# data[].attributes.attachment_link.readable_text
Tsunamis, often referred to as tidal waves, are a series of ocean waves, called a wave train, caused when an earthquake or other major disturbances like landslides and volcanic eruptions displace hundreds of cubic kilometers of water from its equilibrium position. Pronounced tsoo-nah-mee, Tsunami is a Japanese word that translates into "harbor wave". Tsunamis can travel across the ocean at up to 805 kilometers an hour.

A tsunami is different from a normal wind-generated wave because of its longer periods and wave lengths. Though used interchangeably, tsunami and tidal wave are not synonymous. This is so because tsunamis have nothing to do with tides.
What causes Tsunamis?
Undersea earthquakes at tectonic plate boundaries, underwater landslides or volcanic eruptions and asteroid impact are some of the factors that cause Tsunamis.

It has bee estimated that earthquakes are responsible for the creations of more than 80% of tsunami in the Pacific Ocean. There is every possibility that landslides can cause tsunami. These undersea landslides are triggered by earthquakes resulting in the displacement of water and increase in the height of Tsunami. Though less common, volcanic eruptions are also responsible for the creation of tsunami. Though rare, the impact of a large asteroid plunging into an ocean may also launch tsunami.
Where do tsunamis occur most often?
Tsunamis can occur in any major body of water. However, they are most common in the Pacific Ocean where tsunamis occur most often. Some 80 percent of tsunamis take place within the Pacific Ocean's "Ring of Fire". The reason is not far to seek. Pacific Ocean zone is home to volcanoes and underwater earthquakes. Japan, the United States and Chile are some of the countries which have long coastlines on the Pacific Ocean. Needless to say, these countries run the risk of being hit by a tsunami. However, tsunamis can strike any part of the world. In 2004 a massive earthquake in the Indian Ocean triggered a destructive tsunami that played havoc with the human lives killing over 230,000 people.
Why are tsunamis dangerous?
In deep water, a tsunami moves at great speeds. However, when it approaches shallow water near coastal areas, the tsunami slows down but increases in height sometimes reaching heights of over 30 meters. It can still be moving travelling at a speed of over 50 miles per hour. A gigantic wall of water traveling at such speed can apparently result in widespread damage to the entire population and properties of the coastal cities because .a huge tsunami has the potential of travelling several miles inland.

Tsunami Warnings
Although predicting a tsunami is impossible, once one is generated, it is possible to forecast when a wave will hit land by the use of early detection systems and measurement technologies that are in place in the coastal regions. Subsequently, people are asked to leave the area adjacent to the coast.

It is in the essential fitness of things that people living in the areas near the coasts will do well to remember that the passing of the first wave does not guarantee them safety unless it is officially declared that it is safe to return to the locations that are at the risk of being hit by tsunami.`

Tsunami Questions & Answers:

Question 1: What was the largest Tsunami ever recorded?

Answer 1: The largest ever Tsunami ever recorded was in Alaska in 1958 in Lituya Bay.

Question 2: Where do Tsunamis happen?

Answer 2: A Tsunami can occur in any ocean, however some area's of the world are more prone to Tsunamis than others. In recent years Asia has been hit particularly bad by large Tsunamis caused by massive earthquakes in the region. The Japan Tsunami in 2011 and the 2004 Tsunami that hit Thailand, Indonesia, Sri Lanka and other regions caused devastating damage and thousands of deaths.

How fast can a Tsunami travel in the ocean?

Answer 3: A Tsunami can travel at speeds at over 500 mph, as the Tsunami approaches land it will slow down to speeds of around 30 mph or a little less.

Answer 4: A person who studies Tsunamis is called a Seismologist. They also study earthquakes.

Question 5: Can a Tsunami be detected to give early warnings?

Answer 5: Yes Tsunamis can be detected through the Tsunami warnings centers that are based around the world. They detect seismic movement in the oceans. Once an earthquake has registered the centers will monitor the waters levels in the ocean. If they feel a Tsunami warning should be issued they will do so giving vital time for people living in coastal regions to take precaution and find higher ground or move inland.

How can I stay safe in the event of a Tsunami?

