I found a method for using wet wool roving to make multicolored spheres that look like geodes when you cut them open. I thought that it would be a cool and fun activity for kids if you were studying geology, but I also thought it looked a little like a depiction of the layers of the interior of the Earth. We could also look at the interior for the outer gas giant planets in the solar system as well.
For the Earth, I started with warm, soapy water and selected my colors of wool.
For the core, I started with the red, squeezing and rolling.
And blue, green, and white for the exterior.
I had to rinse out all of the soap, continuing to squeeze and roll and left it to dry.
Once it was dry, I used a serrated bread knife to cut it open and display the interior.