Request Math Help Regarding Tsunamis

[Quantum]

If a Tsunami were two hundred feet tall how many tons of materials would be needed from a landslide of some sort to create that height?

I have looked for this on the internet and haven't been able to find anything, so your help would be appreciated. Thank you.

 

[Umbran]

We need to know a little more to answer your question:

You give us a height. We need to know the full volume (so height, width, depth - the general shape) and we'd need to know what kind of material it is - a rocky landslide is a lot different from a muddy one.

If you describe to us the scenario you're thinking of, we might be able to help a bit more.

 

[Quantum]

The idea came from watching a show on Tsunamis. They said that there was a danger from an island called Cumbre Vieja of a huge Tsunami several hundered feet tall. The island itself is a volcanic island.

I don't know how to figure out the volume, the gargantuan Tsunami is capable of reaching all the way to Australia and China and Japan as well as capable of hitting the coasts of California and all the way up Alaska.

Here is the wiki on the island itself:

Cumbre Vieja - Wikipedia, the free encyclopedia

Basically, watching that show about this mega Tsunami inspired a scenario for a superhero game I'm running for a few friends in which a terrorist group calling itself Matador (Which stands for Madmen Against Technological Agression Destroying Our Reason & Reality) use a bomb to cause it.

 

[Umbran]

The idea came from watching a show on Tsunamis. They said that there was a danger from an island called Cumbre Vieja of a huge Tsunami several hundered feet tall. The island itself is a volcanic island.

I don't know how to figure out the volume, the gargantuan Tsunami is capable of reaching all the way to Australia and China and Japan as well as capable of hitting the coasts of California and all the way up Alaska.

I'm familiar with Cumbre Vieja, and the threat from the island. However, there's a bit you seem to have missed.

Cumbre Vieja is in the Canary Islands. In the Atlantic Ocean. The collapse of the the island threatens things with Atlantic coastlines. The places you mention are all on the Pacific, and not threatened by this island.

The article you linked to actually gives you the answer - approximately 500 km3 (5 x 10^11 m3) of rock, with an estimated mass 1.5 x 10^15 kg.

1.5 x 10^15 kg is roughly 1.65 x 10^12 tons. That's 1.65 trillion tons - as if that number has meaning to humans.

However, note that it is not the mass (or weight) per se, that is the issue. It is how large a volume of water is moved how quickly - we are talking about moving 110 cubic miles (110 cubes of 1 mile per side) of water in mere moments.

The simplest way to make this happen is to have your supervillains set off Cumbre Vieja, or arrange for a massive earthquake in the Pacific, if you want to threaten Japan and such.

 

[Quantum]

Cumbre Vieja is in the Canary Islands

Thank you. I did read that in the Wiki. The point I was trying to make is that watching that show on the island was the inspiration for the scenario.

Another question I wanted to ask, but unfortunately didn't think to include, is how do we figure out how far inland would a Tsunami go in if it were two hundred feet tall?

 

[Umbran]

Another question I wanted to ask, but unfortunately didn't think to include, is how do we figure out how far inland would a Tsunami go in if it were two hundred feet tall?

That depends both upon the wave (they aren't all the same), and the shoreline. There isn't a simple formula for it - the models are pretty complex.

If the tsunami hits a cliff wall higher than it is, it doesn't go inland at all. If it hits a shore that is a very long, shallow slope, it can travel a very great distance indeed. Even recent non-mega tsunamis have gone 3 to six kilometers inland in some regions of Southeast Asia.

In game terms, I'd suggest just telling the players what major cities will be wiped off the coasts. They'll get the idea

 

[Rackhir]

I saw the same show and got the idea to use a chunk of Thronehold (The island capital of Eberron) to wipe out an aberration army, in Shilsen's SH.

But I agree it's best off just simply handwaving it and simply declare what effect it will have.

 

[Dannyalcatraz]

It would also depend on the body of water- there's evidence that volcanic activity in the Pacific Northwest has caused tsunami-like waves in some of the lakes and rivers. The water, being constrained on both sides by hills and/or mountains, has nowhere to go but up and away...

 

[Crothian]

One thing that might help, and I wish I had a link but maybe someone else does, is a look on raising ocean levels to cities near them. In a geology class I took last year the professor showed us a map on line of Houston, Texas and then was able to raise the water levels by a foot, then two feet, then three feet, etc and the map would show what areas of the city would get flooded by just a little raise in the water level.

 

[Theo R Cwithin]

Re: DannayA's post: I understand that calving glaciers in fjords can kick up huge waves for the same reason. They can be very high, but they're very limited in geographical extent & quickly dwindle away when they hit open sea.

Re: Crotian's post -- Here's an interactive flood map, but it only goes up to +14m.