It’s a Hard Knock Rock Life: 8th Graders Recreate Rock Cycles with Recycled Crayons

If you’re a parent, you’ve likely had a box or two of broken Crayons in your home that eventually get tossed but have you ever received an all-call request for them? Middle School Science instructor Ms. Coakley '05 has found a way to give new life to dozens of the little colorful waxy sticks. Coakley’s 8th grade class is using them for a lab that recreates and visualizes each step of the rock cycle—from magma to igneous, sedimentary and metamorphic. The current rock unit focuses on how the Earth’s surface changes over time, with a major focus on the rock cycle.

“A lot of [other] labs look at existing rocks and compare the types of rocks,” said Coakley. “This is useful—and we will do some of that in future lessons—but I like that this lab allows us to model the processes that change rocks from one type to another rather than just viewing the end result of each process. It’s not a perfect model, but it does allow students to recreate some version of each step in the rock cycle and then think about how it relates to the actual processes.”

Divided into teams of three to four, students gathered around each table, equipped with a toolkit of foil sheets, a small grater (like a cheese grater), several different colors of Crayons, a heavy textbook, a hot iron and a hot plate. 

First, students carefully grated the crayons, creating small piles of shavings in multiple colors, which symbolized sediments. Next, students layered the shavings on top of the piece of foil, and folded the foil in half to cover up the shavings. They placed a heavy textbook on top of the foil and pressed down firmly to add more weight. They opened the foil and examined the changing appearance of the flat “rock.” Next, they put the flat Crayon rock back inside the foil and used a hot iron to apply heat, and then added the weight of the textbook once again to apply more pressure. With each step, the students documented their observations.

“After you apply heat and pressure, what kind of rock does it become?” Ms. Coakley asked a group of students as the smell of melted Crayons filled the air.

“Metamorphic,” someone answered out loud.

Jacob Marks ’29 and his lab partners were ready to move on to the next phase of the rock cycle. The instruction sheet laying on the table in front of them directed them to grab a new piece of foil and create a boat shape about the size of two hands placed side by side. They added layers of unmelted Crayon shavings inside, and placed the foil boat on top of a hot plate. This time, the students did not apply any pressure on top.

“We’re creating an igneous rock instead of a metamorphic rock,” explained Marks.

Ms. Coakley confirmed Marks’ observations while talking to another table of students nearby. She told them the melting process turns the rock into magma, and when it cools again they will have an igneous rock. As students were cleaning up their stations, they reflected on what they noticed.

“We learned a lot of things can change over time based on temperature or pressure,” said Emory Laws ’29.