The science behind tsunamis

KSDK – A magnitude 8.0 earthquake off the coast of northern Chile has sparked a tsunami warning for numerous surrounding coastal areas, leading to large-scale evacuations.

You might be wondering how, exactly, tsunamis work. We have a quick look below:

-What is a tsunami? A tsunami is a series of large waves triggered by an earthquake, landslide or volcanic eruption. Earthquakes generate tsunamis if the sea floor shakes violently enough to displace massive amounts of water. The first wave of a tsunami is not necessarily the most destructive, and the waves can be as long as 60 miles and as far as one hour apart.

-How fast do they travel? In deep water, tsunamis can reach speeds of up to 500 miles per hour. They can be barely a ripple in the open ocean, but rise dramatically as they near the coast and enter shallow water.

-How high were recent tsunamis in Japan and the Indian Ocean? Some reports estimate that 2004's Indian Ocean tsunami was was up to 30 feet deep in some places,claiming 200,000 lives. Waves after a record-setting earthquake spawned a devastating tsunami in Japan topped 60 feet – with some growing to more than 100 feet high. More than 15,000 people are confirmed dead.

-What are the warning signs? Earthquakes are the biggest indicators of tsunamis, and some witnesses say they've noticed a fall or rise in water level just before the waves hit. Others say tsunamis sound like a freight train.

-Where do they usually hit? The Pacific takes the brunt of tsunamis, but they've been generated around the world. The Caribbean has been hit by 37 verified tsunamis since 1498.

-What's the math behind tsunamis? Partially through this handy equation, which says that speed is dependent upon the square root of acceleration due to gravity multiplied by the depth of water. A tsunamis amplitude, meanwhile, is determined by the amount by which the sea-floor is displaced. Wavelength and the period of the tsunami is determined by the size and shape of the underwater disturbance.

-What's up with the word 'tsunami' anyway? Tsunami is a Japanese word with the English translation 'harbor wave.'

-How do scientists detect tsunamis?

Scientists gather data with tide gages and tsunami buoys in the deep ocean.

If they detect an earthquake above a magnitude 7.0, it is generally automatically considered a tsunami hazard.


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