Pass around several sedimentary rocks, igneous rocks, and metamorphic rocks for the class to observe. Have them work in groups to describe the characteristics of each rock type, and place those characteristics into a graphic organizer of their choice. For example, they might find that sedimentary rocks are made up of distinct pieces, that metamorphic rocks contain crystals or swirls, and that igneous rocks seem more uniform than the other two rock types. Discuss their answers with the class.
Crayon Rock Cycle
To show students how the rock cycle proceeds, hand out crayons and crayon sharpeners (or blunt knives, for older students). Show them how to create piles of crayon shavings. Then have each group take a pile of shavings, wrap them inside of a pocket of aluminum foil, and pound them with the edge of a textbook. When they unwrap the shavings, they will likely find one solid piece made up of various colors. Explain that sedimentary rocks are made when pieces of rock are packed tightly together to form one rock.
Then hand out foam cups of hot water and have them place the created rock on a piece of foil in the water. The original rock should start to melt. Before the colors start running into each other, instruct students to remove the foil from the water. Explain that metamorphic rocks are created when other rocks are subjected to heat and pressure. Then have them replace the foil and rock in the hot water and wait until the colors run into each other and are almost completely liquid. Explain that igneous rocks are formed when rocks are subjected to very intense heat and pressure.
The Most Delicious Rock Cycle Activity
Have students brainstorm ideas about baked foods that are created just like the three phases of the rock cycle. For example, Rice Krispy treats or granola bars can represent sedimentary rocks, fudge or chocolate chip cookies (the dough with the chips) can represent igneous rocks, and a cake can represent metamorphic rocks. If you have access to kitchen facilities, you can even make some of these treats with your class!