Eating Earth- Tectonic Plates, Oreos and Milk Way
Amateur geographers can simulate how plates move on the Earth’s surface.
The term tectonics originates from the Greek word “tektõn,” referring to a builder or architect. Plate
tectonics suggests that large features on Earth’s surface, such as continents, ocean basins, and
mountain ranges, result from interactions along the edges of large plates of Earth’s outer shell. The
plates, composed of Earth’s crust, ride on a warmer, softer melted layer of the mantle. This melted
layer, the Upper Mantle, is mostly magma (melted rock) that circulates and causes the plates to move. In
our experiment, the upper cookie will represent the tectonic plates on the crust, the creamy filling the
melted magma in the upper mantle, and the lower cookie the lower mantle.
Choose a cookie. Don’t eat it…yet!
1. First, carefully remove the upper cookie (a “twisting” motion is required).
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Slide the upper cookie over the creamy filling. This motion simulates the movement of a rigid
plate over the softer melted upper mantle.
2. Next, break the upper cookie in half. As you do so, listen to the sound it makes.
3. What sound do you hear? _____________________________________________________
4. What does that breaking represent? ____________________________________________
5. Let’s look at divergent plate boundaries. Divergent means
6. Now push down on the two broken cookie halves and slide them apart. What happens to the creamy
filling? _____________________________________________________________
Draw it:
7. Now let’s look at convergent plate boundaries. Convergent means
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8. Take the two cookie halves and slowly push them toward each other. This simulates when a thick and
heavy continental plate meets a thinner and lighter ocean floor plate. What happens to the filling as the
plates slide together?______________________________________________
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9. What happens to the cookies as they push against each other?__________________________
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Draw it:
10. Take two Milky Ways and push them toward each other. This represents when two heavy continental
plates meet. What happens to the Milky Ways?
______________________________________________________________________________
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Draw it:
11. What do you think this causes in real life?_______________________________________
12. Now let’s look at a transform plate boundary. Try sliding the two cookie pieces laterally past one
another, over the creamy filling. What do you notice about the cookie edges?
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Draw it:
12. What do you think simulates in real life? _______________________________________