6 Tsunami Myths That Refuse to Die

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🌊 Forget Hollywood. Here's what Really Makes Tsunamis Deadly
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Misinformation can cost lives.

After two years of breaking down natural hazards, I can confidently say:

Tsunamis are by far the most misunderstood.

That’s why I’ve gathered the 6 most common myths about tsunamis, and ranked them from the most widespread to the least known.

And of course, the least known is the deadliest.

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Myth #1 — A Tsunami Is Just One Giant Wave

Thank you, Hollywood.

From San Andreas to the more recent La Palma series on Netflix, the image is always the same:

A single, towering wave crashing onto the coast.

But a tsunami is abolutely not a one giant wave.

First a tsunami is not a wave, it’s a serie of waves.

And second they don’t break like surf waves.

It’s more like the sea level suddenly rising, quickly.

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But okay, I’ll give them that… it’s hard to make a rising sea level look impressive on screen.

I mean, a tsunami is just a surge of foam crawling up the beach… not exactly terrifying.

On rare occasions, yes, it can appear as a vertical wall of water.

But that has nothing to do with how powerful the tsunami actually is.

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Myth #2 — The Sea Recedes Before A Tsunami

Okay this one’s a half-myth.

It’s true… but only sometimes.

And that’s exactly what makes it dangerous.

Yes, an abnormal retreat of the ocean is a natural warning sign of an incoming tsunami.

But this sign doesn’t always happen. Far from it.

Here’s what a tsunami actually look like

Yes, waves. And like all waves, they are oscillations, with a positive part (the crest) and a negative part (the trough).

You see where I’m going with this?

If the trough of the first tsunami wave reaches the shore first, the sea will appear to recede.

But if the crest arrives first, the water level will suddenly rise, and with no warning at all.

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Myth #3 — Tsunamis Are Only Caused by Earthquakes

Earthquake-triggered tsunamis are the favorite of early warning agencies.

Because they’re easy to detect with modern sensors ,and they usually give enough time to alert coastal populations.

So “thankfully,” around 80% of tsunamis are caused by undersea earthquakes.

But there’s one type of tsunami that warning systems dread even more:

Underwater landslides.

They’re impossible to predict, and in many cases, go completely undetected.

Worse, they usually happen close to the shore, along the continental slope.

Which means the tsunami can sometimes form after it has already passed the offshore detection buoys placed farther out at sea.

It’s one of the only scenarios where a tsunami could strike a coastline without any warning.

Sure, it might not be as powerfull as a quake-generated tsunami…

But imagine even moderate waves hitting a densely populated coast with zero time to react.

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Myth #4 — Tsunamis Only Affect Coastal Areas

It should makes sense so why is it a myth?

It’s a wave in the ocean, so of course, it only hits the coast at a moment!

Yes but…

First, tsunamis don’t only happen in the ocean. You can have tsunamis in lakes.

After the 1980 eruption of Mount St. Helens, a massive landslide plunged into Spirit Lake and triggered a wave nearly 180 meters high.

But even if we go back to ocean tsunamis.

Even when they hit the coastline, it doesn’t mean their journey ends there.

Tsunamis can travel inland through rivers, bays, and narrow channels.

They follow the path of least resistance, and in somes cases, that path can leads deep into populated inland areas.

So no, living “a bit away from the coast” isn’t always safe.

If there’s a waterway nearby, the wave might reach you.

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Myth #5 — The Higher the Wave, the More Dangerous the Tsunami

Wave height says nothing about how dangerous a tsunami can be.

The 1958 Lituya Bay Megatsunami holds the record for the tallest tsunami wave ever: 525 meters.

Cause? A 30 million cubic meters of rock crashing into the bay.

How many deaths? Two.

The 2004 Sumatra tsunami is the deadliest in history: 227,000 fatalities.

Cause? A 9.3 underwater earthquake

Wave height? 35 meters.

Wave height depends mostly on the topography and bathymetry (underwater topography).

So why Lituya Bay’s wave was so tall?

Because a bay is enclosed. So the energy had nowhere else to go but upward.

But in the open ocean, tsunami energy spreads horizontally.

However an earthquake-generated tsunami releases far more energy and then is way more dangerous.

Even if its wave height is lower, the amount of energy it carries is incomparable.

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Myth #6 — Weak Earthquakes Can’t Cause Tsunamis

This one is, without a doubt, the deadliest of all.

Especially today when we can estimate earthquake magnitudes almost in real time.

Yes, estimate. It usually takes several days to get the final, accurate value. But that’s can be a topic for another week.

And yet… It’s entirely possible for a magnitude 7 quake to produce a wave that barely travels a few meters inland.

While a magnitude 5 quake, in the same area, could devastate the coastline for kilometers.

So what makes the difference?

Here’s how an earthquake-generated tsunami forms:

It’s the sudden vertical movement of the seafloor that pushes the water column and creates the tsunami.

The greater the vertical displacement, the more energy is transferred, and the more powerful the tsunami.

But earthquake magnitude doesn’t tell you that. It doesn’t describe how much the seafloor actually moved up or down.

So if a tsunami is caused by an earthquake, the real question should be:

What was the vertical displacement of the ocean floor?

Because ultimately, it’s the fault’s movement that governs the tsunami’s power.

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Final Words (For Quick Glancers)

• Myth #1 — A tsunami is just one giant wave​
  → It’s a series of waves, not a single wall of water, and the first one isn’t always the biggest.
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• Myth #2 — The sea always recedes before a tsunami​
  → Sometimes it does, sometimes it doesn’t. Don’t wait for a visual cue to evacuate.
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• Myth #3 — Only earthquakes cause tsunamis​
  → Landslides, both underwater and on land, can trigger tsunamis with zero warning.
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• Myth #4 — Tsunamis only affect coastal areas​
  → Tsunamis can move far inland through rivers, bays, and even hit landlocked lakes.
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• Myth #5 — The taller the wave, the more dangerous the tsunami​
  → Wave height ≠ energy. A smaller wave can carry far more destructive power.
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• Myth #6 — Weak Earthquakes Can't Cause Tsunamis​
  → It’s the vertical movement of the seafloor, not the magnitude, that drives tsunami power.

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Thank you for your time!
Hydrau

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