Answer 6: Firstly stick with Mom and Dad. Listen to local TV and radio reports. If an evacuation order is issued leave straight away for higher ground or go as far inland as possible. Do not waste time gathering belongings like your iPad, Laptop, your life is more important. Have a family escape plan prepared and practice. Have a portable medical and supplies kit on the ready in case you need to spend some time on high ground. Have a look at this valuable website: http://www.nws.noaa.gov/om/tsunami/

# data[].attributes.attachment_link.description
Tsunamis, often referred to as tidal waves, are a series of ocean waves, called a wave train, caused when an earthquake or other major disturbances like landslides and volcanic eruptions displace hundreds of cubic kilometers of water from its equilibrium position. Pronounced tsoo-nah-mee, Tsunami is a Japanese word that translates into "harbor wave".

# data[].attributes.attachment_link.readable_text
A tsunami is a natural disaster which is a series of fast-moving waves in the ocean caused by powerful earthquakes, volcanic eruptions, landslides, or simply an asteroid or a meteor crash inside the ocean. A tsunami has a very long wavelength. It can be hundreds of kilometers long. Usually, a tsunami starts suddenly. The waves travel at a great speed across an ocean with little energy loss. They can remove sand from beaches, destroy trees, toss and drag vehicles, houses and even destroy whole towns. Tsunamis can even be caused when a meteorite strikes the earth's surface, though it is very rare. A tsunami normally occurs in the Pacific Ocean, especially in what is called the ring of fire, but can occur in any large body of water.

The water often draws back from the seacoast half of the wave period prior to the wave getting to the coast. If the slope of the coast is not steep, the water may pull back for hundreds of meters. People who do not know of the danger often remain at the shore.

Tsunamis cannot be prevented. However, there are ways to help stop people dying from a tsunami. International and regional warning systems, especially for the Pacific Ocean, issue alerts before the big waves reach the shore. Because the earthquake that caused the tsunami can be felt before the wave gets to the shore, people can be warned to go somewhere safe.

Tsunamis are often called tidal waves because they usually rise and fall more slowly than ordinary ocean surface waves. This name is misleading, because tsunamis are not related to tides; they merely rise slowly as a series of fast-moving waves in the ocean caused by powerful earthquakes or volcanic eruptions.

The deadliest tsunami recorded in documented history was on 26 December 2004, and is known as the 2004 Indian Ocean Tsunami. It was caused by an earthquake. The earthquake was said to have a magnitude of 9.3 on the Moment magnitude scale. It was centered in the ocean near the coast of Sumatra, Indonesia. Over 215,000 people, mainly on the shores of the Indian Ocean, died from this disaster. The giant wave moved very quickly. Thousands of people in Indonesia, Sri Lanka, Thailand, India, Somalia, and other nations, were killed or injured by it.

Yet, the most expensive tsunami ever was the 2011 Tōhoku earthquake and tsunami. It is said to have cost the Japanese government around $150 billion, which is equivalent to about 12 trillion yen. It went a huge distance in inland, and is also the 4th largest tsunami in history.

There is another type of tsunami known as a megatsunami, which is mainly due to external impact on the ocean, like an asteroid or meteor crash, a landslide, a rockslide etc.

While Japan may have the longest recorded history of tsunamis, the sheer destruction caused by the 2004 Indian Ocean earthquake and tsunami event mark it as the most devastating of its kind in modern times, killing around 230,000 people. The Sumatran region is also accustomed to tsunamis, with earthquakes of varying magnitudes regularly occurring off the coast of the island.

Of historical and current importance are the 1755 Lisbon earthquake and tsunami (which was caused by the Azores-Gibraltar Transform Fault), the 1783 Calabrian earthquakes, each causing several tens of thousands of deaths and the 1908 Messina earthquake and tsunami. The tsunami claimed more than 123,000 lives in Sicily and Calabria and is among the most deadly natural disasters in modern Europe. The Storegga Slide in the Norwegian Sea and some examples of tsunamis affecting the British Isles refer to landslide and meteotsunamis predominantly and less to earthquake-induced waves.

As early as 426 BC the Greek historian Thucydides inquired in his book History of the Peloponnesian War about the causes of tsunami, and was the first to argue that ocean earthquakes must be the cause.

