49 Fun Facts About Tsunami

What does the Japanese word 'tsunami' literally mean?

Harbour wave joins tsu (harbour) and nami (wave). English adopted the word in 1896, after a tsunami devastated Japan's Sanriku coast.

What fundamentally causes a tsunami?

The displacement of a large volume of water is all it takes, so a landslide can raise a tsunami in a lake just as an undersea earthquake can in an ocean.

Which popular name for a tsunami do scientists avoid because the Moon and Sun play no part in causing one?

Tidal wave suits the look of one, since a tsunami rushes ashore like a fast-rising tide and not a breaking wave, but real tides come from the pull of the Moon and Sun.

Which Athenian historian argued that earthquakes cause tsunamis?

Thucydides was describing 426 BC, when the same run of earthquakes that flooded Greek coastal towns also made a Peloponnesian army abandon its invasion of Attica.

In 479 BC, a tsunami drowned soldiers of which power as they besieged the Greek town of Potidaea?

Persia's soldiers set out across the seabed at an unusually low ebb, and Herodotus says the returning flood drowned those who could not swim.

An earthquake near Crete in 365 AD sent a tsunami that flung ships onto rooftops in which great port city?

Alexandria's stranded ships were recorded by the Roman historian Ammianus Marcellinus, who also saw a vessel rotting nearly two miles inland in Greece.

Which Pacific island nation's undersea volcano exploded in January 2022, sending tsunami waves across the ocean?

Tonga's Hunga Tonga-Hunga Ha'apai eruption wiped away the young island that had risen in 2015 and joined two older ones.

About four in five of the world's tsunamis strike around which zone?

Ring of Fire volcanoes and faults rim the Pacific, where ocean plates dive beneath their neighbours. Those subduction zones produce the giant undersea earthquakes behind most tsunamis.

A tsunami crosses the deep ocean about as fast as which of these?

A jet airliner cruises at roughly the same 800 km/h. Near land the wave slows to the speed of a car and grows in height instead.

Roughly how tall is a tsunami in the deep ocean?

About 1 metre is as tall as a tsunami usually gets in the deep ocean, so ships cannot feel one pass beneath them. It rears up only when it reaches shallow water.

The Great Wave off Kanagawa, a print often taken to show a tsunami, is by which Japanese artist?

Hokusai more likely drew a storm wave than a tsunami: researchers who sized it against the boats it threatens put it at about 10 metres tall, breaking out in the bay.

Which process slows a tsunami and makes it taller near shore?

Wave shoaling, named for a shoal, a shallow stretch of water, compresses a tsunami as the shallows slow it down, so its waves bunch together and grow in height.

What do scientists call the vertical distance a tsunami climbs up the land above sea level?

Run-up is read after the wave has gone, from the highest line of debris and stripped vegetation that the water left on the land.

Why does the sea often pull far back just before a tsunami strikes?

The wave's trough arrives first in many tsunamis, sucking water seaward and baring the seabed minutes before the crest floods in, so a vanishing sea is a signal to run for high ground.

What do scientists call the series of waves that makes up a tsunami?

A wave train can keep arriving for hours, and the first wave may not be the biggest, which is why people are told to stay away from the shore long after it hits.

In 1958 a wave surged 524 metres up a mountainside beside a remote bay in which US state?

Alaska's Lituya Bay wave stripped the forest from the slope, yet Howard Ulrich and his seven-year-old son, anchored in the bay in a fishing boat, rode over it and lived.

What set off the giant 1958 wave in Lituya Bay?

An earthquake shook a huge rockslide into the bay: about 30 million cubic metres of rock fell some 900 metres into the water, and the splash tore the forest off the facing slope.

In 1963 a landslide from Monte Toc sent a wave over the Vajont Dam, killing about 2,000 people in which country?

Italy's Vajont Dam, then among the tallest in the world, was left almost intact: the wave leapt over it and wiped out the town of Longarone in the valley below.

Which Canary Islands volcano, which erupted in 2021, is at the centre of a disputed Atlantic megatsunami theory?

Cumbre Vieja's flank, a 2001 paper warned, could collapse and send giant waves to the Americas, but later research found it would crumble piece by piece and raise waves there no higher than a common storm surge.

A tsunami around 1600 BC from which volcano is often blamed for the decline of Minoan civilisation?

Santorini's eruption buried the Minoan town of Akrotiri in ash and sent waves onto Crete, though whether that really brought down the Minoans is still debated.

The 2018 collapse of which volcano killed more than 400 people with a tsunami that arrived without warning?

Anak Krakatoa, 'child of Krakatoa', had grown in the crater left by the 1883 eruption. The 2018 landslide that raised the wave cut the island's height from 338 metres to about 110.

What is a tsunami called when it cannot be linked to any known earthquake?

Orphan fits a wave that struck Japan in January 1700 with no earthquake felt there. Its parent was later traced to a giant quake off North America's Pacific Northwest.

The accidental 1917 explosion of a munitions ship triggered a tsunami in which North American harbour?

Halifax, Nova Scotia, lost nearly 2,000 people when the ship blew up after a collision in the harbour, one of the largest human-made explosions before the atomic bomb.

Which country's military tested a 'tsunami bomb' off its own coast in World War II's Project Seal?

New Zealand's military set off test blasts in the sea near Auckland to see whether explosives could raise a destructive wave, but the bomb was never tried at full scale.

An underwater bomb test at which Pacific atoll in 1946 showed that nuclear blasts make poor tsunami weapons?

Bikini Atoll's Baker shot, the first underwater test of an atomic bomb, threw up a vast column of spray, yet the waves reaching the nearest island a few kilometres away were only a few metres high.

British and Commonwealth media named the 2004 Indian Ocean tsunami after which holiday?

