Geography

Plate Tectonics: Tsunamis

What is a tsunami?

A tsunami is a series of large waves, often over 5m high. They are completely unrelated to the astronomical tides, which sets them apart from other large waves. They are not always necessarily caused by seismic disturbances and can be formed in other ways too. They often look like walls of water and can be dangerous for hours, as there are generally multiple waves, coming each 5-60 minutes. The first wave is not necessarily always the largest, with the largest sometimes being the second, third, fourth or even fifth wave.

How are tsunamis formed?

Tsunamis are formed when a force displaces a body of water. This could be due to earthquakes, volcanic eruptions, landslides and even comets and asteroids hitting Earth.

How do earthquakes form tsunamis?

The plates move into each other, getting stuck as they do so. However, the plate keeps attempting to move, creating strain energy. This energy is then eventually released by one of the plates flicking upwards, displacing the water of the ocean as it does so, sending a large wave towards the shore, a tsunami. This tsunami will not stop. It is a wall of water, the only way that it will subside is by coming into contact with high ground.

Why are tsunamis so dangerous?

Tsunamis are very powerful walls of water, which smash into the shoreline, traveling at speeds of over 500mph. They obliterate all that stands in their way, picking up houses, boats, cars and any number of other things with them as they go. If the water doesn’t kill you, the debris certainly will. They leave fires, floods and even occasionally nuclear meltdown in their wake. You also cannot generally see them coming, especially without the aid of technology. Even if you do know there is one on its way, escaping isn’t always possible with the limited time.

Worst tsunamis of all time:

1. Indian Ocean Tsunami (2004)

Max height: 51m Death toll: 227, 898

2. Messina Earthquake and Tsunami (1908)

Max height: 12m Death toll: 80,000 (from both disasters)

3. Valdivia Earthquake and Tsunami (1960)

Max height: 25m Death toll: 1,000-6,000 (from both disasters)

4. Tohoku Earthquake and Tsunami (2011)

Max height: 40.5m Death toll: 19,747 (from both disasters)

5. Sunda Strait Tsunami (2018)

Max height: 5m Death toll: 437