Graham Cracker Geology

Hey, did you feel that?  Sometimes the earth moves under our feet unexpectedly, in a motion that we call an earthquake.  Also, sometimes a mountain that has been sitting there peacefully starts blowing its top all of a sudden.  There is a reason for both of these phenomena, and we can see why these things happen in a sweet experiment.
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What you'll need:

• Graham cracker​s
• Icing
• A plastic knife for spreading the icing
• Red or yellow food coloring (optional)

Experimental Procedure:
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1. If you would like to have realistic colored icing for this experiment, mix in a few drops of red or yellow food coloring to make your icing look like magma (melted rock)
2. Break your graham cracker in half.  It doesn’t have to break perfectly in half - all pieces work.
3. Break one of your half graham crackers in half again.  Now you have one half and two fourths.
4. Spread some icing on the half graham cracker.  Put a fair amount on there - you want to be able to smush it around easily.
5. Put the two fourths of the graham cracker on top of the icing.
6. Put the graham cracker sandwich that you have made down on a solid surface for this next part - it makes things easier to use two hands.
7. Move the two fourths of the graham cracker apart from each other by sliding them on the icing.  This is called divergent movement.  This is what happens under the sea in places like the Marianas Trench.
8. Move the two fourths of the graham cracker together, so that they tent up.  This is called convergent movement.  This is what causes mountains and volcanoes to form.  If you push down on your graham cracker pieces as you are also pushing them together, you might even be able to make the icing seep through the sides or the top of your graham cracker tent.  This represents what happens when a volcano erupts - hot magma bubbles up from underneath the volcano and comes out the top or the sides.  What is melted rock called when it comes out of a volcano? (lava)
9. Move the two fourths of the graham cracker side by side so that the edges are rubbing on each other.  If parts of the graham cracker start to flake off or stick to each other, that is exactly what you want.  This is called transverse movement, and this is what happens when two plates (those things that make up the surface of the Earth) rub together.  They sometimes get stuck on each other, and pieces might break off.  That is what happens during earthquakes!

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What's Happening?:

What you have just made is a simple version of what is happening inside the Earth all the time.  The bottom graham cracker represents the core of the Earth.  The icing represents the magma - melted rock that is in between the core and the tectonic plates.  The top graham cracker pieces represent the tectonic plates.  The tectonic plates (tectonic means things that happen on the surface of the Earth) float around on this melted rock and move in different ways, which we just demonstrated.  When the plates run into each other and push each other up, that is convergence, and it can cause mountains and volcanoes to form.  When the plates run side by side, sometimes they stick and slip.  The slipping is when earthquakes happen.  Of course, there are many other things that happen in the Earth’s crust, too, but this is a good place to start.

Variations and Related Activities:

Making a volcano - We have all made volcanoes with baking soda and vinegar.  But, you can take the process two steps further by making layers of different kinds of lava on your volcano.  Check out another Cool activity to make a volcano with simulated aa and pahoehoe lava.​

Links to more information and activities:

See where the latest earthquakes have happened, and what magnitude they were:

• https://earthquake.usgs.gov/earthquakes/map/

Watch live webcams from Kilauea volcano in Hawai’i:

• https://www.nps.gov/media/webcam/view.htm?id=5B6292AF-D3C2-CF49-C128FA9697DF00B6
• Webcam (U.S. National Park Service)

Subject Tags
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• Earthquakes
• Geology
• ​Volcanoes

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All Earth and Environment Subject Tags:

All
Earthquakes
Geology
Volcanoes