How tsunamis work – Alex Gendler


In 479 BC, when Persian soldiers besieged the Greek city of Potidaea, the tide retreated
much farther than usual, leaving a convenient invasion route. But this wasn’t a stroke of luck. Before they had crossed halfway, the water returned in a wave higher
than anyone had ever seen, drowning the attackers. The Potiidaeans believed
they had been saved by the wrath of Poseidon. But what really saved them was likely the same phenomenon
that has destroyed countless others: a tsunami. Although tsunamis are commonly
known as tidal waves, they’re actually unrelated
to the tidal activity caused by the gravitational forces
of the Sun and Moon. In many ways, tsunamis are just
larger versions of regular waves. They have a trough and a crest, and consist not of moving water, but the movement of energy through water. The difference is
in where this energy comes from. For normal ocean waves,
it comes from wind. Because this only affects the surface,
the waves are limited in size and speed. But tsunamis are caused by energy
originating underwater, from a volcanic eruption, a submarine landslide, or most commonly,
an earthquake on the ocean floor caused when the tectonic plates
of the Earth’s surface slip, releasing a massive amount
of energy into the water. This energy travels up to the surface, displacing water and raising it above
the normal sea level, but gravity pulls it back down, which makes the energy ripple
outwards horizontally. Thus, the tsunami is born, moving at over 500 miles per hour. When it’s far from shore,
a tsunami can be barely detectable since it moves through
the entire depth of the water. But when it reaches shallow water,
something called wave shoaling occurs. Because there is less water
to move through, this still massive amount
of energy is compressed. The wave’s speed slows down, while its height rises
to as much as 100 feet. The word tsunami,
Japanese for “harbor wave,” comes from the fact that it only seems
to appear near the coast. If the trough of a tsunami
reaches shore first, the water will withdraw
farther than normal before the wave hits, which can be misleadingly dangerous. A tsunami will not only drown
people near the coast, but level buildings and trees
for a mile inland or more, especially in low-lying areas. As if that weren’t enough,
the water then retreats, dragging with it the newly created debris, and anything, or anyone,
unfortunate enough to be caught in its path. The 2004 Indian Ocean tsunami was one of the deadliest
natural disasters in history, killing over 200,000 people
throughout South Asia. So how can we protect ourselves
against this destructive force of nature? People in some areas have attempted to stop tsunamis
with sea walls, flood gates, and channels to divert the water. But these are not always effective. In 2011, a tsunami
surpassed the flood wall protecting Japan’s Fukushima Power Plant, causing a nuclear disaster in addition to claiming over 18,000 lives. Many scientists and policy makers
are instead focusing on early detection, monitoring underwater pressure
and seismic activity, and establishing global
communication networks for quickly distributing alerts. When nature is too powerful to stop, the safest course
is to get out of its way.

100 thoughts on “How tsunamis work – Alex Gendler

  1. thanks, y’all just helped me write my science essay that’s due tomorrow. time? 3:47 am l love you middle school❤️

  2. Tsunami is named by the Japanese so you also know it's not like I like YOU! Looks away*

    -tsundere

  3. How can we stop it? We have to use a Ted-Ed riddle answers!

  4. Why are people building walls I know the perfect solution:

    GET TO HIGH GROUND FOR GOD SAKE

  5. Of course a wall isn’t going to work! I have an idea but I don’t know if it will work on the tsunamis. The idea is to create land bumps under the sea hopefully this will slow down the tsunami and weaken it at the same time

  6. Tsunami: here I come

    Person: let’s record
    : )
    Tsunami: am I a joke to you ?!

  7. Don't get out of its way when it's right next to you! It's gonna be too late

  8. how about harp when they caused the one on christmas day 2005 or the fukushima one. jolly good show

  9. Wouldn’t the Potiideans die too from the tsunami in the beginning?

  10. or get out of its way HOW AM I supposed to do that The ocean is like miles and miles and miles ahead ;w;

  11. Never knew a natural disaster can cause a natural disaster.

  12. Who’s here after the second earthquake in California and fears a big one?

  13. for those raised in metric system, Tsunamis's travel 800km/h and reaching heights of 6,000 m.

  14. The people in that Ancient Greek city Potidaea take the crown for the luckiest people in history ?

  15. Damn. I remember the 2004 Tsunami. I was asleep when it happened, but I woke up and went to the balcony and I saw a huge flood. At first I thought it was heavy rain, but it was too much. An uncle said it must have been a tsunami.

  16. I’m watching this while I’m on the coast of California so ummmmmmmm…

  17. I’m watching this while I’m on the coast of California so ummmmmmmm…

  18. I don't understand abit. When the tsunami came at 2:16, there was fire on a building?

  19. this is very helpful and I will recommend it to other classmates who need help with their assessments.

  20. if i was in a tsunamis i would just standed there because theres no point in running when your going to die its way to big to escap

  21. Well she said to get out of its way???
    Um the wave is to wide, you can't even see the edge. If your close to it, your dead!

