Edible Tectonics Lab
Plate Tectonics is one of geology’s central theories. It explains a wide variety of observations
and natural phenomena, like the distribution of earthquakes and volcanoes throughout the world. It
also explains many of Earth’s processes and physical features. In areas where the Earth’s crust
diverges (moves apart), rift valleys can form on land and mid-ocean ridges can form in the oceans.
Ocean trenches, island arcs, volcanoes and mountain ranges can form in areas where Earth’s crust
converges (moves together). This activity uses a scale model to show hands-on some of these basic
concepts in plate tectonics.
To understand plate tectonics, remember that the lithosphere (crust) is broken up into a number
of slabs or plates of land. Although the plates touch they are not connected to each other and move
independently. Several hypotheses have been offered to explain plate motion. Many geologists think
the asthenosphere (upper mantle) is made of solid rock, but extreme heat and pressure make it flow
like a liquid. Because the lithosphere (crust) rides on top of the asthenosphere, many geologists think
that this flowing rock in the asthenosphere causes plate motion. This natural process is driven by
convection currents in the asthenosphere. Convection currents are caused by heat radiating outward
from Earth’s core. Some of the heat in Earth’s core is left over from Earth’s original formation and
some is released through radioactive decay.
PROCEDURE:
1. Obtain a small Milky Way candy bar and a paper towel.
2. READ THROUGH THE CONCLUSION QUESTIONS BEFORE
PROCEEDING. YOU CAN ANSWER SOME OF THEM AS YOU GO
THROUGH THE FOLLOWING PROCEDURES.
3. Carefully unwrap the candy bar and use your fingernail to make a few cracks across the
middle of the top. The cracked chocolate models the plates of Earth’s crust.
4. Hold the candy bar top facing up, with your left thumb and forefinger holding the sides
of one end and your right thumb and forefinger holding the sides of the other end.
5. Slowly stretch the candy bar, pulling it apart JUST A LITTLE. The chocolate should
separate, exposing the caramel. The exposed caramel represents new volcanic material
that can rise to Earth’s surface. The gooey asthenosphere is represented by the nougat.
6. Slowly push the candy bar back together again. The brittle chocolate may crumble. On
the other hand, “mountain ranges” may form when pieces of chocolate “plates” collide.
Also, one chocolate “plate” may subduct beneath another.
7. Continue to slowly pull the candy bar apart and push it back together again. Do this
until you have a good sense of how plates move.
8. Once you have finished, pull the candy bar completely apart. Look at its exposed
interior and think of the candy bar as a model of Earth’s layers. The top layer of
chocolate represents Earth’s brittle crust or lithosphere, broken into plates. The caramel
represents new volcanic material or magma and the nougat represents the
asthenosphere, where the material is solid, yet still able to flow.
9. After answering the questions AND conclusion, dispose of your model by eating it or
throwing it away. DO NOT EAT YOUR MODEL UNTIL YOUR QUESTIONS
ARE COMPLETED.
10. Make sure to clean your desk area!
Edible Tectonics Lab Questions:
(#’s 1-4 and #8 should be in complete sentences)
1. Describe what you observed with the candy bar when it was pulled apart.
2. What geological features could be seen at a point on Earth where two plates are moving apart
(diverging)?
3. Describe what you observed with the candy bar when it was pushed back together.
4. What geological features could be seen at a point on Earth where two plates collide
(converge)?
5. Describe the consistency (texture) of each of the 3 candy bar layers.
a. Chocolate –
b. Caramel –
c. Nougat –
6. & 7. Draw a profile view (cross-section) of the layers of the candy bar. Label each layer with
its real name AND which layer of Earth it represents. (Hint: the core is not represented.)
8. CONCLUSION: One limitation of this candy bar model is the human effect of your fingers
pulling and pushing-and not the natural geologic processes that cause plate motion. Describe
the natural geologic process that occurs in the mantle which scientist’s think cause the motion
of Earth’s plates. (at least 2 complete sentences)