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Wednesday, January 4, 2017

How big can a tsunami really get?

In the video below, RealLifeLore looks at the science behind tsunamis and the question of just how massive they can actually become. And it's way bigger than we ever imagined – in some instances capable of creating waves that tower above the biggest buildings humankind has made.

There are two main causes of tsunamis: underwater explosions (like earthquakes or eruptions) and large volumes of material hitting the water (like meteorites or landslides).

What's happening in a tsunami is a principle called water displacement, where some other force or matter takes up the room the water was peacefully occupying and sends it racing off in different directions. The strength of the blast and the distance the water has to travel affects the overall size of the tsunami.

The Indian Ocean tsunami in 2004 was the deadliest tsunami in history and reached heights of 30 metres (or 98 feet). It was generated by a 9.1-magnitude earthquake that produced a greater force than all the explosives used in World War II combined – including the nuclear bombs.

The tsunami that hit Japan in 2011 was from a similarly sized quake to the one in 2004, but the resulting wave towered 40.5 metres (133 feet) into the air. That's just a few metres shorter than the Statue of Liberty.

But as devastating as those waves were, we're still just getting started in terms of potential tsunami size. There's a whole separate category of them, called megatsunamis, usually created by material sliding or falling into the water rather than an earthquake, which throws the waves up much higher.

One of the most tragic examples was the Vajont Dam disaster in 1963 in Italy, where a massive landslide into a dammed reservoir created a wave that reached 250 metres (820 feet) up into the air. It's estimated as many as 2,500 people were killed, but most of the dam structure stood firm and remains in place today. (more at BasementGeographer.

There was an even larger megatsunami than that though, in Lituya Bay, Alaska, in 1958. Again, a powerful landslide was to blame, and this time the terrifying wave reached a peak of 525 metres (1,722 feet) high. (More at

More at ScienceAlert.

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