  22. Thanks a lot, it helped me to learn about Tsunamis quite easily than reading thousands of text in books & explanation is nice.

  23. I Once Expirienced A GIIIAAANT Wave.
    It Was 80 Feet And Its Speeds Were Severe/Almost Critical Reaching From 84 mph To 399 mph
    Not Really A Tsunami But The Damage From The Wave It Self Was 7 000 000 000$ Dollars

    And I Experienced A Tsunami Too It Was 100 Feet And Its Speeds Were Critical Reaching From A Dangerous 170 mph To 500 mph
    And 8 000 000 000 $ Dollars Went Just For A Tsunami 😐

    Im The Unlickiest Person On Earth. :/

  24. Oh Also The Wave I Expirienced Was A Reverse Wave.
    Do You Know What A Reverse Wave Is?
    Its When A Wave Turns The Other Way That It Came From.
    It Starts With A Massive Amount Of Water Wrecking The First Side Of The Shore/People And Then The Shore Becomes Very Big
    After That The Wave Travels The Other Way And It Wrecks The Other Shore Too And After That It Dies.
    Unfortunaley The Wave Was Triple
    Only One Headed-It Lasts Only A Few Seconds From 2 Secs To 27 Secs All Though Its Powerfull Enough To Wreck A Car
    Double Headed-It Last From 3 Mins To 21 Mins With Its Big Stamina It Can Go Both Directions It Is Able To Split In Half The One Half Goes The Left Way The Second Half Goes The Other Way
    Tripple Headed:This One Is Severe It Lasts From 3 Hrs To 15 Hrs Its So Powerfull That It Can Destory Everything On Its Way(Except The Sky.Duh)
    Quadrople Headed:Better Watch Out For This One Its Critical Its Almost Like The Tsunami It Can Take Half And A Quarter Of A Tsunami Plus It Lasts From 24 Hrs To 2 Days.
    Things That Can Happen From The One Headed Wave:A Mini Flooding,Destroyed Cars And Some Cracked Buildings,Light Lighting And Light Hail.
    This That Can Happen From The Double Headed Wave:A Medium Flooding,Only Half Of Buildings Left,Demolished Cars,A lot Of Damage Repair,Injuries,19% Chance Of Death,Medium Lighting,Medium Hail And May Go Both Ways.(Left And Right)
    This That Can Happen From The Triple Headed Wave:Dead People,Severe Injuries,Destroyed Buildings,Ripped Into Pieces Cars,A Big/Large Flooding,May Split In Three Directions,Half Continet Underwater,Can Easily Sink Small Continets,Heavy Lighting And Heavy Hail.
    Things That Can Happen From The Quadrople Headed Wave,Goes Four Ways(North South East And West)Demolished Buildings,Most Of The People In The Continent Will Die,Critical/Fatal Injuries,Can Sink Big Or Small Continents Easily,Very Heavy Lighting,Visibility Can Go As Dim As 6 Decemeters Visibility And Very Heavy Hail.
    Reverse Wave:Its A One Headed Wave That Goes Left And Right With The Same Amount Of Things As The One Headed Wave All Though Its 0.6% Stronger

  25. In My Country We Also Put A Wall As High As 60 Feet But The Severe Wave I Was Telling About Broke The Wall Like Nothing.

  26. HH thank you
    I only know the tsunami is case by the undersea water
    But I never know the reason in this
    HH,now I know
    (The piece of the crust press against each other ,causing the stress.Then cause the actual length of rock bent or store energy.Stress level overcome frictional resistance,the rocks crack,slip.Then release the massive energy into the water,)

  27. thank you for this video. I had to do a presentation about tsunami and this video really helped me and also made me realise how dangerous tsunamis can be!!!!!!

  28. TSUNAMI ARE MADE BY THE COLLAPSE OF THE LAND INSIDE THE OCEAN ,, COLLAPSE OF THE LAND CAUSES OF POLLUTION AND EARTHQUAKE

  29. Hello! I noticed that there is a surfer briefly pictured. Is this meant to reference Felipe Pomar?

  30. Tsunami cause by a volcanic eruption, submarine landslide and earthquake under the water

  31. TSUNAMI ARE MADE OF COLLAPSE OF THE LAND INSIDE THE OCEAN CAUSES OF THE DEATH OF LAVA INSIDE THE LAND, AFTER THE DEATH OF LAVA THIS ARE CREATING A GIANT AND DEEP CAVE AND IF THIS ARE COLLAPSE GIANT WAVE ARE MADE,,, THE MOVING OF LAND EXPLAINING OF MANY SCIENTIST ARE WRONG

  32. People have built walls to prevent the after effect of tsunami
    .
    .
    .
    Nature – LOL nice try

  33. Posedion caused the tsuamnis. Tsumani are bigger waves. Read the greek mythology and roman gods. 12 olmypians gods.

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