Metamorphic Rock: Melting Rocks

Suggested Grades



Students will observe and gain a better understanding of the metamorphosing power of heat.


  • 2 cups mini-marshmallows
  • 1 cup choc chips
  • smooth peanut butter
  • waxed paper
  • hot plate
  • mixing bowl
  • mixing spoon


  • Mix mini-marshmallows and chocolate chips in a bowl. Add just enough peanut butter so so the mixture clumps together.
  • Ask each student to grab a handful of the mixture and make a rock.
  • Place “rocks” on waxed paper. Explain to students that right now, the rocks resemble sedimentary rocks. The marshmallows and the chocolate chips could be seen as sediments and the peanut butter could be seen as a mineral that sticks the sediments together.
  • Place a few of the “rocks” on the pan and heat them over low heat. When the marshmallows melt, give each student a spoonful of the new “rocks”.
  • Explain to the students that these new rocks resemble metamorphic rock. The sedimentary rock changed its form and structure because of the heat.