World's Worst Tsunamis

The tragic repercussions when giant walls of water make landfall

The word tsunami is derived from two Japanese words meaning "harbor" and "wave." Rather than a single wave, a tsunami is actually a series of huge ocean waves called “wave trains” that result from sudden changes in the ocean floor. The most frequent cause of a major tsunami is an earthquake measuring greater than 7.0 on the Richter scale, although volcanic eruptions and underwater landslides can also trigger them—as can the impact a large meteorite, however, that’s an extremely rare occurrence.

What Causes a Tsunami?

The epicenters for many tsunamis are areas in the Earth’s crust known as subduction zones. These are places where tectonic forces are at work. Subduction happens when one tectonic plate slides beneath another, forcing it to descend deep into the Earth's mantle. The two plates become "stuck" due to the force of friction.

Energy builds in the upper plate until it surpasses the frictional forces between the two plates and snaps free. When this sudden movement happens close enough to the surface of the ocean floor, the huge plates are forced up, displacing enormous amounts of seawater, and triggering a tsunami that spreads out from the epicenter of the earthquake in every direction.

Tsunamis that begin in open water can appear as deceptively small waves, but they travel at such amazing rates of speed that by the time they reach shallow water and the shoreline, they can reach heights of up to 30 feet or more, while the most powerful can attain heights well over 100 feet. As you can see from this list the worst tsunamis in history, the consequences can be truly devastating.

Boxing Day Tsunami, 2004

A fishing trawler washed up in Banda Aceh

Jim Holmes / Getty Images

Even though this was the third-greatest magnitude earthquake recorded since 1990, the magnitude 9.1 temblor is best remembered for the deadly tsunami that the undersea quake unleashed. The earthquake was felt in Sumatra, parts of Bangladesh, India, Malaysia, the Maldives, Myanmar, Singapore, Sri Lanka, and Thailand. The ensuing tsunami hit 14 countries as far away as South Africa.

The fault line that shifted causing the tsunami has been estimated at 994 miles in length. The U.S. Geological Survey estimated that the energy released by the tsunami-triggering quake was equivalent to 23,000 Hiroshima-type atomic bombs.

The death toll from this disaster was 227,898 (about a third of those children), making it the sixth-deadliest recorded disaster in history. Millions more were left homeless. In the aftermath, a massive outpouring of $14 billion in humanitarian aid was sent to the affected countries. Tsunami awareness has increased dramatically, resulting in numerous tsunami watches in the wake of subsequent underwater seismic events.

Messina, 1908

Aftermath of a tsunami in Messina in 1908

Hulton Archive / Getty Images

Picture "the boot" of Italy. Now, travel down to the toe. It's there you'll find the Strait of Messina that separates Sicily from the Italian province of Calabria. On December 28, 1908, a 7.5 magnitude quake—massive by European standards—struck at 5:20 a.m. local time, sending 40-foot waves crashing into both shorelines.

Modern-day research suggests that the quake actually triggered an undersea landslide that touched off the tsunami. The waves devastated coastal towns including Messina and Reggio di Calabria. The death toll was between 100,000 and 200,000, with 70,000 fatalities in Messina alone. Many of the survivors joined a wave of immigrants who left Italy for the United States.

Great Lisbon Earthquake, 1755

Aftermath of the Great Lisbon Earthquake in 1755
Bettmann Archive / Getty Images

On November 1, 1755, at about 9:40 a.m. an earthquake estimated between 8.5 and 9.0 on the Richter scale with its epicenter in the Atlantic Ocean off the coasts of Portugal and Spain shook the surrounding area. The temblor took its toll on Lisbon, Portugal for only a few moments, but about 40 minutes after the shaking stopped, the tsunami hit. The double disaster sparked the third wave of devastation setting off raging fires throughout urban areas.

The tsunami traveled a wide swath, with waves as high as 66 feet striking the coast of North Africa and others reaching Barbados and England. The death toll from the trio of disasters is estimated at 40,000 to 50,000 across Portugal, Spain, and Morocco. Eighty-five percent of Lisbon's buildings were destroyed. The contemporary study of this quake and tsunami is credited with giving rise to the modern science of seismology.

Krakatoa, 1883

Krakatau volcano erupting

Tom Pfeiffer / VolcanoDiscovery / Getty Images 

This Indonesian volcano erupted in August 1883 with such violence that all 3,000 people on the island of Sebesi, eight miles from the crater, were killed. The eruption, spewing fast-moving clouds of hot gas and sending mammoth rocks plunging into the sea set off waves that ranged from 80 to nearly 140 feet and demolished entire towns.

The volcanic explosion was reportedly heard 3,000 miles away. The resulting tsunami reached India and Sri Lanka, where at least one person was killed, and the waves were felt as far away as South Africa. All told, an estimated 40,000 lives were lost, with most of those deaths attributed to the tsunami waves.

A lasting reminder of the calamitous event has long been the remaining volcano, Anak Krakatoa. Also known as “the Child of Krakatoa,” this volcano erupted in 2018, triggering another tsunami as it collapsed in on itself. When the waves hit land, they were about 32 feet high, however, they'd already dissipated considerably by then.

Researchers estimate that at its peak, this tsunami reached heights somewhere between 330 and 490 feet in height—or taller than the Statue of Liberty. Fortunately, when it made landfall, the island it slammed into was uninhabited. Had the tsunami been traveling in the direction of populated areas, it could easily have resulted in the most destructive natural disaster of modern times.

Tōhoku, 2011

Town destroyed by the tsunami in Japan

Masaaki Tanaka / Sebun Photo / Getty Images

Sparked by an offshore magnitude 9.0 earthquake on March 11, 2011, waves reaching as high as 133 feet crashed into the east coast of Japan. The destruction resulted in what the World Bank called the most expensive natural disaster on record, with an economic impact of $235 billion. More than 18,000 people lost their lives.

The raging waters also set off radioactive leaks at the Fukushima Daiichi nuclear power plant and sparked a global debate on the safety of nuclear energy. Waves from this tsunami reached as far as Chile, which saw a six-foot surge.

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