What are tsunamis?

Tsunamis are a series of very big and powerful ocean waves that get bigger and bigger as they reach the shore. The series of waves are called a wave train.

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Tsunamis usually start suddenly. The waves travel very quickly across the ocean. When they reach the shore they cause huge damage to buildings and vehicles. They can flood entire towns.


The meaning of a tsunami

The word tsunami comes from the Japanese word 'Tsu' meaning harbour and 'Nami' which means wave. Tsunamis are sometimes called tidal waves but this is confusing because they don’t actually have anything to do with the tides of the ocean.


What causes tsunamis?

Tsunamis are formed when the plates from the Earth’s crust move about. This makes a large amount of water suddenly move, creating a wave. As the wave moves it gets bigger and bigger.

Do you know what makes the plates from the Earth’s crust move? Usually, it’s an earthquake, volcanic eruption, or landslide. Sometimes it happens when glaciers break off or when meteorites hit the Earth. The biggest cause of tsunamis, however, are earthquakes.


A tsunami is coming!

When a giant wave is on its way to the shore, the water from the coastline pulls back really far. That’s how you know a tsunami is coming and you need to run!

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When the wave arrives on the shore, it looks like a giant wall of water. Some tsunamis have been 100 feet high. After the big wave, more waves arrive, sometimes several minutes after.


Did you know?

  • Most tsunamis are small and are not noticed.
  • Tsunamis can travel up to 805 kilometres per hour.
  • A tsunami that hit Hawaii in 1946 was travelling so fast it was almost as fast as a jet plane.