How tsunamis work (plus bonus cool illusion)

A new video of the 2001 Japanese tsunami — footage that was just posted in June — got me thinking about tsunamis again. Waves fascinate me.

This video starts showing a drained inlet, and then the leading edge of the tsunami rushing into it, and then filling it, and then overflowing it with a super-tide choked with the wreckage of a city.

The educational value

In the early stages, note how people in this video are mostly casually watching. They clearly have no idea what’s coming, which is very interesting. If they had actually understood how tsunamis work, they would all be sprinting for their lives towards high ground.

I don’t know if I would have realized the danger myself. I’d like to think so, but it’s not clear.

Specifically, did I actually learn enough from the footage of the 2004 Indian Ocean tsunami to be afraid of that drained inlet? Certainly before that disaster, I would have been totally clueless. I really didn’t understand how tsunamis worked, what they would look like. I suppose, like most people, I pictured a particularly huge rolling breaker. Of course, it’s not like that at all. It’s more like an enormous tide. A tide that comes in really fast, and just keeps coming, and coming.

The 2004 tsunami videos were certainly educational, but they may not have been educational enough. Like the people in this video, I may not have realized what was coming. Quite creepy to think about.

Cool optical illusion

This video has an entertaining extra thing: “something” leaps out of the water onto a rooftop at 10:45, perhaps an animal, or a mermaid, or a ghost, and then disappears. When I first saw it, it was a powerful illusion, and I certainly am not the only one to see it that way (there are a bunch of YouTube comments about it).

I had to replay it dozens of times before I finally realized what it actually was. It is almost certainly a spray from a high-pressure tank in the water. If you watch it frame by frame, it begins as a jet at about a 30˚ angle. The narrow origin of the jet moves to the right with the flowing water. Then the jet dissipates as the origin continues to move to the right.