Humanities › Geography The 10 Deadliest Tsunamis of All Time Share Flipboard Email Print JIJI PRESS / AFP / Getty Images Geography Physical Geography Basics Political Geography Population Country Information Key Figures & Milestones Maps Urban Geography By Amanda Briney Geography Expert M.A., Geography, California State University - East Bay B.A., English and Geography, California State University - Sacramento Amanda Briney, M.A., is a professional geographer. She holds a Certificate of Advanced Study in Geographic Information Systems (GIS) from California State University. our editorial process Amanda Briney Updated July 30, 2019 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: 300,000Year: 2004 Ancient Greece (Islands of Crete and Santorini)Estimated Number of Deaths: 100,000Year: 1645 B.C. (tie) Portugal, Morocco, Ireland, and the United KingdomEstimated Number of Deaths: 100,000 (with 60,000 in Lisbon alone)Year: 1755 Messina, ItalyEstimated 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: 40,000Year: 1782 Krakatoa, IndonesiaEstimated Number of Deaths: 36,000Year: 1883 Nankaido, JapanEstimated Number of Deaths: 31,000Year: 1498 Tokaido-Nankaido, JapanEstimated Number of Deaths: 30,000Year: 1707 Hondo, JapanEstimated Number of Deaths: 27,000Year: 1826 Sanriku, JapanEstimated Number of Deaths: 26,000Year: 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.