What Makes Tsunamis So Deadly? Shocking Facts You Should Know

By Sushant Agarwal

Published on | Jul 30, 2025

Tsunamis: Nature’s Most Powerful Shockwaves

Tsunamis are massive ocean waves triggered by sudden underwater disturbances. They can cross oceans in hours and devastate coastlines.

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How Earthquakes Trigger Tsunamis

Tectonic plates shifting under the sea can violently push or drop the seabed, displacing vast amounts of water and unleashing tsunami waves.

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Other Causes Beyond Earthquakes

Volcanic eruptions, landslides, massive storms, or even meteorite impacts can generate tsunami waves powerful enough to destroy coastal areas.

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Krakatoa 1883: A Historic Eruption

The Krakatoa volcano exploded with such force that it created a deadly tsunami killing 30,000 people—heard 4,500 km away.

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Why It's Called a 'Tsunami'

“Tsunami” means “harbour wave” in Japanese. It’s more accurate than “tidal wave,” which wrongly links it to tides.

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How Tsunamis Grow in Size

In deep ocean, tsunami waves are small and spread out. But as they near shore, they compress and rise into towering, destructive waves.

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Ancient Roman Account of a Tsunami

In 365 AD, Roman historian Ammianus Marcellinus described the sea vanishing—followed by giant waves swallowing ships and people.

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Warning Signs Before a Tsunami

The sudden retreat of the ocean is often the first visible sign. It can be followed by several large waves over hours—or even days.

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What Makes a Tsunami So Destructive

The quake’s magnitude, sea floor shape, water displacement, and coastal barriers all affect how deadly the resulting tsunami is.

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2004 Indian Ocean Tsunami

A 9.1 quake off Sumatra triggered one of the deadliest tsunamis in history, killing over 220,000 people across 11 nations.

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