Today, I got to work at the local county fair in the tsunami room. Yes, we have a tsunami room. It’s way cooler than it sounds, I promise.
I pretty much just got to stand around and say “Hello!”. I only said it to people who seemed nice and/or to establish some weird “I’m a designated person for talking to about this particular room and the things inside of it”. We have on display a ponga boat that got washed up on one of the near-by shores. It traveled all the way from Japan. It’s been here two months and it’s owner has yet to speak up. Unfortunately there is a large possibility that it might not ever be claimed, since it is assumed to be tsunami debris from the 2011 Japan Tsunami. It’s a nice talking piece and I clicker-counted ~800 people coming to see it on my 5 hour shift alone!
So there’s this “kiddy corner” that we have set up with a hand cranked tilty-machine that demonstrates how much faster water moves when there is more of it vs. less of it. It also demonstrated that adults turn into little kids when there is a hand crank involved.
The information I explained to the users was that the green (deeper) water moved much faster compared to the blue (shallower) water. You could see that the wave created from the tilt machine reached the other end of the container at different times. I explained that the green waves would represent the bigger faster waves in the open ocean, and that they would reach speeds of up to 500-600 MPH, about the speed of a jetliner. When the wave gets to the shallower water, it slows down to around 25 MPH.
Quite a few adults had this weird association with the colors – that the green water meant ocean water and the blue water meant lake water. So the device could be pretty confusing if you didn’t read the little paper that told you all about the simulation, which happened to this one high school kid and his buddy. There was one kid who was cranking the wheel, stuck in a water-watching-trance. His buddy was on the other side, had read the information, and was quizzing his friend about what was happening. The crank-kid had mostly figured it out, but that damned color association took over. His conclusion from the little lesson was “Oh, so that’s why there’s no tsunami’s in lakes!”
Which I can follow his reasoning…The blue water was shallow water. Blue means lakes. Lakes are shallow. Shallow means no tsunamis!!!
So I decided I’m just going to use this kid as an example and tell you that tsunami’s in lake DO exist!! Lake Tahoe is a great example. There is a ton of research on it’s paleo-tsunami.
There is also this thing called a seiche (pronounced SAYSH), typically defined as an oscillation of a body of water in an enclosed or semi-enclosed basin that varies in period, depending on the physical dimensions of the basin, from a few minutes to several hours, and in height from several centimeters to a few meters. It is caused chiefly by local changes in atmospheric pressure, aided by winds, tidal currents, and occasionally earthquakes.
Basically, it’s this really neat thing that happens when something causes standing waves in a closed body of water, and it can have similar effects as a tsunami, or can even even be caused by one! Here’s a really boring video of a tank of water with waves in it to show you what standing water looks like in it’s basic form.
***By the way, these lake tsunami’s can be caused by volcanoes as well. One of the largest known lake-tsunami wave was recorded at ~850ft in Spirit Lake from Mt. St. Helens. Wikipedia Article
So as you can imagine, this is not a natural hazard that we want our thousands of people and houses who live next to lakes to have to experience.
But hey…Now you have a fancy new word to tell your friends about when you go swimming in the pool.
If you’d like some more information on this kind of occurrence, here is a short article from Earth Magazine about the Great Lake’s seiche history.
No audio, but here is a short computer simulation of a paleo-tsunami in Lake Tahoe.
Here’s a small seiche from Lake Superior (make sure you mute it or turn down your sound, the video is mostly wind)
And here’s what a pool looks like during a 6.8 earthquake.