Distribute a large paper plate and a small cup to each child. Instruct the children to place the cups in the center of the plate.
Pour a teaspoon of baking soda in each cup. (Older children can fill their own teaspoons and carefully pour the soda into their cups.)
Mix vinegar with a few drops of red food coloring, to simulate the gushing lava.
Explain that as soon as the vinegar meets the baking soda, they will form a gas and that this gas will react and bubble over.
Pour vinegar into the first cup. The mixture will immediately bubble up and fizz over the cup, into the plate. Repeat with all the remaining cups of baking soda. Enjoy!