporary big increase in sea level.
Secondly, after correctly ascerting that Tidal Waves have nothing to do with tsunamis, you then include a plot with a legend the describes the wave front as " Tide edge" , and also continue to refer to tidal waves in your text?
This article is not the cause of good science.
Tsunami in SA
It is indeed possible in SA. There is a fault line in the South Atlantic, in line with Bouvet Island, that can cause just as much trauma as in Japan.
Eugene, I am not sure if you are a scientist or not...(I doubt). It can of course have a " blue wave" as indicated. It is just a matter of balance between potential & kinetic energy of the water. If the sea soffit incline steeply, the energy causes high waves.
I really hope it will not happen in MY time on earth, as I am on the beach front....
tshunamis
We can only pray for the countries hit by it. Please all the people pray for those who lost properties and love ones.
tsunamis
If we see what is happining arround the world in all these disasters,and the short duration between each of them we know two things for sure, Firstly, what the Bible says is true, (these things are to happen more frequently and greater in Intensity, like " birth pains" as we draw closer to the end), Mat 24v7. Secondly, We need to " Seek the LORD while he may be found call on Him while He is near. Let the wicked forsake their ways and the unrighteous their thoughts."
Repent & believe -Gospel
To @Gerrit
Gerrit,
The wavelength of tsunami are very long, and it is very rare of wave like this to form during tsunami events. Although I never claimed to be a scientist, I am a scientist, and work in tsunami research.
Although a tsunami can occur in SA, the South African coastline does enjoy some protection from an extensive continental shelf extending underwater, a protection the US West Coast and Japan does not enjoy.
Afraid
All i can say is we must realy hope and pray that it must not hit South africa. My heart goes realy out for those people who lost their loved one and properties how are they going to survives no nothing no where to begin....
Tsunami
Guys do you remember all this disaster movies, it seems like they are coming into reality, e.g. The movie 2012.
Tsunami
All i can say the end of the Earth is near. Just a pity that we dont know the date and time even though many people believe it will be in 2012 but if you are a christian you know thats bull. All my condolences to the Japanese people. God will help you over come this terrible time.
TSUNAMI
South Africans, let's pray so that Tsunami must not come to our country. God save Japanese people, AMEN.
Tsunami
Tsunami in South-Africa? Possible, what about the Milnerton fault that runs from Big Bay to False Bay?
Tsunami (SA)
Eugene, without trying to be nasty. The speed of the wave will be influenced by the depth of the ocean and will increas or decrease in height, depending on the depth of the ocean floor. Closer to shore the depth becomes steeply less and therefore the equal amount of kinetic energy will be carried over in height (potential energy) of the wave. If your'e a scientist and work with tsunamis, you then actually know this very good. This is school science !!
Help us God.
This is time that we should all pray for all people who are affected and who are still going to be affeced by what is happening now.I wish that God forgive us and not to punish us this way more especialy for the sake of young children who do not know where to go and who will endup not knowing who to resort to when they are left destitude.
Black Tsunami
We got hit by a black tsunami in 1994 and it has caused chaos, death and devastation ever since. If only the black tide would subside like the water...
no to africa
thera is no way a tsunami can hit us,God is punishing all those who understimate africans,look at the sept 11 atacks, i hope the dutch experience one.
Disturbed
It is disturbing indeed, but our mighty God Knows what tshunami victims are going through. Let us all support them in prayer.
terrible tsunami
all of this terrible things will come and go, but the end of the earth is not known yet. God please help those who trust you and protect the ones who lost thou path. i pray that Japan civilians be strong and trust God who will reconstract their Country
@mhlanga rb
o.o How racist can you get wishing something like that upon other people. Especially in the wake of the pure chaos hitting japan and the pain those who lost family and friends are going through.
Tsunami in Japan
Its very disturbing to see incident of this nature. It makes me think of Noawa's time in the Bible where people died in terrible way. My condolences to all those affected.
Survival
Survival after a tsunami might be possible depending how dispondent people are. What is even more disturbing are those nuclear power plants. To start using a race issue in comments on such issues is very immature such as the one made by mhlanga rb concerning dutch people. It must be that silly sangoma with his/her head in the clouds. All best wishes to the team being flown to Japan to assist.
Tsunami
We need to come together and pray for all these forces and people should be aware of God's presence.
Tsunami
I've been following news 24 for a while now and all these comments always end up in a racial debate. Clearly we claim to be the rainbow nation yet we still grey.
To the tsunami victims, stay strong and turn to the righteous path, for all of us let us be grateful for the perfect conditions we live in South africa minus the crime lol
God help them......
God help those who love and obey your words and those who trust in you. Africa its time 2 get together and pray for Japan. My heart and soul is with all the affected. God bless you all.
Tsunami
yes indeed God help those who love& obey ur words and those who trust in u.people of Japan Must put their faith in God almight cauze He knows everything and nothn is imposible to him.
naturally done
even if we can pray.... when nature calls no one can stand on its way, yes, we wish those people to recr soon but i undestand its hectic. keep on praying.
tsunami
people lets keep on praying ,to our Lord who can protect us.
Tsunami
Dear heavenly father please help the Japanese people to rebuild their lives as PAIN AND SUFFERING sees no race or colour we hold your holy name up HIGH and i ask for forgiveness of all our sins and our need to be materialistic thereby losing sight of what is really important, please show us you loving kindness and dish out 100 percent of your mercy in these difficult times. Father please calm the sea with your holy power thereby restoring our hope and faith in your POWER. Lord hear my prayer.
Tsunami
Dear heavenly father please help the Japanese people to rebuild their lives as PAIN AND SUFFERING sees no race or colour we hold your holy name up HIGH and i ask for forgiveness of all our sins and our need to be materialistic thereby losing sight of what is really important, please show us your loving kindness and dish out 100 percent of your mercy in these difficult times. Father please calm the sea with your holy power thereby restoring our hope and faith in your POWER. Lord hear my prayer.
Tsunami
Hits South Africa in Margate/Uvong in Kwa-zulu Natal a few years ago, dont know what causes it but yes it can happen
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