The 10 Deadliest Tsunamis of All Time

tsunami breeching an embankment and flowing into the city of Miyako, Japan

JIJI PRESS / AFP / Getty Images

When the ocean floor moves enough, the surface finds out about it — in the resulting tsunami. A tsunami is a series of ocean waves generated by large movements or disturbances on the ocean's floor. The causes of these disturbances include volcanic eruptions, landslides, and underwater explosions, but earthquakes are the most common. Tsunamis can occur close to the shore or travel thousands of miles if the disturbance occurs in the deep ocean. Wherever they occur, though, they often have devastating consequences for the areas they hit. 

For example, on March 11, 2011, Japan was struck by a magnitude 9.0 earthquake that was centered in the ocean 80 miles (130 km) east of the city of Sendai. The earthquake was so large that it triggered a massive tsunami that devastated Sendai and the surrounding area. The earthquake also caused smaller tsunamis to travel across much of the Pacific Ocean and cause damage in places like Hawaii and the west coast of the United States. Thousands were killed as a result of both the earthquake and tsunami and many more were displaced. Fortunately, it was not the world's deadliest. With a death toll of "only" 18,000 to 20,000 and Japan being particularly active for tsunamis throughout history, the most recent doesn't even make the top 10 deadliest.

Fortunately, warning systems are becoming better and more widespread, which can cut down on the loss of life. Also, more people understand the phenomena and heed the warnings to move to higher ground when a tsunami possibility exists. The 2004 Sumatran disaster spurred UNESCO to set a goal to establish a warning system for the Indian Ocean ​like exists in the Pacific and increase those defenses worldwide. ​​

The World's 10 Deadliest Tsunamis

Indian Ocean (Sumatra, Indonesia)
Estimated Number of Deaths: 300,000
Year: 2004

Ancient Greece (Islands of Crete and Santorini)
Estimated Number of Deaths: 100,000
Year: 1645 B.C.

(tie) Portugal, Morocco, Ireland, and the United Kingdom
Estimated Number of Deaths: 100,000 (with 60,000 in Lisbon alone)
Year: 1755

Messina, Italy
Estimated Number of Deaths: 80,000+
Year: 1908

Arica, Peru (now Chile)
Estimated Number of Deaths: 70,000 (in Peru and Chile)
Year: 1868

South China Sea (Taiwan)
Estimated Number of Deaths: 40,000
Year: 1782

Krakatoa, Indonesia
Estimated Number of Deaths: 36,000
Year: 1883

Nankaido, Japan
Estimated Number of Deaths: 31,000
Year: 1498

Tokaido-Nankaido, Japan
Estimated Number of Deaths: 30,000
Year: 1707

Hondo, Japan
Estimated Number of Deaths: 27,000
Year: 1826

Sanriku, Japan
Estimated Number of Deaths: 26,000
Year: 1896

A Word on the Numbers

Sources on death figures can vary widely (especially for those being estimated long after the fact), due to lack of data on populations in areas at the time of the event. Some sources may list the tsunami figures along with the earthquake or volcanic eruption death figures and not split out the amount killed just by the tsunami. Also, some numbers may be preliminary and are revised down when missing people are found or revised up when people die of diseases in coming days brought on by the floodwaters.

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Briney, Amanda. "The 10 Deadliest Tsunamis of All Time." ThoughtCo, Feb. 16, 2021, Briney, Amanda. (2021, February 16). The 10 Deadliest Tsunamis of All Time. Retrieved from Briney, Amanda. "The 10 Deadliest Tsunamis of All Time." ThoughtCo. (accessed March 31, 2023).