The Roman historian Ammianus Marcellinus ( Res Gestae 26.10.15-19) described the typical sequence of a tsunami, including an earthquake, the sudden retreat of the sea and a following gigantic wave, after the 365 AD tsunami devastated Alexandria.

The principal generation mechanism of a tsunami is the displacement of a substantial volume of water. This displacement of water is usually attributed to either earthquakes, landslides, volcanic eruptions, glacier calvings or more rarely by meteorites and nuclear tests.

Earthquakes

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 crust deforming; when these earthquakes occur beneath the sea, the water above the deformed area is displaced. Movement on normal faults can also cause displacement of the seabed, but only the largest of such events cause enough displacement to cause a significant tsunami, such as the 1977 Sumba and 1933 Sanriku events.

Tsunamis have a small wave height offshore, and a very long wavelength (often hundreds of kilometres long, whereas normal ocean waves have a wavelength of only 30 or 40 metres), which is why they generally pass unnoticed at sea, forming only a slight swell usually about 300 millimetres (12 in) above the normal sea surface. They grow in height when they reach shallower water. A tsunami can occur in any tidal state and even at low tide can still inundate coastal areas.

Landslides

In the 1950s, it was discovered that tsunamis larger than had previously been believed possible can be caused by giant submarine landslides.

These rapidly displace large water volumes, as energy transfers to the water at a rate faster than the water can absorb.

Scientists named these waves megatsunamis.

Meteorological

Some meteorological conditions, especially rapid changes in barometric pressure, as seen with the passing of a front, can displace bodies of water enough to cause trains of waves with wavelengths like seismic tsunamis, but usually with lower energies.

Man-made or triggered tsunamis

There have been studies and one actual attempt to create tsunami waves as a tectonic weapon.

In World War II, the New Zealand Military Forces initiated Project Seal, which attempted to create small tsunamis with explosives in the area of today's Shakespear Regional Park; the attempt failed.

Tsunamis are made by permanent large vertical displacements of very large volumes of water which do not occur in explosions.

Surviving tsunamis

Tsunamis are very strong and can go many kilometers inland. Around 5 to 10 minutes before a tsunami hits, the sea seems to go back by an unusual distance. This is a warning that a tsunami can occur.

The best way to evacuate is to climb to an elevated area. If a person notices strange or unusual behavior in animals, he/she can also take that as a warning and go inland. However, if it still looks like the wave can absorb the person, the most suitable alternative will be to hold on to something sturdy, like a tree, so he/she does not totally get carried away and injured.

Other Pages

Images for kids

In Spanish: Tsunami para niños

# data[].attributes.attachment_link.readable_text
Have you ever heard about a tsunami or seen something on TV about them?

Well, they are a mighty force to be dealt with, and they can be deadly.

Here we take a look at everything you need to know about these enormous walls of water so you can be the cool expert on tsunamis in your next test.

Tsunami Facts for Kids

Tsunami is a Japanese word and translated into English means, "harbor wave."

Tsunamis are sometimes called tidal waves

They are huge waves of water caused by a volcanic eruption or earthquakes

Japan has the highest number of recorded tsunamis

Areas within a tsunami danger zones have warning systems to monitor potential danger

The warning system in the Pacific Ocean is called the DART system which stands for Deep-ocean Assessment and Reporting of Tsunamis!

The first wave of a tsunami might not be the biggest. There may be bigger and stronger ones to follow.

What are tsunamis?

They are massive, crashing waves that head towards the shore.

As they do so, they keep growing in size and get bigger and bigger along the way.

It must be frightening to see that coming your way.

As we said, they can cause heaps of harm as they charge onto land, flood cities, and destroy homes.

They are not just one big massive wave, but a whole series of waves called a 'wave train.'

What causes a Tsunami?

Tsunamis are caused by a significant shift in water.

Have you ever moved forward in the bath quite fast?
Well, what happens?
It causes a pretty big wave.

Bet your Mum's not happy when she sees the mess!

It's the same type of thing in the ocean.

When a large amount of water is moved suddenly, a massive wave is formed.

They can be caused by a movement that comes from earthquakes, landslides, volcanic eruptions, glaciers breaking off as well as meteorites.

