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Tsunami Facts for Kids - What causes a Tsunami - What is a Tsunami for Kids? - Tsunami Facts Tsunami

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Tsunamis are among the most devastating natural disasters on Earth. The human cost is staggering; since 1850, an estimated 420,000 people have been killed by the enormous waves. Tsunamis decimate the economy and ecology of the areas they strike; they have inflicted untold damage upon coastal property, communities and habitats. Tsunamis and the earthquakes that generate them have immediate aftereffects and long-term ramifications for the inundated areas.

Tsunami Origins

Most tsunamis originate at subduction zones, where a dense oceanic tectonic plate is sinking under lighter continental crust. As friction builds up between the two plates, they can become stuck. When the plates suddenly become unstuck or one of them fractures, energy is released as an earthquake. During a submarine earthquake, vertical motion of a plate displaces the water above it, generating waves that propagate across the ocean surface. Volcanic eruptions and submarine landslides also generate tsunamis. Because the earthquakes and volcanoes that produce them are difficult to predict accurately, tsunamis themselves are almost impossible to predict. When a tectonic disturbance happens, tsunami warnings can be issued, though tsunamis travel at such speeds -- 750 kilometers per hour on average -- that areas near the epicenter have little time to prepare.

Human Impact

The most terrible and immediate human aftermath of a tsunami is loss of life. Tsunamis claimed more 255,000 lives between 1900 and 2009, including the tsunami that originated off Sumatra on December 26, 2004, which killed more than 225,000 people. Tsunamis also destroy vast tracts of infrastructure and property. Loss of life and material is caused by the initial impact of the tsunami wave itself, followed by rapid receding of the water that carries people and debris with it.

Tsunamis continue to affect people after the waters have receded. Tsunamis can overwhelm sewage systems, destroy structures and leave decaying bodies in their wake, leading to long-term health problems related to contaminated water, exposure and increased spread of disease. Psychological damage can also linger; the World Health Organization found that Sri Lankan survivors of the 2004 tsunami suffered from post-traumatic stress disorder two years after the event.

Environmental Impact

Tsunamis can decimate ecosystems on land and in the sea. On land, animals are killed and plants uprooted. Inundation of salt water can promote inland invasion of salt-tolerant plants, such as grasses and mangroves, and loss of soil fertility in coastal farmland. Tsunamis also transport huge amounts of sand, creating fields of underwater dunes and reshaping beaches. The waves' power can tear up even rocky seabeds; after the tsunami that struck Japan March 11, 2011, Tohoku National Fisheries Research Institute found that large rocks had been overturned and pummeled along the coast, destroying whole communities of sea urchins and abalone, both vital fishery resources. Tsunamis also endanger the local environment through transportation of man-made waste, including building materials; spread of toxic substances, such as asbestos and oil; and release of radiation from damaged nuclear facilities.

Mitigation of Tsunami Aftermath

Proper disposal of waste is key during recovery. Improper burning or dumping of debris could cause secondary damage to people and the environment. During recovery, the top priorities are securing clean drinking water and food for affected people and containing hazardous material. Beyond immediate aid, the cost of reconstruction is a long-term burden. Infrastructure must be repaired before a region's economy can rebound. Private donations and aid from national and international organizations are crucial in the wake of a tsunami.

About the Author

Andrew McDonald is a vertebrate paleontologist and writer. He attained a Bachelor of Science in geology at the University of Nebraska-Lincoln and a PhD in vertebrate paleontology at the University of Pennsylvania. He studies the evolution of dinosaurs, primarily in the Cretaceous Period of western North America. McDonald writes articles for the "Space Reporter" and has named four new species of dinosaurs.

Photo Credits

Ken Ishii/Getty Images News/Getty Images

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Tsunamis are among the most devastating natural disasters on Earth. The human cost is staggering; since 1850, an estimated 420,000 people have been killed by the enormous waves. Tsunamis decimate the economy and ecology of the areas they strike; they have inflicted untold damage upon coastal property, communities and ...

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Inside the Eye of the Storm: The Cal OES/NOAA Tsunami Exercise

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By Campbell Phillips *

Here are the ten biggest tsunamis in recorded history, ranked by the devastation they wrought.

THE EARTHQUAKE AND subsequent tsunami that devastated Japan in 2011 showed just how vulnerable modern society is to the power of Mother Nature. While tsunamis were largely unknown to the wider public before the hugely destructive 2004 Boxing Day Tsunami, they have occurred many times in the past.

