Io, unlike Earth, has no significant permanent atmosphere (though it does have gases on its surface from place to place and time to time immediately after volcanic eruptions). Therefore, whereas ash and gases from explosive eruptions on Earth rise in billowing plumes and then trail downwind for hundreds to thousands of kilometers, ash and gases on Io rise and then fall back to the surface in semi-ballistic (-parabolic) trajectories. Thus, unlike the extremely asymmetric (elongated downwind) deposits on Earth, explosive volcanic deposits on Io produce roughly symmetric (circular to oval) black, white, yellow, and red rings around their vent locations.
In order to mimic the shape and extent of such deposits accurately, it would be necessary to expel material into an evacuated chamber. This would be a bit impractical for most classroom environments! However, a reasonable approximation can be obtained by ejecting colored powdery material into very still air.
A good, practical model for classroom use should be visually authentic, fairly inexpensive, and use materials that are easily obtainable. In that spirit, our volcano model requires the following materials:
4 plastic travel-size talcum powder bottles
3 small containers of colored powder paint (yellow, black, red)
narrow-ended spoon, such as plastic measuring teaspoon
large white surface, such as a sheet of poster board
safety goggles, such as used in chemistry labs
optional: digital camera
optional: surgical mask (to prevent breathing in of talcum powder)
optional: small table fan
Be sure to do this experiment indoors, to prevent breezes from blowing the powder away.
Remove the caps of three of the four talcum powder bottles and remove approximately half of the powder. Replace with an equal amount of colored powder paint, replace and close cap, and shake vigorously to mix in color. Be sure to rotate powder bottle cap to the open position before "erupting". Place first bottle in center of poster board and draw pencil outline around base of bottle. Don safety goggles (and surgical mask). Be sure there is no air movement (wind or drafts) prior to eruption. Hold bottle firmly to paper and squeeze bottle once, rapidly and firmly, to eject powder upward. Once powder settles, take image (if using camera) to document deposits from first eruption. Switch bottles to use different colors, placing bottle within same pencil outline, and proceed using same procedures outlined above for the first eruption. Repeat as many times as desired. Note how younger deposits obscure older, underlying ones. For a more interesting (and messy) experiment, try following the first experiment with one(s) using mild breezes from a nearby multi-speed table fan. Note how the deposits become asymmetric, elongated downwind, as often occurs with explosive volcanoes on Earth. For a truly authentic experience, print out a large copy (or mosaic) of part of the surface of Io (use one of the regional images from this web site!) to use as the base for your model!
To open a new window with an exercise from the Lunar and Planetary Institute that allows students to build and explore a simple model of this type of volcanism (also found on Io), click on the "LPI Make a Volcano Exercise" link at the left.
Created 30 April 2008