• Audience
    Children and families, Primary school, Secondary school
  • Learning stage
    Stage 1, Stage 2, Stage 3, Stage 4
  • Learning area
    Science
  • Type
    Teaching resources

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Have you ever wondered what happens inside a volcano before it erupts? In this hands-on demonstration you will be able to model the reactions and pressure inside a magma chamber using just a few household ingredients.


  • The Earth’s outer layer is divided into plates that move slowly over the semi-molten mantle. This scientific theory, which includes the movement of these plates, is called ‘plate tectonics’. Plate tectonics cause earthquakes and volcanoes. The point where two plates meet is called a plate boundary.
  • A volcano is a mountain built up when lava forces its way upwards from an underground molten rock pool (magma) beneath it. It is like a hole in the earth from which molten rock and gas erupt. They are like giant safety valves that release the pressure that builds up inside the earth.
  • Magma and lava are different! When magma reaches the surface and erupts out of a volcano it becomes lava.

This experiment is an example of a scientific model. A scientific model is something that represents and explains a system or sequence of events without having to see the real thing.

In this example, the model helps us understand the geological processes that are happening inside a volcano without having to get too close to that molten rock!

  1. Water and oil do not mix! Even if you try to shake it up, the oil breaks up into smaller droplets, but does not mix. What causes the water and oil to separate or sit separately in the experiment?
  2. What reaction is happening in this experiment? What chemicals in the Alka-seltzer tablet is causing this reaction?

Materials

For this activity, you will need:

  • Alka-seltzer tablet
  • Cooking oil
  • Water
  • Food colouring
  • Small sealable test-tube or container