These all create a lot of movement.

Most tsunamis however are caused by earthquakes. When there's an earthquake a large area of the Earth's crust moves suddenly.

When this happens underwater, you get big gaps that can appear on the ocean floor. Water then rushes in to fill the gap, and a tsunami is on its way to forming.

What happens during a Tsunami?

Once the water is moved by an earthquake or something else, large waves like ripples spread out from where the water was first moved from.

These waves can move quickly and for seriously long distances. Some tsunamis have traveled for thousands of kilometers across the ocean.

They can even travel at speeds of up to 804km per hour! No way, no wonder they cause so much destruction. That is pretty much the same speed as a jumbo jet!

As the waves travel through the deep parts of the ocean, the top of them is quite short.

This makes it difficult to see if a tsunami is coming as you might not be able to see them in the deep ocean.

But, the closer they come to land and shallow waters, those waves certainly get humongous, all piling up on top of each other.

Sometimes tsunamis like to trick us. As they reach the coastline, a trough of the wave can be seen.

What this does is causes the water to move back down the shoreline, and it can be quite some distance.

The reason this is not cool, is that people think it's disappearing and head out into the open area.

As the waves arrive on the shore they are a very tall wall of water.

They rush inland at huge speeds and with a great deal of muscle behind them.
They can rush inland for long distances. S

ome tsunamis have been known to reach heights of nearly 31m. That certainly would have you shaking at just the site of it!

Sometimes, just when you think it's over, more waves may arrive. This can be anything up to a couple of minutes.

Where do Tsunamis Happen?

Tsunamis can happen in any significant body of water but are most common in the Pacific Ocean, where there are loads of underwater earthquakes and volcanoes.

Countries with long coastlines on the Pacific Ocean, such as Japan, Chile, and the United States, are all at risk of being hit by a tsunami.

But, they can happen anywhere!

In 2004 a massive earthquake in the Indian Ocean caused a destructive tsunami, which killed over 230,000 people. That is frightening!

Warnings

Many coastal areas have tsunami warning systems.

If they know an earthquake has happened that might cause a tsunami, people are issued warnings to leave the area or find higher ground. Lucky for that!

So, there you have it, everything you need to know about tsunamis.

Hope you enjoyed our interesting facts and they can help you out with your schoolwork.

# data[].attributes.attachment_link.description
Have you ever heard about a tsunami or seen something on TV about them? Well, they are a mighty force to be dealt with, and they can be deadly. Here we take a look at everything you need to know about these enormous walls of water so you can be the cool expert on tsunamis ...

# data[].attributes.attachment_link.readable_text
They can speed across the ocean as fast as a jet plane, swallow up islands and wipe out villages.

But what causes tsuamis...? Join National Geographic Kids and dive into our tsunami facts to find out!

What causes a tsunami?

Meaning " great harbour wave" in Japanese, tsunamis are sometimes called "tidal waves" but their strength has nothing to do with the tides. About four out of five tsunamis happen within the Ring Of Fire, a zone in the Pacific Ocean where earthquakes and volcanic eruptions frequently take place.

Giant slabs of the Earth's crust, called tectonic plates, grind together. Sometimes, though, the plates get stuck, the pressure builds up and they suddenly slam into a new position. This causes an earthquake. If an earthquake lifts or drops part of the ocean floor, the water above rises and starts spreading across the ocean, causing a tsunami. Underwater landslides or volcanic eruptions can also displace water (cause water to spread across the ocean) and may lead to a tsunami.

How big is a tsunami?

Out in the open ocean, tsunami waves are only about one-metre high because the water is deep. However, as the water becomes shallow, the waves slow down and begin to grow. They can rise 35m or higher - that's the same as a 10-floor block of flats! However, the scariest thing about a tsunami is its wavelength, as this determines how far inland it can travel. Whereas a large wave caused by a storm might have a wavelength of up to 150m, a tsunami could reach up to a fearsome 1,000km!

How fast is a tsunami?

