This "recipe" resulted in a very successful volcanic eruption in our sandbox today. Give it a try if you're in the mood for a backyard natural disaster.
Baking Soda Volcano
1. Find a cup or soda bottle for your crater (we buried ours in sand to look volcano-ish).
2. Fill your cup or bottle most of the way full with warm water. Add a bit of food color if desired.
3. Add 6 drops of detergent to the bottle contents. The detergent helps trap the bubbles produced by the reaction so you get better lava.
4. Add 2 tablespoons baking soda to the liquid.
5. Slowly pour vinegar into the bottle. Watch out - eruption time!