Boxing Day, 26 December, brought no alert because the Indian Ocean had no tsunami warning system, so nearly all the victims were taken by surprise, some of them hours after the earthquake.

Roughly how many people were killed by the 2004 Indian Ocean tsunami?

About 230,000 people died or went missing, the most in any tsunami on record, and the toll spurred the ocean's governments to start building a warning system within months.

Off which Indonesian province was the epicentre of the 2004 earthquake?

Aceh had been at war with Indonesia's government for almost 30 years. The disaster pushed both sides into a peace deal, signed eight months later, that cites the tsunami.

NASA calculated that the 2004 Indian Ocean earthquake shifted enough rock to speed up what, very slightly?

The Earth's rotation quickened as mass moved closer to the planet's axis, like a skater pulling in her arms, shortening each day by about three millionths of a second.

Where had ten-year-old Tilly Smith learned the tsunami warning signs she recognised on a Thai beach in 2004?

In a school geography lesson two weeks earlier, her teacher Andrew Kearney had shown a film of an earlier tsunami. After her family raised the alarm, no one was killed on that beach.

The 2004 tsunami crossed the ocean for seven hours and still killed people on which continent, 5,000 km from the earthquake?

Africa's Somali coast lost nearly 300 people. The fault ran north to south, so the waves were strongest to the east and west, and distance alone was no protection.

Which animals in Sri Lanka were reported moving inland before the 2004 wave, possibly having heard it coming?

Elephants at Yala National Park were seen running from the beach about an hour before the waves, though scientists remain unconvinced that animals can sense a tsunami coming.

Japan's 2011 tsunami was filmed from a helicopter as it flooded the runways of which city's airport?

Sendai, the nearest big city to the epicentre, sits on a flat coastal plain, which let the water run several kilometres inland and across the airport.

A Harley-Davidson swept away by Japan's 2011 tsunami washed up a year later on a beach in which country?

Canada's Haida Gwaii islands are where the bike came ashore, still inside its storage container. Harley-Davidson staff in Japan then traced the owner, who had lost his home and three relatives.

At Fukushima Daiichi, the tsunami caused three meltdowns by flooding what?

Backup diesel generators sat in basements at a plant planned for waves of about 6 metres. The tsunami was more than twice that height, and without power the reactors could not be cooled.

Waves from Japan's 2011 tsunami crossed 13,000 km of ocean and broke city-sized icebergs off which landmass?

Antarctica's Sulzberger Ice Shelf lost an iceberg about the size of Manhattan, even though the swell that reached it was only about 30 centimetres high.

In 1946 an Aleutian Islands earthquake sent a deadly tsunami into which town on Hawaii's Big Island?

Hilo bore the worst of a wave that crossed the Pacific in about five hours. No warning reached Hawaii, so the islands were caught off guard when it struck.

Where is the Pacific Tsunami Warning System based?

Honolulu, Hawaii, has housed the service since the late 1940s. It was set up after a 1946 tsunami from a distant earthquake struck the islands with no warning.

NOAA's DART buoys detect a passing tsunami using what, anchored on the ocean floor beneath them?

Bottom pressure sensors feel the extra weight of water as a tsunami passes overhead and send the reading by sound to the buoy, which relays it by satellite to the warning centres.

In the US tsunami alert system, which level tells people only to be prepared because a wave is possible?

Watch means a distant earthquake has occurred and a tsunami is possible. It is upgraded to a warning, the top level, once widespread flooding is expected, or cancelled if the threat fades.

A 1929 earthquake off Newfoundland set off a seabed landslide that raised a deadly tsunami and snapped twelve what?

Telegraph cables on the Atlantic floor broke one after another as the slide ran downslope. The order of the breaks later showed scientists that an avalanche of sediment had swept the seabed.

Which Sicilian port, facing the mainland across a narrow strait, was levelled by the 1908 earthquake and tsunami?

Messina's survivors were scattered: with the port almost completely destroyed, many of them had to be resettled in other Italian cities.

On which feast day in 1755 did an earthquake and tsunami devastate Lisbon?

All Saints' Day, 1 November, had filled the churches, which collapsed on the worshippers. Fires then burned across the city while the sea swept the waterfront.

In 563 CE a mountainside collapsed near the Rhône, sending a tsunami down which Alpine lake and reportedly over a city's walls?

Geneva, at the far end of the lake, was hit hard: chroniclers wrote that the water went over the city walls, and a 2012 survey of the lake bed found the slump of sediment that raised the wave.

The Storegga Slide, which sent a tsunami towards Britain about 8,000 years ago, happened in which sea?

The Norwegian Sea slide sent a wave across to Scotland, where its sands lie kilometres inland, and may have swamped Doggerland, the low country that once joined Britain to mainland Europe.

Tsunamis that cross entire oceans are known by what name?

Teletsunamis can do harm a whole ocean away: Japan's 2011 tsunami reached California about ten hours after the earthquake, did damage in Crescent City and swept a man out to sea nearby.

The most powerful earthquake of the 20th century, a magnitude 9.5 in 1960, struck which country?

Chile's 1960 earthquake near Valdivia raised a tsunami that crossed the whole Pacific in less than a day and still killed people on the coast of Japan.

The asteroid that ended the age of the dinosaurs struck which peninsula, where it is thought to have raised a giant tsunami?

Yucatán's Chicxulub crater marks the spot. One simulation put the first waves at up to 1.5 km high, and the surge may have run hundreds of miles inland.

World Tsunami Awareness Day honours a Japanese villager who guided neighbours to safety by setting fire to what on high ground?

His rice sheaves, newly harvested, lit the way to high ground in the dark after an 1854 earthquake. The UN chose the date, 5 November, as a day when lives were saved.