Hands On: Candy Rock Cycle

Big Idea:

Rocks are not permanent. Earth is a giant recycling machine that uses heat, pressure, weathering, and time to transform one type of rock into another over and over again.

Materials:

3 to 4 colors of Starburst candies, unwrapped
Safety scissors or a butter knife
Wax paper or a plastic sandwich bag
A microwave-safe plate (adult supervision required for microwave step)
Heavy books or strong hands for pressing

What to Do:

Step 1: Make Sedimentary Rock

Use the scissors or butter knife to cut the Starbursts into small jagged bits. These are your sediments from weathering and erosion. Pile the different colors together on the wax paper. Press them firmly together with your hands or under a heavy book until they just stick together. You should still see the individual grains and color layers. "Sedimentary rock forms when layers of sediment are pressed together over time."

Step 2: Make Metamorphic Rock

Take your sedimentary candy and squeeze it harder, twist and press without letting it melt. "Deep underground, heat and pressure change rock without melting it completely. The layers twist and compress into metamorphic rock." The colors will start to blend but you can still see evidence of the original layers.

Step 3: Make Igneous Rock

Place the metamorphic candy on the microwave-safe plate. Microwave for 5 to 8 seconds, just enough to soften and flow slightly (adult supervision required). Let it cool and harden. "When rock melts completely and then hardens again, it becomes igneous rock. The word igneous comes from the Latin word for fire."

Step 4: Start the Cycle Again

Cut the cooled igneous candy back into small bits. "Weathering breaks igneous rock back into sediments, and the whole cycle begins again."

What's Really Happening (Caregiver Explanation):

The rock cycle has no beginning and no end, rock is constantly being recycled through Earth's systems over millions of years. The same atoms that made up ancient mountains have been through the cycle many times. The heat source driving metamorphic and igneous processes is Earth's internal heat from radioactive decay and the original heat of formation. Weathering and erosion at the surface are driven by the Sun's energy through wind, water, and ice. In this sense, the rock cycle connects Earth's internal engine to its surface systems.

Digging Deeper:

Research the difference between granite and obsidian. Both are igneous rocks, but granite has visible crystals while obsidian does not. What does that tell you about how each one formed? The key is how quickly the magma cooled. Then look up intrusive vs. extrusive igneous rock and explain why crystal size is a clue a geologist uses to read a rock's history.