How to Make a LEGO Volcano that Erupts!

Learn how to make a LEGO Volcano that erupts! In this awesome baking soda and vinegar science experiment, children will love building a volcano with LEGO blocks and watching it explode.


Making a volcano is another classic science experiment you do in grade school. Usually, you construct a volcano out of paper mache, but that’s messy. 

What’s not messy? LEGO!

There is no need to get sticky glue everywhere for this fun erupting volcano experiment. You just need lots of LEGO pieces to build the volcano and the rest is science!

How to Make a LEGO Volcano



1. Place the plastic cup near the center of the baseplate.

2. Start building around the plastic cup with LEGO bricks.

3. Continue building until you form a volcano (it doesn’t have to be perfect!).


4. Pour 3-4 tablespoons of baking soda, 1 tablespoon of dish soap, and 5 drops of food coloring in the plastic cup.

5. Add about ¼ cup of water and mix to form a slurry.

6. Move the volcano outdoors where there is sand, pebble, or dirt. If you can’t go outdoors, then I recommend putting the volcano on a baking sheet to catch all the “lava.”

7. Slowly pour vinegar into the plastic cup, and then watch the volcano erupt!

After the foam subsides, you can pour more vinegar in the cup and make the volcano erupt again! And since the plastic cup is removable, you can always take it out when it’s full, dump out the liquid, and redo the whole experiment again. Trust me, your kids will want to.

And for clean up, we chose to use water guns! Just remove the cup and let your kids go wild shooting the LEGO volcano clean with water guns. Super fun and less work for mommy!

The Science Behind the LEGO Volcano

As baking soda (sodium bicarbonate) mixes with vinegar, carbon dioxide and water are created. That’s why you can hear the fizzing sounds coming out of the “lava.” The addition of the dish soap creates even more bubbles and foam, making the “lava” thicker and more realistic looking.

Here are some experiments for the kids to try:

  • Try adding more or less baking soda in the plastic cup. Did the eruption become more violent or less?
  • Try adding more dish soap to the baking soda slurry. Did it make your eruption foamier?
  • Try mixing vinegar with dish soap, water, and food coloring in the plastic cup. Then add baking soda to make the eruption. Did the chemical reaction occur right away as it did with pouring the vinegar in the baking soda slurry?
  • Try making tracks in your volcano. Did the “lava” follow the flow of your tracks down the volcano?
  • For some sensory play, your child can stick his or her hands in the “lava.” What does it feel like? (Just make sure to wash his or her hands right away to avoid the food coloring from staining his or her hands.)

Final Thoughts on the LEGO Volcano

Before you jump into the LEGO volcano experiment, do allot quite a bit of time. It took my son and I about 1 hour to build the volcano itself. 

Also, the volcano took a lot of pieces to build, and by the end, we were trying to find every little piece we had in our LEGO container to make it more like a volcano with slopes instead of sharp cliffs. Thank goodness we got the LEGO creative brick box that morning so we could finish building.

If your kid loves volcanos and LEGO, check out the LEGO City Volcano Exploration Base.

LEGO even has the perfect book to go with this experiment so that your little one can tag along as LEGO minifigures explore fiery volcanos and other forces of nature.

I hope your child loved building the volcano and making it erupt! You may have to save this one for a future science fair.


Want this activity in an easy-to-print file? I have compiled 5 super fun LEGO STEM activities for kids in a printable PDF.

Each activity includes a list of supplies, step-by-step directions, an explanation of the science behind the activity, and different extensions based on the science concepts.

It includes:

  • Balloon-Powered LEGO Cars
  • LEGO Zip Line
  • Penny LEGO Boat Challenge
  • LEGO Volcano
  • LEGO Plinko Board

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