Hey everyone, welcome back to My Weird Prompts. I am Corn, and I am joined as always by my brother.
Herman Poppleberry, at your service. And man, Corn, do we have a heavy one today. Our housemate Daniel was telling us about this dream he had last night. Apparently, it was a pretty vivid nightmare about a tsunami hitting a coast, and he was scrambling for higher ground.
Yeah, he mentioned that this morning while we were having coffee. It is funny how a dream can just stick with you and make you realize how little you actually know about a topic. Daniel was asking some really pointed questions about whether any coastal area is truly safe and what these things actually look like in real life versus the movies.
It is a great prompt because tsunamis are one of those natural disasters that we think we understand because we have seen the Hollywood versions, but the actual physics of them is much weirder and, in some ways, much scarier than a big surfing wave.
Exactly. I think most of us have that image of the massive, curling wave from Deep Impact or something similar. But Daniel pointed out that the actual footage he has seen looks more like a wall of water or a rapidly rising tide that just does not stop. So, Herman, I want to dive into this. Is every coast at risk? And what are we actually looking at when a tsunami strikes?
Well, to answer the first part of Daniel's question, geographically speaking, almost any coastal area can technically be at risk, but the level of risk varies wildly depending on where you are in relation to tectonic plate boundaries. About eighty percent of all tsunamis happen within the Pacific Ocean's Ring of Fire. That is where you have these massive subduction zones where one plate is sliding under another. When those plates slip, they displace a massive volume of water.
Right, so the Pacific is the big one. But Daniel was mentioning that he has seen tsunami evacuation signs in Tel Aviv, which is on the Mediterranean. We live up here in Jerusalem, so we are at quite a high elevation, about seven hundred and fifty meters above sea level, but Tel Aviv is right there. Does the Mediterranean have a real risk?
It absolutely does. In fact, historical records show that the Mediterranean has a long history of tsunamis. They are less frequent than in the Pacific, but they can be devastating because the basin is so small. If an earthquake happens off the coast of Greece or Crete, the tsunami could reach the Israeli coast in as little as thirty to sixty minutes. There is not a lot of time for warning. About ten percent of all tsunamis globally actually occur in the Mediterranean.
That is a much higher percentage than I would have guessed. You usually think of the Indian Ocean or Japan. But let us talk about what Daniel mentioned regarding the shape of the wave. He said he always pictured a steep wave, but the footage shows a wall of water. Why is that? What is the actual physical difference between a regular ocean wave and a tsunami?
This is where the physics gets really fascinating. A regular wave, the kind you see surfers on, is caused by wind. Wind blows across the surface of the water and creates ripples that grow into waves. The energy of a wind wave is concentrated near the surface. The water moves in a circular motion, but the actual wave itself has a relatively short wavelength, maybe a few hundred feet at most.
Okay, so it is a surface phenomenon.
Exactly. But a tsunami is a whole different beast. It is not caused by wind; it is caused by the displacement of the entire water column from the seafloor to the surface. Imagine you are in a bathtub and you suddenly push your hand upward from the bottom. You are moving all that water at once. A tsunami can have a wavelength of over one hundred miles. That means the distance from one crest to the next is one hundred miles long.
Wow. So, when that hits the coast, it is not just a single wave that breaks and then recedes.
Precisely. Because the wavelength is so long, a tsunami acts more like a fast-rising tide that just keeps coming and coming for ten, fifteen, or even thirty minutes. It is a massive volume of water. When it is out in the deep ocean, it might only be one or two feet high, and ships won't even notice it passing under them. But it is traveling at the speed of a jet plane, maybe five hundred miles per hour.
Five hundred miles per hour? That is incredible. So, as it gets closer to the shore and the water gets shallower, all that energy has to go somewhere, right?
You nailed it. It is a process called shoaling. As the front of the wave hits the shallow water of the continental shelf, it slows down significantly, maybe down to thirty or forty miles per hour. But the back of the wave, which is still fifty miles out at sea, is still moving at hundreds of miles per hour. The water starts to pile up. The wavelength shrinks, and the height increases dramatically.
