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Underwater Volcano Experiment

For a fun way to learn about water density as well as underwater volcanoes, try this underwater volcano experiment. You only need a few household items to create this simple science experiment!

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Underwater Volcano Science Experiment

Parents and educators can demonstrate the science of density with this experiment. It’s also a fun demonstration for kids on how an underwater volcano works.

You only need a few household items – food coloring, large vase or container and a smaller glass cup.

Science Experiment for an Underwater Volcano

What Is The Science?

Not only will kids learn about underwater volcanoes, but they will also learn about density using hot and cold water. The temperature of water affects its density. Cold water is more dense than hot water. When you place the glass of colored hot water inside a container of cold water, the hot water will quickly rise because it has a lower density.

The molecules in hot water move around more quickly and bounce off of each other, creating more space in between them. Because of this, hot water weighs less than cold water and it will rise to the top when hot and cold water is mixed together.

The majority of volcano eruptions in the world occur underwater. The rising magma can also create islands above the surface of the ocean. This experiment is a fun way to see how it might look as hot magma rises from the surface of the earth under the water.

See more volcano experiments:

Watch the Video Tutorial

Follow-up Experiments

Try this experiment again but change some of the variables to see what happens. Try different colors for the dye or different temperatures for the water. Try cold water in the small glass to see what happens. Or try warm water in the large vase and cold water in the small glass.

Underwater Volcano Science Experiment

Supplies Needed

  • Liquid food coloring
  • Large glass vase or jar
  • 2 small glasses or small dessert glasses – we used 2 but you can also just use 1
  • Hot and cold water

How to Do an Underwater Volcano Experiment

1. Fill a large glass vase with cold water.

Large Vase

Leave a little bit of room at the top of the vase so that it doesn’t overflow when the small glass is placed inside.

Add Cold Water into Large Jar

2. Add a few drops of food coloring to the bottom of a small glass.

Add Food Coloring to Small Cup

3. Fill the small glass with hot water.

Boil water and then let it cool a little bit before pouring into the small glass.

NoteAdults to do this part. Let the water cool a little bit before touching (or use gloves) so that the glass is not hot to the touch.

Add Hot Water to Cup

4. Carefully place the small glass of colored water inside the large vase of cold water.

Before placing into the large vase, add another small glass on top of the small glass with red hot water. This is so that the red water does not come out until it’s placed inside the large vase. Then, quickly remove the top small glass.

Alternatively, you can quickly place the small glass inside and remove your hand as quickly as possible.

In the example below, there is a smaller glass on top of the glass with the red, hot water inside.

Add Small Jar into Large Jar

5. Quickly remove your hand and/or extra glass and watch the colored hot water rise!

Add Smaller Cup into Jar

This is an easy experiment to do to show kids how an underwater volcano works!

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