I got the lesson started with this book about rocks.
We learned that metamorphic rocks are made from existing rocks. They are rocks that go through metamorphosis or change in form to create a new rock. Through heat and pressure, existing rock is metamorphosized into new rock.
The Very Hungry Caterpillar, or any book about the life cycle of a butterfly, works well for illustrating the process of metamorphosis for young children.
We started by pouring a variety of chocolates (milk duds, chocolate chips, white chocolate chips, buttterscotch chips, and reeses pieces) into a large bowl. We imagined that the candies were different kinds of rocks.
We used a microwave to simulate heat and we placed a large heavy bowl down hard on the mixture to simulate pressure. I microwaved the mixture about 3 minutes at a time. After each 3 minute interval we pulled the bowl off the top, looked at how the mixture had changed, and stirred it. I continued to microwave the mixture until it was melted and smooth.
This picture was taken after the first 3 minutes. The time it takes to completely melt the mixture will vary based on how much chocolate you put in the bowl and the power level on your microwave.
After the mixture was all melted, we covered it and placed it in the refrigerator to cool. We talked about how metamorphic rock was formed by be heated up, pressurized, and then cooled.
Once cooled, I used a small knife to break the mixture up so that it looked like chunks of rock. Helpful Tip: After you melt the mixture, you may want to move it to a baking dish so that it is not too thick. The thicker the mixture is the harder it is to break up after it cools. You want it thick enough to look like rock chunks when you break it up though. I had to microwave the cooled mixture for just over a minute so that it broke up easier. For more rock fun, click here.