Participants will learn about the science behind the seiche and how it influences conditions and life
in Lake Champlain
Awareness of the cycles in the lake gives participants an appreciation of seasonal changes in the
lake and how human activities can impact the lake during these changes.
15-20 minutes
Small bowl or basin
Lucite box
Water with food coloring
Vegetable oil
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Content by ECHO Lake Aquarium and Science Center © 2014
Hair dryer (labelled WIND)
Images
Fine dry/wet erase marker
1. Fill the small bowl or basin about half full of plain water.
2. Fill the Lucite box approximately 2/3 with water. Add a line on the box for ease of filling
and so the participants can keep track of where the original interface was. Add food
coloring until the water is sufficiently colored (red or blue).
3. Add approximately one inch of oil.
4. Plug in the hair dryer but keep it off to the side.
Ask participants if they know what a seiche is?
Activity:
Have the participants look at the small bowl or basin sitting on the cart.
 Ask them if the water is moving.
Have one of the participants pick up the bowl/basin and gently slosh the water from side to side
and then set the bowl/basin back down.
 Ask them “Do you think the water in Lake Champlain sloshes like that?”
 What make water move in a lake?
(Participants will probably suggest that wind/ boats/ underwater currents move the water in the
lake.)
Tell the participants that we are going to be looking at how a seiche works. A seiche is a special
kind of wave that happens in lakes and ponds. It is sort of like the sloshing of water in the bowl.
Grasp the two sides of the Lucite box and gently push it from side to side to cause the fluid to slosh.
 Ask the participants what they observe.
 Did all the levels of fluid stop sloshing at the same time?
Explain that a seiche can occur on the surface (surface seiche) or underneath the surface (internal
seiche).
Slosh the Lucite box again.
 Ask the participants if they can see both kinds of seiches.
Have a participant draw a line with the fine marker on the Lucite box at the surface of the yellow
liquid and another one at the interface of the two liquids. Have them draw tick marks (like a ruler
along one side of the Lucite box extending above and below both other lines.
Slosh the Lucite box again so the participants can see what happens now that there are reference
points.
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Content by ECHO Lake Aquarium and Science Center © 2014
Ask the participant what they think will happen to the fluid in the box if we direct a stream of air
from the hair dryer at the top of the fluid in the box.
Place the end of the hair dryer at one end of the box so that the air stream will be directed on the
surface of the fluid in the box. Have the participants observe what happens as you briefly direct the
air stream on the surface. Use the lower setting at first and then turn the hair dryer to high for one
or two seconds. The observations should continue after the dryer is stopped.
The participants should see that the different levels of fluids do not move together and the fluids
gradually go back to their original levels.
Using the images, show the “set-up” of a seiche. Go through the demo again to allow participants to
make more observations.
Further discussion of the layers of the lake in summer and the mixing of the lake can be included in
this activity.
A seiche is a periodic oscillation of some stratum (layer) of a lake. Sustained wind blowing across
the surface of a lake will cause water to pile up in the downwind region of the basin. When the
wind subsides, a current will naturally flow toward the area of lowered surface. The water mass
does not immediately come into equilibrium and the water mass sloshes back and forth like a thin
soup in a bowl passed by a shaky waiter. This phenomenon is a surface seiche.
In a stratified lake, of two or more layers of different densities, the different layers may oscillate
with respect to each other without being apparent on the surface of the lake. This is an internal
seiche. These internal seiches can be significantly greater than surface seiches. During the summer
stratification, the thermocline may oscillate between the less dense epilimnion and the denser
hypolimnion. The thermocline is the layer between the upper and lower layers in which there is a
rapid drop of temperature with depth. These different layers can have very different nutrient and
oxygen contents and, therefore, very different organisms in them.
Seasonal cycles:
In summer, temperate lakes are stratified as described above. As winter approaches, the water
begins to cool at the top where the water contacts the cooler air. As water cools to slightly above
freezing (4 degrees Celsius), because water is most dense at that temperature, it sinks and forces
the water that is less dense towards the surface. This less dense water then cools to 4 degrees and
sinks, forcing more less dense water to the surface. This continues, mixing the water in the lake.
This is called the fall turnover or fall overturn. When the water on the surface cools to zero
degrees, ice may form and the cycle stops because there is a “cover” over the surface. This mixing of
the water also mixes nutrients that were in the lower levels of the lake. In the spring, the ice melts
with the increasing air temperature and the water on the surface warms to 4 degrees Celsius and
then sinks because it is more dense than the water below it. The cycle reverses in what is called the
spring turnover or spring overturn. As the lake continues to warm the summer stratification levels
occur.
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Content by ECHO Lake Aquarium and Science Center © 2014