A normal wind wave travels at about 90kmh, but a tsunami can race across the ocean at an incredible 970kmh! Sometimes, before a tsunami hits, there is a huge vacuum effect, sucking water from harbours and beaches. People can see the ocean floor littered with flopping fish and other sea animals. Then a wave blasts onto the shore minutes later, then another and another for two hours or more. There may also be up to one hour between each wave.

Can you predict when a tsunami is coming?

To save lives, scientists established the Pacific Tsunami Warning System, based in Hawaii, in the USA. Its network of detectors can track quakes that may cause a tsunami. These waves can race from one side of the Pacific Ocean to the other in less than a day, so people need to be warned in time to head for higher ground!

What do you think of these tsunami facts? Let us know by leaving a comment, below!

# data[].attributes.attachment_link.title
Tsunami facts: check out the mighty wave! - National Geographic Kids

# data[].attributes.attachment_link.description
Check out these epic tsunami facts from National Geographic Kids! How do tsunamis form? And how big are they? Find out all about them in our tsunami facts...

# data[].attributes.attachment_link.readable_text
What is a tsunami?
A tsunami is a large ocean wave usually caused by an underwater earthquake or a volcanic explosion. Tsunamis are NOT tidal waves. Tidal waves are caused by the forces of the moon, sun, and planets upon the tides, as well as the wind as it moves over the water. With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunamis cause so much damage!

How are tsunamis generated?
Tsunamis are generated by any large, impulsive displacement of the sea level. The most common cause of a tsunami is sea floor uplift associated with an earthquake. Tsunamis are also triggered by landslides into or under the water surface, and can be generated by volcanic activity and meteorite impacts.

How often do tsunamis occur?
On the average, two tsunamis occur per year throughout the world which inflict damage near the source. Approximately every 15 years a destructive, ocean-wide tsunami occurs.

Can strike-slip (horizontal motion) earthquakes trigger tsunamis?
Yes, approximately 10-15% of damaging tsunamis are triggered by strike-slip earthquakes. This type of earthquake is less likely to trigger a tsunami than one with vertical motion. The waves are likely generated by associated landslides or motion of a sloping bathymetric feature. Tsunamis generated by strike-slip earthquakes normally affect regions near the source only.

What does the word "tsunami" mean?
Tsunami (soo-NAH-mee) is a Japanese word meaning harbor wave.

How fast do tsunamis travel?
Tsunami velocity depends on the depth of water through which it travels. Velocity equals the square root of the product of the water depth times the acceleration of gravity. Tsunamis travel approximately 475 mph in 15,000 feet of water. In 100 feet of water the velocity drops to about 40 mph.

Did you know...A tsunami travels from the central Aleutian Islands to Hawaii in about 5 hours and to California in about 6 hours, or from the Portugal coast to North Carolina in about 8.5 hours.

How big is a tsunami?
Tsunamis range in size from inches to over a hundred feet. In deep water (greater than 600 feet), tsunamis are rarely over 3 feet and are not normally noticed by ships due to their long period or time between crests. As tsunamis propagate into shallow water, the wave height can increase by over 10 times. Tsunami heights vary greatly along a coast. The waves can be amplified by shoreline and sea floor features. A large tsunami can flood low-lying coastal land over a mile from the coast.

What does a tsunami look like when it reaches shore?
Normally, a tsunami appears as a rapidly advancing or receding tide. In some cases, a wall of water or series of breaking waves may form.

How is a tsunami different from a wind-generated wave?
Wind-generated waves usually have periods or time between crests between 5 and 15 seconds. Tsunami periods normally range from 5 to 60 minutes. Also, wind-generated waves break as they shoal and lose energy offshore. Tsunamis act more like a flooding wave. A twenty foot tsunami is a twenty foot rise in sea level.

What are nature's signs that a tsunami may be imminent?
There are a few signs like hard ground shaking for 20+ seconds near the coast or a sudden sea level withdrawal. Tsunamis may be accompanied by loud, booming noises.

Can earthquakes and tsunamis be predicted?
No, earthquakes cannot be predicted. Once an earthquake has occurred, the arrival time of a tsunami, if generated, can be determined accurately. There is not normally enough time to accurately predict tsunami heights near the source. Away from the source, tsunami wave heights can be estimated based on mathematical tsunami models and observed wave heights.

