TESC117: Physical Geology
Peter Selkin
2/9/2016 3:10 AM
Lab 4: Volcano Analogue Models
Based on Fiske, R., and Jackson, E., 1972, Orientation and growth of Hawaiian volcanic rifts - effect of regional structure and
gravitational stresses: Proceedings of the Royal Society of London Series A-Mathematical and Physical Sciences, v. 329, no. 1578, p.
299-326.
In this lab exercise, your group will have a gelatin mold made in more or less the shape of a volcano.
In the lab, you will inject the mold with “magma” (corn syrup) to simulate a volcanic eruption. The
goal of the lab is to illustrate the processes that lead to volcanic eruptions and the geological and
geophysical signals leading up to those eruptions.
1.
You may have some ideas already, either from previous experience or from this class, about
what happens when a volcano erupts. To get at those ideas, imagine what you might see if
you could see through the solid rock that makes up the body of a volcano. In the diagrams
below, illustrate where you think the rising and erupting magma will be.
 The top set of diagrams represent a side view, looking sideways through the
volcano. In the first one, I have drawn the rising magma as a black blob at the
bottom.
 The dotted lines in the successive diagrams show you where the surface of the
volcano was in the first diagram. If you think the surface will change, illustrate that
in the drawings, too, besides drawing the magma.
 The bottom set of diagrams represent a top (map) view, looking down on the
volcano. In the first one, I have overlain a map of a typical volcano, with a circle
outlining the body of the volcano. I expect you to map out where you think the
magma is in each top view as well as in each side view.
 Also, if you think the body of the volcano changes shape from one stage of the
eruption to the next, indicate that by illustrating changes in the circular outline.
2.
Cut a small hole in the plastic wrap on a pegboard. You will insert a syringe tip through this
hole later to move “magma” into the volcano.
TESC117: Physical Geology
Peter Selkin
2/9/2016 3:10 AM
3.
Unmold a gelatin volcano onto the pegboard, so that the volcano sits directly on top of the
hole in the plastic wrap. To unmold the volcano without breaking it, you will need to warm
the gelatin up in a large bowl of hot water until the gelatin moves freely within its mold (spin
it around to see). You do NOT want to break the volcano before unmolding it!
4. Prop the pegboard between two desks. Place a pan below the board to catch any drips.
5. Place four dots of paint on the volcano to represent four GPS stations. These will help you
track the motion of the flanks of the volcano as magma intrudes and the volcano erupts.
6. If you are recording the “eruption,” set up the camera and lights. Arrange two rulers around
the volcano – one horizontal and one vertical – to act as scales in the recording.
7. Fill a syringe with corn syrup. This represents the magma.
Why are we using corn syrup to represent magma?
In what ways is corn syrup similar to magma? In what ways is it different?
Can you comment on what kind of magma the corn syrup best represents?
Why are we using gelatin to represent rock?
In what ways is gelatin similar to rock? In what ways is it different?
8. Insert the syringe into the bottom of the gelatin volcano through the pegboard.
9. If you are filming this, start recording now!
10. Squeeze the syringe to move “magma” into the volcano until it erupts.
 Watch the movement of the simulated magma. Pay particular attention to the
direction(s) of magma flow inside the volcano. Sketch the intrusion in side and top
view for at least three “snapshots” during the experiment (there are four spaces in
case you need to add more due to interesting events). Label each snapshot on the
timeline.
 Also watch the movement of the “GPS stations.” Annotate your diagrams to illustrate
how the GPS stations move during the experiment.
 Consider when you would expect to see rock-cracking (gelatin-cracking)
earthquakes and harmonic tremor (magma movement seismicity) during your
simulated eruption. Annotate your set of diagrams to illustrate these, too.
 Identify any other changes you think are important.
TESC117: Physical Geology
Peter Selkin
2/9/2016 3:10 AM
What was different between your observations and your expectations?
TESC117: Physical Geology
Peter Selkin
2/9/2016 3:10 AM
The images below illustrate lava flows and intrusions at a volcano in France (left) and the eruption of
Mt. St. Helens in 1980 (right). What does this experiment help you explain about these two real
volcanoes? Does it affect where around a volcano a geologist might want to focus monitoring in order
to detect hazardous activity?
M. Petronis et al. 2013.
USGS Prof. Paper 1250