And that is why it looks like a wall of water. It is not a breaking wave; it is a massive surge.
Right. It is often described as a bore. It looks like the ocean has simply decided to move inland. And because there is so much mass behind it, it does not just hit the beach and stop. It carries everything with it—cars, trees, houses—and that debris then turns into a grinding slurry that destroys everything in its path.
That is a terrifying image. Daniel also asked about minor tsunamis. Do we have small ones that happen frequently but just don't make the news?
Oh, all the time. There are minor tsunamis happening constantly that are only detectable by sensitive pressure sensors on the ocean floor. An earthquake of magnitude six point five might trigger a tsunami that only results in a six-inch rise in sea level. If you were standing on the beach, you might just think it was a slightly weird tide. But those are still technically tsunamis.
So, it is a spectrum. It is not just the massive disasters like the one in two thousand four in the Indian Ocean or the two thousand eleven one in Japan.
Exactly. And there are also things called meteotsunamis. These aren't caused by earthquakes at all, but by rapid changes in atmospheric pressure, often during fast-moving storms. They can cause a sudden surge of water that looks and acts just like a small tsunami. They happen in the Great Lakes in the United States, in the Mediterranean, and all over the place. Most people just call them rogue waves or freak tides, but the mechanism is very similar to a tsunami.
I remember reading about those. They can be quite dangerous for people on piers or small boats because they come out of nowhere without an earthquake warning. But going back to Daniel's question about geography, he asked if any coastal area that isn't dramatically elevated is at risk. Are there places that are naturally shielded?
Some places are more protected than others. For example, if you are deep inside a very narrow, winding fjord with a shallow entrance, the energy of a tsunami might dissipate before it reaches you. However, the opposite can also happen. Some bays are shaped like funnels, and they actually concentrate the energy of the tsunami, making it much higher and more destructive when it reaches the end of the bay. This is what happened in Hilo, Hawaii, several times in the twentieth century.
That makes sense. The geometry of the coastline matters as much as the distance from the earthquake. Now, Herman, you mentioned that eighty percent happen in the Pacific. What about the Atlantic? People often think the Atlantic is safe, but there was that famous earthquake in Lisbon back in the seventeen hundreds.
You are right to bring that up. Seventeen fifty-five, the Great Lisbon Earthquake. It triggered a massive tsunami that devastated the coast of Portugal and even reached across the ocean to the Caribbean. While the Atlantic doesn't have as many subduction zones as the Pacific, it does have some, like the South Sandwich Trench and the Puerto Rico Trench. Also, you can have tsunamis caused by underwater landslides or volcanic collapses.
Wait, volcanic collapses? Like a whole side of a mountain falling into the sea?
Exactly. There has been a lot of talk over the years about the Cumbre Vieja volcano on the island of La Palma in the Canary Islands. There is a theory that if a massive chunk of that island were to slide into the ocean during an eruption, it could create a mega-tsunami that would travel across the Atlantic and hit the East Coast of the United States.
I have heard of that. Is that a realistic threat, or is it more of a doomsday movie scenario?
It is a subject of a lot of debate among geologists. Most current research suggests that a total collapse is unlikely to happen all at once. It would probably happen in smaller stages, which would still create tsunamis, but not the thousand-foot-high waves that some of the earlier models predicted. Still, the point is that you don't always need an earthquake to have a tsunami. Landslides are a major cause.
That leads me to another thought. Daniel was worried about being near the coast. If you are in a place like Tel Aviv, what is the actual protocol? You see those signs with the person running up a hill. How high do you actually need to get?
That is a great question. Generally, the rule of thumb is to get at least thirty meters, or about one hundred feet, above sea level, or go at least two miles inland. In a place like Tel Aviv, which is relatively flat, your best bet is often vertical evacuation. That means getting to the third or fourth floor of a reinforced concrete building.
Vertical evacuation. That seems more practical in a city than trying to drive out of town, especially since everyone else would be doing the same thing.