Tsunamis can be generated by any significant displacement of water in oceans or lakes, though are most commonly created by the movement of tectonic plates under the ocean floor, during an earthquake. But they can also be caused by volcanic eruptions, glacial carving, meteorite impacts or landslides.

Solids, Liquids And Gases - Science Series

Larger tsunamis don't alway cause the most destruction

Tsunamis have occurred often throughout history. So frequently in Japan, in fact, that they invented the word specifically for the phenomenon: ' tsu' meaning harbour and ' nami ' meaning wave.

"It's actually quite frightening to think that this [Japanese tsunami] event is smaller than the 2004 Indian Ocean tsunami, smaller even than the 1960 Chilean tsunami, yet the damage to Japan's people and economy is still profound," says Professor James Goff, co-director of the Australian Tsunami Research Centre and Natural Hazards Research Lab at the University of New South Wales. "It's a horrendous tragedy, caused by a completely unpredictable event."

Because little historical data exist on the size of tsunami waves, how many occur in one event, or how far they advance on shore, scientists rank them according to how much damage they wreak. However, assessing just how much damage a single tsunami event causes may take many months to years; and it may be some time before the Japan earthquake and tsunami can be truly rated on a historical scale.
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1. Sumatra, Indonesia - 26 December 2004

The 9.1 magnitude earthquake off the coast of Sumatra was estimated to occur at a depth of 30 km. The fault zone that caused the tsunami was roughly 1300 km long, vertically displacing the sea floor by several metres along that length. The ensuing tsunami was as tall as 50 m, reaching 5 km inland near Meubolah, Sumatra. This tsunami is also the most widely recorded, with nearly one thousand combined tide gauge and eyewitness measurements from around the world reporting a rise in wave height, including places in the US, the UK and Antarctica. An estimated US$10b of damages is attributed to the disaster, with around 230,000 people reported dead.

2. North Pacific Coast, Japan - 11 March 2011

A powerful tsunami travelling 800km per hour with 10m-high waves swept over the east coast of Japan, killing more than 18,000 people. The tsunami was spawned by an 9.0 magnitude earthquake that reached depths of 24.4km- making it the fourth-largest earthquake ever recorded. Approximately 452,000 people were relocated to shelters, and still remain displaced from their destroyed homes. The violent shaking resulted in a nuclear emergency, in which the Fukushima Daiichi nuclear power plant began leaking radioactive steam. The World Bank estimates that it could take Japan up to five years to financially overcome the $235 billion damages.

3. Lisbon, Portugal - 1 November 1755

A magnitude 8.5 earthquake caused a series of three huge waves to strike various towns along the west coast of Portugal and southern Spain, up to 30 m high, in some places. The tsunami affected waves as far away as Carlisle Bay, Barbados, where waves were said to rise by 1.5 m. The earthquake and ensuing tsunami killed 60,000 in the Portugal, Morocco and Spain.

4. Krakatau, Indonesia - 27 August 1883

This tsunami event is actually linked to the explosion of the Krakatau caldera volcano. Multiple waves as high as 37 m were propagated by the violent eruptions and demolished the towns of Anjer and Merak. The sea was reported to recede from the shore at Bombay, India and is said to have killed one person in Sri Lanka. This event killed around 40,000 people in total; however, as many as 2,000 deaths can be attributed directly to the volcanic eruptions, rather than the ensuing tsunami.

5. Enshunada Sea, Japan - 20 September 1498

An earthquake, estimated to have been at least magnitude 8.3, caused tsunami waves along the coasts of Kii, Mikawa, Surugu, Izu and Sagami. The waves were powerful enough to breach a spit, which had previously separated Lake Hamana from the sea. There were reports of homes flooding and being swept away throughout the region, with a total of at least 31,000 people killed.

6. Nankaido, Japan - 28 October 1707

A magnitude 8.4 earthquake caused sea waves as high as 25 m to hammer into the Pacific coasts of Kyushyu, Shikoku and Honshin. Osaka was also damaged. A total of nearly 30,000 buildings were damaged in the affected regions and about 30,000 people were killed. It was reported that roughly a dozen large waves were counted between 3 pm and 4 pm, some of them extending several kilometres inland at Kochi.

Atlas of Oceans Australian Geographic

7. Sanriku, Japan - 15 June 1896

This tsunami propagated after an estimated magnitude 7.6 earthquake occurred off the coast of Sanriku, Japan. The tsunami was reported at Shirahama to have reached a height of 38.2 m, causing damage to more than 11,000 homes and killing some 22,000 people. Reports have also been found that chronicle a corresponding tsunami hitting the east coast of China, killing around 4000 people and doing extensive damage to local crops.

