Home Experiment: Underwater Volcano

You will need:

  • Small bottle
  • Large glass jar
  • Scissors
  • Hot and cold water
  • Red food colouring
  • String

What to do:

  1. Cut a long piece of string.
  2. Tie the string firmly around the neck of the bottle.
  3. Pour cold water into the large glass jar until it is about three quarters full.
  4. Fill the small bottle with hot water. Add food colouring to make the water bright red.
  5. Hold the small bottle by the loop of string. Lower it gently into the jar with cold water.
  6. The hot red water rises from the bottle like smoke from an erupting volcano.


Hot water is less dense than cold water and always rises to the surface. Cold water floats underneath. This is the reason why the hot red water rises to the surface, making your experiment look like an erupting volcano.

There are deep holes in the ocean floor. Water, heated by rocks deep in the Earth’s crust shoots out of these holes and rises to the surface of the sea. Divers have discovered strange sea creatures that live around these hot-water holes.

You can watch this experiment as a video here:


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