step into my classroom: rock cycle lab

In 8th grade earth science we are working our way through the geology unit. We began with a discussion of origins and debated Creation theories, the age of the Earth, and other controversial issues. Last week we completed our study of minerals and now we are learning about the various types of rocks. I like to kick off my rocks unit with a very hands on activity in which the students model the various processes (weathering, erosion, compaction, cementation, melting, cooling) of the rock cycle using crayons. It may sound like a rather elementary lab, but the reality is I would not be able to do this with a classroom full of 8-year-olds!

this was a challenge with 26 students...

We begin with a solid crayon, which represents an igneous rock. Igneous rocks are formed by molten material called magma, which can form below Earth's surface or above (in which case its called lava).

We model the process of weathering and erosion by using a plastic knife to shave pieces off the crayon and trade shavings with another student. This part takes the longest, but it also takes a long time in real life for wind and water to break down large rocks and carry the pieces to another location.

crayon shavings beginning to melt

To represent the formation of a sedimentary rock we squish the crayon shavings together and apply pressure, creating a delicate crayon "cookie". Cementation and compaction creates sedimentary rocks, some of which are rather fragile as they are just a bunch of little pieces glued together.

what do you see?

Now comes the fun part! Using hot water and a little foil boat we partially melt the crayon cookie and the colors begin to swirl together. When a metamorphic rock forms, the heat and pressure will realign the minerals inside, sometimes causing the crystals to form bands, or foliations.

 

metamorphic rock

some groups waited a long time for something to happen

Let the cookie completely melt and turn to liquid wax to complete the cycle. When it cools down, the crayon magma will harden into a yucky brown chunk, just like a lava flow will harden into an igneous rock.

igneous rock

ooOOOoo

My fellow science nerdish friend and teacher Michele was able to assist me during this lab. It was so helpful to have an extra set of eyes and hands in the room to provide extra help for the students, and to also get some pictures while I taught. It's been two years since I've had a regular teacher's aid, so it was really nice to have Michele for the day.

filling in the steps to the rock cycle