Aerial video of the tsunami that devastated Japan on March 11, 2011.

Click Here to see an animation of an earthquake and the resulting tsunami. It's great for kids, because they get to see how it actually happens!
What are some of the most damaging tsunamis?

Japan: Major tsunami in 2011 generated in the Pacific Ocean.

Asia: Asian tsunami in 2004 generated in the Indian Ocean.

Alaska: Major tsunamis were generated along the Alaskan coast in 1946, 1957, 1958, 1964, and 1965. Many other locally generated tsunamis occurred prior to those dates.

US/Canada West Coast: Tsunamis were generated locally in 1812, 1873, 1878, 1927, 1930, 1946 and 1949. The west coast was also impacted by tsunamis generated in other regions in 1877, 1946, 1952, 1957, 1960, 1964, 1975, 2006, and 2010.

US/Canada Atlantic Coast: Tsunamis were recorded in 1755, 1884, 1886, and 1929.

Puerto Rico and the Virgin Islands experienced damaging tsunamis in 1867 and 1918.

Click Here for the NOAA/National Geophysical Data Center tsunami catalog.

TSUNAMI WARNING- A tsunami warning indicates that a tsunami may be imminent and that coastal locations in the warned area should prepare for flooding. The initial warning is typically based solely on seismic information. After the tsunami is recorded on sea level gages, the warning will be cancelled, restricted, expanded, or downgraded to an advisory. Warnings indicate that flooding up to the maximum expected limit is possible and residents should follow their local emergency management instructions. Warnings are issued when the earthquake information or tsunami forecasts indicate that a wave over 1 meter in amplitude is expected, possible, or ongoing.

TSUNAMI ADVISORY- A tsunami advisory indicates a tsunami which may produce strong currents and is dangerous to those in or very near the water is expected. Large inundations are not expected in areas under advisory status. Advisories will be cancelled, extended, or upgraded to a warning depending on the event severity. Advisories are issued when the tsunami forecast is in the range of 0.3 to 1 meter, or an observed tsunami is in the range of 0.5 to 1.0 meters.

TSUNAMI WATCH- A tsunami watch is an early alert issued to areas which may later be impacted by a tsunami. Tsunami impact is normally at least three hours away for regions within a tsunami watch. The watch will either be upgraded to a warning or advisory in subsequent messages or cancelled depending on the severity of the tsunami. People within a watch area should stay alert for further information regarding tsunami threat.

CREST - The top of a wave.

FJORD - A narrow sea inlet between cliffs or steep slopes.

SURGE - A large wave or billow.

TROUGH - The lowest point between waves.

Click Here to get the latest tsunami warning information from the NWS.

PLAN FOR A TSUNAMI: Have a disaster plan. Know whether you're at risk for danger. Plan an evacuation route. Prepare a disaster supplies kit for your home and car. Include a first aid kit, canned food and a can opener, bottled water, battery-operated radio, flashlight, protective clothing and written instructions on how to turn off electricity, gas, and water.

DURING A TSUNAMI: Follow the instructions issued by local authorities. You will probably want to evacuate immediately. Get to higher ground and as far inland as you can.

AFTER A TSUNAMI: Help injured or trapped people. Stay out of a building if water remains around it. Tsunami waters can cause buildings to sink, floors to crack, or walls to collapse. When re-entering homes, use extreme caution. Check for gas leaks. Open windows and doors to help dry things out. Look for fire hazards.

Lesson Plan: Here is a great lesson plan on learning about tsunamis. Note: This is a PDF file, so you need to have Adobe Acrobat Reader.

Lesson Plan: Here is a great lesson plan on tracking a tsunami.

Lesson Plan: Here is a great lesson plan on tsunamis and how they devastating effects they may cause in the world.

# data[].attributes.attachment_link.description
What is a tsunami? A tsunami is a large ocean wave usually caused by an underwater earthquake or a volcanic explosion. Tsunamis are NOT tidal waves. Tidal waves are caused by the forces of the moon, sun, and planets upon the tides, as well as the wind as it moves over the water.

# data[].attributes.attachment_link.description
Kids learn about tsunamis including what causes them such as earthquakes, where they occur, why they are dangerous, and what happens during a tsunami event.