Geology Activities with Marshmallows 

These geology activities with marshmallows demonstrates how crystals grow

These geology activities demonstrate how crystals grow in magma. Igneous rocks like obsidian form with out crystallization. While deep underground in plutons molten rock slowly crystallizes as it cools. The rocks in plutons have large crystals. In this activity you will see how magma changes as it crystallizes.

Geology activities with marshmallows 

Geology activities, Marshmallow crystals, Photo by Myrna Martin


  • Bag of colored miniature marshmallows
  • Box of colored toothpicks
  • String


  1. Lay all the miniature marshmallows and toothpicks in random order on the table.
  2. This represents glassy igneous rocks such as pumice and obsidian.
  3. Glassy igneous rocks cool and harden without crystals.
  4. Stick toothpicks into three marshmallows to form a triangle.
  5. Continue joining marshmallows together until you have about 20 triangles.
  6. The triangles represent microscopic crystals that have formed in the magma. The rest of the marshmallows and toothpicks represent magma that has not crystallized.
  7. Basalt and andesite in lava flows have microscopic crystals.
  8. Connect all the triangles into one large crystal.
  9. This represent crystals that have cooled deep underground in plutons.
  10. In general, the larger the crystal the deeper the rock cooled underground.

More Links to Science Activities

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Pizza of the Earth - Earth Science Activities Learn the major areas inside the Earth while having a pizza for dinner in this good to eat science activity. 

Granite Cookies Kids Science Activities Create granite cookies that resemble rocks that form the base of all the continents in this good to eat and fun activity.

Shield Volcano - Volcano Activities Create a shield volcano out of clay like the Hawaiian Islands in this hands on science activity.

Marshmallow Crystals - Geology Activities Learn the difference between glassy, microscopic crystals and large crystals in this fun and good to eat science project.

Science Activities Fun and easy activities that demonstrating science concepts can be found on this page

Home Page  The Science Site contains information on our planet, volcanoes, science projects, earthquakes and much more.


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