Our original plan was to make just one volcano. But, the girls were having a lot of fun and kept asking for more volcanoes. So, to avoid using up all of the vinegar we had, we switched to making "little volcanoes."

I highly recommend making small volcanoes - they had the same impact as the large ones and used a lot less vinegar.

The girls added in their own baking soda (first they made green and purple volcanoes):

Then the girls made red and blue volcanoes: