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Model the Rock Cycle with Crayons

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Summary

Active Time
20-30 minutes
Total Project Time
20-30 minutes
Key Concepts
Rock cycle
Credits
Ben Finio, PhD, Science Buddies
Crayon Rock Cycle

Introduction

Use crayons to model the rock cycle in this fun activity! You will make colorful sedimentary, metamorphic, and igneous "rocks" from crayon shavings.

This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Materials

  • Crayons
  • Potato peeler, paring knife, or cheese grater
  • Aluminum foil
  • Frying pan
  • Tongs or oven mitts
  • Toothpick
  • Small bowls
  • Ice water
    Materials for crayon rock cycle activity

Prep Work

  1. Peel the paper wrappers off your crayons.

Instructions

  1. With adult supervision, use a potato peeler, knife, or cheese grater to make crayon shavings from at least two different color crayons. Keep different colors separated in different bowls.

    Different color crayon shavings in two different bowls.
  2. Pile the shavings into layers on a sheet of aluminum foil, one color per layer.

    Crayon shavings in a layered pile on aluminum foil.
  3. Fold the aluminum foil over on top of the pile.

    Aluminum foil folded in half over the pile of crayon shavings.
  4. Press down as hard as you can with the bottom of the frying pan for at least one minute. You can also put the aluminum foil on the floor and stand on it, or ask an adult for help. The harder you press, the better.

    Frying pan pressed down on top of the aluminum foil.
  5. Remove the pan and unfold the aluminum foil.

    Crayon shavings on aluminum foil compressed into flat layers, forming a sedimentary
  6. Carefully peel the aluminum foil away from the crayon shavings and remove the pile. This is your sedimentary "rock."
    Think about:
    What does the rock look like? How did the individual crayon shaving pieces combine to form a single rock?

    The crayon sedimentary rock removed from the aluminum foil. The two colors of crayon shavings form two mostly distinct layers.
  7. Return your sedimentary rock to the aluminum foil. Put the aluminum foil in the frying pan, press it down flat, and heat it on the stove over medium-low heat.

    Sedimentary crayon rock  melting on the stove.
  8. Using oven mitts or tongs, remove the aluminum foil from the pan when the crayon rock has just melted completely. Watch as it cools, but do not touch the melted crayon.

    Melted crayons on aluminum foil cooling off on the counter.
  9. Carefully peel the melted crayons from the aluminum foil. This is your metamorphic rock.
    Think about:
    Examine the rock carefully. What are the differences between this rock and your sedimentary rock?

    Pile of crayon shavings melted together, with swirls of two different colors.
  10. Prepare a bowl of ice water.
  11. Put the "rock" back on the aluminum foil and return it to the stove over medium-low heat. This time, when the crayons melt, stir them with a toothpick until the colors are mixed completely.

    Melted crayons on the stove being stirred with a toothpick.
  12. Using tongs or oven mitts, quickly lift the aluminum foil and pour the melted crayons into the bowl of ice water.

    Melted crayons being poured into a bowl of ice water.
  13. Remove a chunk of solidified crayon from the bowl. This is your igneous rock.
    Think about:
    How is this rock different from your sedimentary and metamorphic rocks?

    A twisted blob of solidified wax representing an igneous rock.
  14. If you have enough crayons, repeat steps 1–6 to make another sedimentary rock, and steps 1–9 to make another metamorphic rock. This way you will have one of each type of rock, and you can compare them side-by-side.
    Think about:
    What are the similarities and differences between your different types of rock?

Cleanup

You can melt any remaining crayon shavings and use your rocks to form new crayons!

What Happened?

When you pressed down on the pile of crayon shavings, you exerted a lot of pressure that smashed them together into one solid piece with multiple layers. This "sedimentary rock" might have been crumbly and fragile, especially around the edges. When you melted the sedimentary rock on the stove, the different colors started to swirl together, but different colors were still visible. When it cooled, the "metamorphic rock" was much stronger and less crumbly than the sedimentary rock. Finally, when you melted the metamorphic rock again and stirred it with a toothpick, the colors mixed completely (for example, in the photos above, red and yellow combine to make orange). When you poured the melted crayon into a bowl of ice water, it cooled rapidly and solidified, forming an "igneous rock." The resulting shape may have air bubbles or pockets in it because of the way it cooled. Read the Digging Deeper section to learn more about the rock cycle and different types of rocks.

Digging Deeper

In this activity, you used crayons to model how different types of rocks are formed on the Earth's surface and inside the Earth. Over thousands or millions of years, sand, dust, and dirt will form different layers on the ground. Eventually these layers get pressed together and compacted to form sedimentary rocks. As these rocks get moved even deeper underground due to the motion of the Earth's crust (plate tectonics, see link in Additional Resources section), they are exposed to even higher amounts of heat and pressure, turning them into metamorphic rocks. Eventually it gets so hot that the rocks melt completely. This melted rock is called magma. When magma cools and solidifies (for example, when it erupts from a volcano and is exposed to air or water), it forms igneous rocks. The links in the Additional Resources section have more information and diagrams illustrating the rock cycle.

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For Further Exploration

  • Can you figure out how to turn an igneous or metamorphic rock back into a sedimentary rock? What natural processes do you think could make this happen with real rocks?

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