Exactly. Traffic jams are a huge danger during tsunami evacuations. If you look at the footage from Japan in two thousand eleven, you see lines of cars stuck on the roads as the water approaches. If you are in a sturdy, modern building, going up is often much safer than trying to outrun it in a car.
You know, it is interesting that Daniel had this dream while we are living in Jerusalem. I mean, we are safe here, but it makes you think about the vulnerability of modern civilization. So much of our infrastructure, our power plants, our fiber optic cables, our ports—they are all at sea level.
It is incredibly vulnerable. Think about the Fukushima Daiichi nuclear disaster. That wasn't caused by the earthquake itself—the plant actually survived the shaking quite well. It was the tsunami that overtopped the sea wall and flooded the backup generators. Without power to cool the reactors, they had a meltdown. That is a perfect example of a second-order effect. It wasn't just the water; it was what the water did to the technology we rely on.
That is a chilling point. We build these systems assuming a certain level of stability, but nature can just reset the board in an instant. Herman, how do we monitor these things now? I know we have better systems than we did in two thousand four.
We have made massive strides. The gold standard now is the DART system, which stands for Deep-ocean Assessment and Reporting of Tsunamis. These are buoys anchored to the seafloor with incredibly sensitive pressure sensors. They can detect a change in water level of less than a millimeter in the deep ocean. When they detect a tsunami pulse, they beam that data to a satellite, which sends it to warning centers in Hawaii and Alaska.
A millimeter? That is incredible sensitivity for something sitting at the bottom of the ocean.
It really is. It allows scientists to model exactly how the tsunami will propagate and which coastal areas will be hit and when. In two thousand four, there was almost no warning system in the Indian Ocean. Today, there are sensors all over that basin. It doesn't stop the wave, but it gives people those precious minutes or hours to get to high ground.
It is amazing how much of our safety depends on these invisible networks of sensors. But even with all that tech, there is still the human element. People have to know what to do when the siren goes off.
And that is the hardest part. Education is key. One of the most important natural warning signs is the sea receding. If you are at the beach and you suddenly see the water pull back way further than a normal tide, exposing fish and coral that are usually underwater, you do not go out to look at it. You run.
Right, because that is the trough of the wave arriving before the crest. It is literally sucking the water away to build up that wall we talked about.
Exactly. In the two thousand four tsunami, many people were killed because they were curious and went out onto the newly exposed seabed. They didn't realize that the water would come back with a vengeance in just a few minutes.
It is a counterintuitive thing. You see something amazing and you want to investigate, but in that case, curiosity is literally fatal. Herman, you mentioned the frequency earlier. Major tsunamis—the ones that cause thousands of deaths—how often do those actually happen on a global scale?
On average, a major, destructive tsunami happens about twice a decade. But they tend to come in clusters because seismic activity can be cyclical. We had a very quiet period for a while, and then the early two thousands were incredibly active. It is hard to predict exactly when the next big one will hit, but we know the locations that are most likely. The Cascadia Subduction Zone off the coast of the Pacific Northwest in the United States and Canada is one that geologists are very worried about. It hasn't had a major rupture since the year seventeen hundred, and it is way overdue.
The Cascadia one is the stuff of nightmares. I have read that it could produce an earthquake of magnitude nine point zero or higher. That would send a tsunami into Seattle, Portland, and Vancouver.
And the coastal towns would have almost no time. We are talking about fifteen to twenty minutes of warning. That is why they are building these massive vertical evacuation structures in places like Ocosta, Washington. They are literally reinforced platforms on top of schools where the whole community can go.
It is a strange way to live, always having one eye on the horizon. But I suppose it is no different than living in a tornado alley or near a fault line. It is just about understanding the risk and being prepared.
Precisely. And that brings us back to Daniel's dream. It is a healthy kind of fear, in a way. It makes you realize that the world is a dynamic, sometimes violent place, and we are just guests on these tectonic plates.
Well, I think we have thoroughly explored the anatomy of a tsunami. From the physics of the water column to the dangers of the Mediterranean and the importance of vertical evacuation. It is definitely not just a big wave.