8. Northern Chile - 13 August 1868

This tsunami event was caused by a series of two significant earthquakes, estimated at a magnitude of 8.5, off the coast of Arica, Peru (now Chile). The ensuing waves affected the entire Pacific Rim, with waves reported to be up to 21 m high, which lasted between two and three days. The Arica tsunami was registered by six tide gauges, as far off as Sydney, Australia. A total of 25,000 deaths and an estimated US$300 million in damages were caused by the tsunami and earthquakes combined along the Peru-Chile coast.

9. Ryuku Islands, Japan - 24 April 1771

A magnitude 7.4 earthquake is believed to have caused a tsunami that damaged a large number of islands in the region; however, the most serious damage was restricted to Ishigaki and Miyako Islands. It is commonly cited that the waves that struck Ishigaki Island was 85.4 m high, but it appears this is due to a confusion of the original Japanese measurements, and is more accurately estimated to have been around 11 to 15 m high. The tsunami destroyed a total of 3,137 homes, killing nearly 12,000 people in total.

10. Ise Bay, Japan - 18 January 1586

The earthquake that caused the Ise Bay tsunami is best estimated as being of magnitude 8.2. The waves rose to a height of 6m, causing damage to a number of towns. The town of Nagahama experienced an outbreak of fire as the earthquake first occurred, destroying half the city. It is reported that the nearby Lake Biwa surged over the town, leaving no trace except for the castle. The Ise Bay tsunamis caused more than 8000 deaths and a large amount damage.

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The 10 most destructive tsunamis in history

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By Campbell Phillips * Here are the ten biggest tsunamis in recorded history, ranked by the devastation they wrought. THE EARTHQUAKE AND subsequent tsunami that devastated Japan in 2011 showed just how vulnerable modern society is to the power of Mother Nature.

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Tsunami | The Dr. Binocs Show | Educational Videos For Kids

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Enjoy our awesome range of Earth facts for kids. Check out the cool trivia and have fun learning about some of our planet's most amazing features.

Tsunami Facts

Check out our tsunami facts for kids and learn some interesting information related to these great walls of water that can cause so much destruction. Find out what causes tsunamis and read about some notable recent examples of tsunamis that have occurred around the globe.

Tsunamis are huge waves of water that are usually caused by earthquakes or volcanic eruptions.

As a tsunami approaches the shore, water may recede from the coast, if it is shallow enough the water may be pulled back hundreds of metres. If you are in the area, observing this is a good indication that a tsunami is on the way.

Regions in tsunami danger zones often have warning systems in place to give people as much time to evacuate as possible.

When tsunamis hit shallow water (often near the coast) they slow down but increase in height.

An earthquake in the Indian Ocean off Indonesia in December 2004 caused a tsunami that killed over 200000 people in 14 countries. More earthquake facts.

In March 2011, the Tohoku earthquake off the eastern coast of Japan caused a tsunami that was a major factor in the death of over 15000 people.

The tsunami waves created by the Tohoku earthquake reached heights of over 40 metres (131 feet) in some areas, wiping out coastal towns and causing a number of nuclear accidents.

The Japanese word tsunami literally means 'harbor wave'.

Tsunamis are sometimes referred to as tidal waves but this term has fallen out of favour because tsunamis are not related to tides.

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Tsunami Facts for Kids - Interesting Information about Tsunamis

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Enjoy our awesome range of Earth facts for kids. Check out the cool trivia and have fun learning about some of our planet's most amazing features. Tsunami Facts Check out our tsunami facts for kids and learn some interesting information related to these great walls of water that can cause so much destruction.

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What is a Tsunami? Facts & Information - Geography for Kids | Educational Videos by Mocomi

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Educational Games, Worksheets, and More for Kids

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An Educational platform for parents and teachers of pre-k through 7th grade kids. Support your kids learning journey with games, worksheets and more that help children practice key skills. Download, print & watch your kids learn today!

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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.

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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.

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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!

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Tsunami facts: check out the mighty wave! - National Geographic Kids

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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! Meaning " great harbour wave" in Japanese, tsunamis are sometimes called "tidal waves" but their strength has nothing to do with the tides.

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Stephen Ornes lives in Nashville, Tenn., and his family has two rabbits, six chickens and a cat. He has written for Science News Explores since 2008 on topics including lightning, feral pigs, big bubbles and space junk.

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Earthquakes and landslides can create huge waves that travel across oceans.