Explain that students are going to investigate volcanic processes
by modeling the formation of two types of volcanoes and measuring
the resulting slopes. Procedure
1. Divide students into teams of "Planetary Geologists" and
distribute a couple of large paper plates, protractor, string
and a weight, and some sand, salt, dry rice and kitty litter to
each team. Using a folded piece of stiff paper as a scoop, have
students carefully drop sand from a height of 6 inches into the
center of the paper plate (to simulate material forming a volcanic
cone). Have students record what happens to the sand as they continue
Instruct students on how to connect their protractors, string
and weights to measure angles. Have students measure the slope
angle of the sand volcano they have just created. Record the results
of each team on the board and have students calculate the average.
Challenge students to predict what would happen to the slope angle
of their volcanoes if they used more sand and made the pile higher.
Have them do so and again record and average the results. Discuss.
Next, have students repeat their experiment using salt, rice
and kitty litter. In each case, record and average the results
and discuss. (Note: In all cases, the slope angles will probably
average between 30 and 35 degrees and not be affected by the height
of the cone or the materials used in the Activity.)
2. Show students pictures of cone-shaped volcanoes and have
them measure the slope angles using their protractors. Record,
average and discuss results.
3. Next, lead students in a discussion of shield or basaltic
flow volcanoes and how they are formed. Stress that these volcanoes
do not result from large quantities of material being shot high
into the sky but instead gradually build up when "pahoehoe", a
semi-fluid kind of lava, oozes out of the earth.
Using a clean paper plate, have students simulate this kind
of volcanic formation by slowly pouring chocolate syrup into the
middle of the plate. After a minute or two, have them measure
the slope angle of this volcano. Record and average the results.
Repeat with the butterscotch. (Students will note that the slope
angles here are much gentler, typically only a few degrees.)
4. Show students pictures of volcanoes on Earth (e.g. the Big
Island of Hawaii), but don't characterize them. Have students
measure the slope angles. Record, average and discuss. Ask them
what they conclude about these volcanoes.
5. Show students cross-sections of Olympus Mons. Again have
them measure the slope angle. Record, average and discuss. Tell
them these are characteristic of all volcanoes found on Mars and
ask, as "Planetary Geologists," what they conclude about the nature
of Martian volcanoes.
Based on this, challenge them to draw conclusions about the
presence or absence of plate tectonics on Mars. Challenge them
to suggest why Mars shows no evidence of plate tectonics.
6. Finally, distribute cross-sections of Olympus Mons and the
Hawaiian Islands. Ask them to describe the difference in size.
Challenge younger students to compare the difference in heights
and base widths of these volcanoes. Challenge older students to
estimate by calculation the difference in volume of these volcanoes.
Challenge students to explain why the Martian volcanoes are much
larger than those in the Hawaiian Island chain.
The Hawaiian Islands resulted from a crustal plate slowly moving
over a hot spot and thus, over time, creating a succession or
chain of volcanoes. Due to the absence of plate movements on Mars,
hot spots remained for long periods of time under the same point
in the crust and thus allowed the Martian shield volcanoes to
build to a greater and greater size until Mars' interior cooled.
Indeed, Olympus Mons is the largest extinct volcano in the solar
Connect Turn the discussion back to the theme of plate movements
and relate the Martian volcanoes and their internal sources of heat
to the formation of the Tharsis Bulge. Have students measure the
total height difference between the top of Olympus Mons and the
region of the Pathfinder landing site. Have students compare this
to the difference in height between the top of Mauna Kea in Hawaii
and Mt. Everest to the bottom of the Marianas Trench. Which is the
"lumpier" planet and why?
Study of the canyons and valleys on Mars is an obvious extension
here. Hands-on activities are available from JPL's Mars Exploration
and Public Outreach Program, which is part of NASA's Mars Exploration
For further information contact:
Dr. Cheick Diarra/NASA JPL
Mail Stop 180-401
4800 Oak Grove Drive
Pasadena, CA 91109
Create a 3-dimensional contour map of Tharsis Bulge.
Read about famous volcanic eruptions. Write a "You are There"
article for a publication appropriate to the time in history.
Review angle measurement.