Tag Archives: geology

How to Simulate the Rock Cycle with Crayons

Rock Cycle

We’ve done two hands-on earth science projects this week – on Monday we made model planet Earths out of clay, and on Thursday we simulated the rock cycle using wax crayons.  Both were great fun, and both reminded me that these kind of projects take more time and effort than I anticipate when I read about other people doing them!

This post is about our experience doing the rock cycle. I hope my usual “what we might do differently next time” section will benefit you!

Before the Activity

We’ve been learning about the rock cycle and different types of rock over the last few weeks. We’ve watched Brainpop videos about weathering and erosion, and discussed how we might simulate weathering if we were using crayons to represent rocks.  I’ve also been strewing rock samples from the collection I bought – just one or two at a time.

Rock Cycle

By now, all of us have Mr Lee’s Rock Cycle Rap stuck in our heads (highly recommended. I was so vociferous in my appreciation of this 6th grade teacher that J(7) asked me “Are you in love with him, Mummy?”). We also enjoyed this Song of the Rocks.

Just before we did the activity we watched the Rock Cycle Brainpop video and looked at pictures of the cycle in National Geographic Kids Everything Rocks and Minerals.

I strewed three rock samples on the table and told the kids one was sedimentary, one metamorphic and one igneous. They examined the rocks and correctly identified the smooth, glassy one as igneous rock Obsidian. (Cue much speculation about whether they could create a Nether Portal.) We didn’t say much more about the rocks – we’ll come back to them when we explore rocks in more detail.

rock cycle
“Weathering” (crayon) rocks

What We Used

  • wax crayons in 3 contrasting colours (we used two of each colour, which made plenty of “rocks”)
  • sharp knife or grater (or pencil sharpener – see below)
  • tin foil (or metal cupcake cases)
  • very hot water
  • rolling pin or heavy book
  • candle (optional)
  • iced water (optional)
  • kitchen paper (optional)

Simulating the rock cycle – What you do

1. Grate or chop the crayons into small pieces, keeping the colours separate.

rock cycle
More weathering

This represents weathering and erosion.

2. Sprinkle a layer of each colour crayon into a small piece of tin foil.

rock cycle
Depositing of (crayon) sediments

This is the laying down of sediments.

Fold up the foil (or put another piece on top) and press down on it very hard.

This simulates the pressure that creates sedimentary rock.

rock cycle

Unwrap your foil and examine your sedimentary rock.

3. Rewrap your squished crayon (sedimentary rock) and heat it by dunking it in very hot water for a few moments, then squish it some more. You could also use other metamorphic crayon-rocks or igneous crayon-rocks to make your metamorphic rock.

rock cycle

This represents heat and extreme pressure inside the Earth, which creates metamorphic rock.

rock cycle

4. Rewrap your heated, squished “metamorphic rock”. This time dunk it in the very hot water for long enough for the crayon to melt completely.  Alternatively, briefly hold your foil packet in a candle flame which will melt your crayon more quickly. (Again, you can also use sedimentary or igneous crayon-rocks to make igneous crayon-rocks.)

rock cycle
Melting (crayon) rocks in hot water to create igneous (crayon) rocks

The melted then cooled crayon represents igneous rock.

rock cycle

We let some of our melted crayons cool slowly, as would happen when magma cools slowly inside the Earth to  create intrusive igneous rocks.  We dunked other melted crayons (in their foil packet) in icy water to represent the fast cooling that takes place when lava cools outside the Earth, creating extrusive igneous rocks.

What We Might Do Differently Next Time

  • Use metal cupcake cases as recommended by Phyllis (whose post I only just found, unfortunately!). This would be much easier than unwrapping the tinfoil packets (we ended up using fresh pieces of tinfoil at each stage, and sometimes our “rocks” broke as they were unwrapped). Plus you’d get to see the melting process.
  • Use a pencil sharpener to “weather” the crayon pieces (another hat tip to Phyllis). This sounds much easier than messing around with knives and graters!
  • I like to involve the children at every stage, but I think next time I’d have a pre-prepared stash of weathered crayon pieces to add to the bits they make. “Weathering” takes a long time!
  • You need to apply a lot of pressure to make sedimentary crayon-rocks. To keep up the pace (especially after all that weathering) I’d have ready some big books the children could put on their foil packets and then stand on.


Momma Owl’s Crayon Rocks

The Crayon Rock Cycle

All Things Beautiful’s Demonstrating the Rock Cycle

rock cycle
You know you’re a homeschooler when your cheese grater looks like this …


rock cycle
… and your rolling pin looks like this.

Crayon Rock Art

Artist Laura Moriarty compiles sculptures inspired by geology textbook illustrations of cut-aways of terrain.  Isn’t this gorgeous?

rock cycle
Rock-cycle inspired art by Laura Moriarty – click the image to see more beautiful sculptures

For more fun educational projects head over to:

Hobbies and Handicrafts at Highhill Homeschool

Homeschool Review and How-To at Hammock Tracks

Collage Friday at Homegrown Learners

Weekly Wrap-Up at Weird Unsocialized Homeschoolers

Science Sunday at Adventures in Mommydom

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