RealLifeLore

WATCH: How Big Can a Tsunami Really Get?

It's big. Very big.

DAVID NIELD
2 JAN 2017
 

With devastating tsunamis hitting Japan and the Indian Ocean in recent history, we're all too aware of the impact these natural disasters can have: but just how bad can they get?

 

In the video above, 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, sometimes known as a seismic sea wave.

The scariest parts of the video are the real-life examples of tsunami heights.

Take the Indian Ocean tsunami in 2004, which reached heights of 30 metres (or 98 feet), 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.

 

That's a wave roughly the same height as 17 adults standing on top of each other – and it's the deadliest tsunami in history – but in height terms, it's relatively small compared with some of the others our planet has seen.

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.

That's what happens when you have 260 million cubic metres (340 million cubic yards) of earth and rock disappear into a reservoir in less than a minute. It's estimated as many as 2,500 people were killed, but most of the dam structure stood firm and remains in place today.

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.

In other words, almost 100 metres (328 feet) above the tip of the Empire State Building.

If you find that scary, be thankful you weren't around on the Hawaiian island of Molokai about 1.5 million years ago. Here, a landslide from the side of a volcano generated a tsunami wave thought to have been 600 metres (1,968 feet) high, completely submerging the island.

In ancient Egyptian terms, that's four great Giza pyramids stacked on top of each other.

Last – but certainly not least – is the monster wave created by the asteroid smash that is thought to have wiped out the dinosaurs some 66 million years ago.

When it hit Earth, scientists think the asteroid would have released the same amount of energy as 2 million nuclear bombs, creating a wave some 5 kilometres (3.1 miles) high.

That's higher than most of the mountains on the planet, including the Matterhorn, and you'd have to get a lot more than half-way up Everest before you could avoid it.

Those poor dinos didn't stand a chance.

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