Not at all. It is more like the entire ocean moving onto the land. It is a powerful reminder of why we need to respect the sea.
Absolutely. And you know, speaking of the sea, I was thinking about some of the other things Daniel mentioned. He was curious if there are any places that are truly safe. I mean, if you are on a small island in the middle of the ocean, is a tsunami actually less dangerous than if you are on a continental coast?
That is an interesting nuance. If the island is very steep and has deep water all around it, the tsunami might not shoal as much. The water might just rise and fall relatively quickly without that massive wall effect. But if the island has a large coral reef or a shallow lagoon, the water will pile up just like it does at the coast. So, being on an island isn't necessarily a guarantee of safety. It all comes back to that underwater topography.
It really is a complex interaction of energy and geography. Herman, I have to ask, because you love the weird details—what is the largest tsunami ever recorded? I don't mean the most deadly, but the one with the highest actual wave.
Oh, that is a great one. It happened in nineteen fifty-eight in Lituya Bay, Alaska. It wasn't caused by an earthquake directly, but by a massive landslide triggered by an earthquake. An entire mountainside fell into the narrow bay. It created a splash wave that reached an incredible height of one thousand seven hundred and twenty feet.
One thousand seven hundred and twenty feet? That is higher than the Empire State Building!
It is hard to even wrap your head around. It stripped the trees and soil off the side of the mountains at that height. Now, that was a very localized event because it was in a narrow bay, but it shows just how much energy can be displaced by a single event.
That is absolutely mind-blowing. It really puts things into perspective. We think we have a handle on nature, and then you hear about a seventeen-hundred-foot wave.
Exactly. And that is why we study these things. Not to be terrified all the time, but to build better, prepare better, and understand the limits of our control.
Well said. I think we have covered a lot of ground today. We have moved from Daniel's nightmare to the physics of subduction zones and the reality of living on the Mediterranean coast. It is a lot to process, but it is fascinating stuff.
It really is. I hope this helps Daniel feel a bit more informed, even if it doesn't necessarily make his dreams any less intense. Knowledge is the best antidote to fear, right?
Usually, yes. Although in this case, the knowledge is pretty intense too! But it is better to know what you are looking at. So, to wrap this up, what would you say are the three main things people should take away from this?
First, understand that a tsunami is not a surfing wave; it is a massive surge of water that lasts for a long time. Second, if you are at the coast and you feel a strong earthquake or see the water recede, do not wait for a siren—get to high ground or go up at least three floors in a sturdy building. And third, know your local geography. Check the tsunami evacuation maps for wherever you live or travel. Most coastal cities have them available online.
Great advice. And I will add one more: if you see those signs in Tel Aviv or anywhere else, take a moment to actually look at where the arrows are pointing. It might save your life one day.
Absolutely. It is all about being aware of your surroundings.
Well, this has been an incredible deep dive. Herman, thanks for all the technical insights. You really have a way of making the physics of disaster sound, well, fascinating.
My pleasure, Corn. I could talk about fluid dynamics and tectonic plates all day, as you well know.
I do know. Believe me, I do. And to our listeners, if you have been enjoying My Weird Prompts and our deep dives into the topics Daniel sends our way, we would really appreciate it if you could leave us a review on your favorite podcast app or on Spotify. It genuinely helps other people find the show and keeps us going.
Yeah, it really does make a difference. We love seeing the feedback and knowing that people are getting something out of these conversations.
For sure. You can find all of our past episodes, including our discussions on earthquake-proofing and digital preparedness, at our website, myweirdprompts.com. We have an RSS feed there too if you want to subscribe directly.
And if you have a weird prompt of your own, something that has been keeping you up at night or just a topic you want us to tear apart, you can find a contact form on the website as well. We would love to hear from you.
Definitely. We are always looking for new rabbit holes to go down. Well, I think that is it for today's episode.
Thanks for listening, everyone. This has been My Weird Prompts.
Stay safe out there, and we will talk to you in the next one. Goodbye!
Bye!
