I bet you never thought to pair your LEGO basic blocks with a cool kitchen science chemical reaction? I didn’t either until my son suggested we build a LEGO volcano one morning from basic bricks. This is the perfect STEM experiment for hands-on learning that will keep your kids busy anytime! No need to have a specific LEGO set. We have tons of unique LEGO activities for you to enjoy!

Build An Erupting LEGO Volcano

There’s nothing better than baking soda and vinegar experiments to explore chemical reactions! It is one of our go-to science experiments and we have loads of fun variations. This time for LEGO week, we made a LEGO volcano.

Build your own LEGO volcano! I am not a master builder and my son is only 5.  But we had a great time figuring out together how to make this LEGO volcano actually look like a volcano. We sorted through all our colors for black and brown bricks. We highlighted our volcano with red and orange bricks for lava. 

Kids of all ages will love working with you independently with friends and siblings to build a volcano model!

I put a test tube from our science kit in the middle of the LEGO volcano. Any narrow jar or bottle you can build around will work. Try a spice jar or mini water bottle. I showed him how we could start the bricks out wide and taper them in towards the test tube to form a volcano.

We added all the brown and black pieces we could find to make our LEGO volcano look mountainous and “bumpy”. 

How Does A Volcano Erupt?

Well, it’s not because of baking soda and vinegar! But it is due to escaping gasses and pressure. But in our homemade volcano below, we use a baking soda and vinegar chemical reaction to mimic the gas produced in a volcano. Baking soda and vinegar are the best ingredients for a homemade volcano!

The chemical reaction produces a gas (read more about how it works further on) which pushes the liquid up and out of the container. This is similar to an actual volcano where gas builds up underneath the earth’s surface and forces the magma up through the hole in the volcano, causing an eruption.

Some volcanoes erupt with an explosive spray of lava and ash, whereas some, like the active volcano in Hawaii, the lava flows out the opening. It all depends on the shape and the opening! The more confined space, the more explosive the eruption.

Our sandbox volcano is another excellent example of an explosive volcano, or example our mentos and coke experiment.

Read more about the science behind baking soda and vinegar experiments.

Learn More About Volcanos!

You can read more about types of volcanoes here with our homemade salt dough volcano experiment. This volcano activity is another great way to occupy time and extend the classic baking soda and vinegar reaction.

Also check out these interesting volcano facts for kids. Plus, a free printable volcano activity pack for you to download and use.

How Does A Baking Soda And Vinegar Reaction Work?

Chemistry is all about states of matter, including liquids, solids, and gases. A chemical reaction occurs between two or more substances that change and form a new substance.

In this case, you have an acid (liquid: vinegar) and a base (solid: baking soda), reacting to make a gas called carbon dioxide. Learn more about acids and bases. The gas is what produces the eruption, you can see.

The carbon dioxide escapes the mixture in the form of bubbles. You can even hear them if you listen closely. The bubbles are heavier than air, so the carbon dioxide collects at the surface of the salt dough volcano or overflows depending on how much baking soda and vinegar you add.

For our erupting volcano, dish soap is added to collect the gas and form bubbles that give it a more robust volcano lava-like flow down the side! That equals more fun! You don’t have to add dish soap, but it’s worth it.

Get your free printable brick building challenges!

DIY LEGO Volcano


  • Baseplate
  • Small bottle (preferably with a narrow opening)
  • LEGO bricks
  • Baking soda
  • Vinegar
  • Dish soap
  • Food coloring
  • Bin, tray, or container to set the baseplate in to catch the overflow.


STEP 1: Build a volcano model around your chosen container!

TIP: Leave some cracks or gaps around the LEGO Volcano to let the lava flow through!

STEP 2: Fill the container inside the LEGO Volcano with baking soda. I filled our container about 2/3 full.

STEP 3: Mix vinegar with red food coloring if desired. I ended up having to use apple cider vinegar. Usually, our experiments just include baking soda and vinegar. This time I squeezed a few drops of dish soap into the vinegar and gently stirred.

TIP: Add dish soap to the vinegar mixture to make for a much frothier eruption with fun bubbles too!

STEP 4. Add the vinegar to the baking soda.

I gave my son a turkey baster to continue the LEGO volcano eruptions. You can deliver the vinegar directly onto the remaining baking soda this way. It makes a cool eruption that keeps on going!

It kept on going…..

And going! Check out those bubbles!

Bonus Experiments With Baking Soda And Vinegar

More Fun LEGO Building Challenges

Make sure to also check out our free printable LEGO building challenges! There are tons of cool themes and topics to choose from!

Printable Brick Building Pack

Don’t want to bother checking out every link 👆, grab the huge brick bundle instead. Make it easy on yourself.

Visit the SHOP for the huge LEGO and brick building pack! 

  • 10O+ Brick theme learning activities in an e-book guide using the bricks you have on hand! Activities include literacy, math, science, art, STEM, and more!
  • A complete year of Brick themed seasonal and holiday challenges and task cards
  • 100+ page of The Unofficial Guide to Learning with LEGO ebook and materials
  • Brick Building Early learning pack filled with letters, numbers, and shapes!


  1. Pingback: 25+ LEGO Building Ideas To Keep Everyone Busy - Belle-Ve Bricks Blog %
  2. We had the best time this morning building the volcano and then making the chemical reaction. Very satisfying to attempt a cone formation of legos and to intentionally leave gaps- a little more thinking and time involved- that was my favorite part! My 3.5yo of course loved playing with the overflowing foam. Thanks for your content. I’m a newsletter subscriber since your earlier slime days. I love seeing your evolution and comforted by your emails reaching out to help parents during the covid19 quarantine. ❤️

  3. That made my day Emma! I am so happy it was a great experience for both of you. Who doesn’t love a LEGO volcano!

  4. We made a Lego volcano today and was such a hit !!
    Thank you so much for detailed steps
    Made for a perfect t afternoon of fun

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