Here you go, your homework assignment for tonight.....
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Subject: How can we make a homemade simulation of a tsunami?
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Dr. Hal Mofjeld, mofjeld@pmel.noaa.gov:
Here's an idea that's very similar to laboratory
models that are often used to study tsunamis.
Water Tank or Trough (a couple of feet long)
Not to scale
Generator Beach
| __________ |
| / \ wave --> |
|_________/ \______________________________|
| /|
| \ / |
| \ <- Hinged plastic plate Fixed Incline-> / |
| \ that pivots up / |
|____\___________________________________________/____|
The Generating Plate simulates the upward motion of the
earth, creating a "bump" in the water. The resulting wave
propagating away toward the beach, or impact area. The
wave builds in height as the water gets shallower toward
the beach (due the the Fixed Incline) and hits the shore.
This will probably work best if the the Generating Plate
is about a foot long and the water is relatively shallow.
It can be moved up rapidly using a strong string attached
to the side away from the pivot, which can be made with
duck tape. The Fixed Incline should be a gentle slope.
more details:
The basic idea behind tsunami simulations is to show the three
stages of tsunami waves: their generation (usually because the
ocean bottom moved up or down, or a landslide hit the water),
the propagation of the waves from the source region to the impact
site (the shallower the water, the slower and more clearer this shows),
and the runup on land (usually with a sloping incline, possibly with
a small model house for effect). There is a trade-off in size between
having the wave model large enough so people can see what's going on
but small enough to be portable.
If the instructions for science projects allow, I'd make the model
out of clear lucite (perhaps coloring the water light blue), 24 inches
long, 6 inches high, and 3 inches wide. The model will work even better
if it can be longer, say an additional 6 or 12 inches in length. I'd
use clear aquarium glue to put the pieces together, so the seams will
hold water.
Some science classes require the use of metric units, like centimeters,
instead of English units. In this case, multiplying the values in
inches by 2.5 will give a reasonable equivalent in centimeters.
The source end can be vertical if the source is a moving bottom
or steeply sloping (one-to-one slope) for a landslide. For the
sloping source-end, the end-piece would be 8.5 inches long. The
moving bottom can be a 2 inch by 6 inch piece of lucite that has
strings attached to each corner (so it can be pulled upward quickly
to start the tsunami wave). There may need to be some thin spacers
attached under the moving bottom to prevent it from forming a strong
suction with the real bottom. You can use a strong plastic bag of
sand or sugar sliding into the water to simulate a landslide.
The impact slope should be a foot long and glued at an angle from
the top where the side walls end diagonally down to the bottom.
This provides a slope of about 27 degree (one-to-two). You'll need
to experiment with the amount of water in the model. I'll say it
would be good to start with one inch (or 2.5 cm) of water to start.
The shallower the water, the slower the waves will travel. If the
water is too deep or moving too fast when it hits the far impact end,
it may splash out of the model. You can lay a short cover shield over
the top of that end if this is a problem. Having paper towels
around is not a bad idea, nor is having a funnel to use when pouring
the water back into the carrying container.
It's a good idea when doing a tsunami demonstration to mention the way
that the way water sloshes back and forth after the first wave hits
the impact site is very much like real tsunamis behave. These tsunamis
slosh back and forth in harbors, so the tsunami danger isn't over
after the first wave.
Reports to me by 9.30am tomorow morning please...
