Transformed: How is Igneous Rock Formed?

Author: Janice VanCleave


How is igneous rock formed?


  • Strainer large enough to fit across the bowl
  • Deep bowl
  • 2 sheets of construction paper-1 yellow, 1 blue
  • Food blender (to be used only by an adult)
  • 2 cups (500 ml) tap water
  • 1 teaspoon (15 ml) white school glue
  • Timer
  • 10 to 12 sheets of newspaper
  • Adult helper



  1. Set the strainer across the mouth of the bowl.
  2. Tear each sheet of construction paper into small pieces.
  3. Drop the paper pieces into the blender.
  4. Add the water and glue to the blender.
  5. Ask an adult to turn on the blender and thoroughly mix the paper and water. A thick paper mulch will be produced.
  6. Pour the paper mulch into the strainer over the bowl, and let it sit undisturbed for about 20 minutes.
  7. When 20 minutes have passed, fold the newspaper sheets in half and lay them on the table. Pick up the wet paper mulch with your hand and place it on top of the newspaper.
  8. Allow the paper mulch to dry and solidify. This may take 2 to 3 days.


The dark greenish gray mulch becomes a lumpy solid.


The blending of different-colored paper pieces and water represents the melting of different rocks beneath the surface of the earth due to heat and pressure. This melted rock is called magma. When magma rises to the surface of the earth, it is called lava. Magma and lava cool and solidify to form a type of rock called igneous rock. The drying of the paper mulch represents the cooling of magma or lava to form igneous rock.

Let's Explore

  1. How is sedimentary rock (rock formed by deposits of sediment, or small particles of material deposited by wind, water, or ice) formed from igneous rock? Demonstrate this transformation by repeating the experiment twice, first using yellow and blue paper as in the original experiment, then using white and yellow paper. For ease of handling, work with the paper mulch before it has completely solidified. Break half of the dark mulch into small pieces and press them into a thin layer on top of a stack of newspaper. Make a second layer, using half of the light mulch. Add a third and fourth layer, alternating the dark and light mulches. Allow the model to dry. These two mulches represent two samples of lava. In nature, lava cools and solidifies to form igneous rock. Weathering (the breaking down of rock into smaller pieces by natural processes) causes small particles of igneous rock to break off. The particles build up in layers and eventually form sedimentary rock. Science Fair Hint: Use the model you made to represent the formation of sedimentary rock.
  2. How can metamorphic rock (rock formed from other types of rock by pressure and heat) form from sedimentary rock? Demonstrate this transformation by repeating the previous experiment, except that after you've laid the last layer of mulch, cover it with 2 to 3 sheets of newspaper. In nature, metamorphic rock is formed by pressure applied to rock in solid form. So that you do not have to apply so much pressure, you can work with the layers before they solidify. With a rolling pin, roll back and forth three to four times across the top of the newspaper covering the layers of mulch. Press as hard as you can to try to flatten the layers. Remove the pressed mulch and place it to dry on newspaper. Science Fair Hint: Use the model to represent the formation of metamorphic rock.



Show Time!

  1. Rocks come from other rocks. Igneous rock forms when sedimentary or metamorphic rock melts, then cools. Sedimentary rock is made from sediments of metamorphic or igneous rocks. These sediments form as a result of weathering and are deposited in layers. The layers are compacted and cemented. Metamorphic rock forms when igneous or sedimentary rock is changed by heat and/or pressure. This never-ending process by which rocks change from one type to another is called the rock cycle. Draw and display a diagram similar to the one shown to represent the rock cycle.

Check it Out!


  1. Each rock type can change into either of the other two rock types. Can a rock be changed into a different rock but remain the same type of rock? For example, can granite, an igneous rock, be heated and cooled to form a different kind of igneous rock? Find out and prepare a display showing different possible changes.
  2. 2. Heat and pressure can change granite, an igneous rock, into quartzite, a metamorphic rock. Find out more about the rock cycle. Make diagrams like the one shown, showing the names and types of the rocks and how they change.


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