The baking soda volcano has been a classic in the Tony house for decades. Basically you mix baking soda and white vinegar then watch things erupt.
The main component of vinegar is acetic acid CH3COOH. Baking soda is NaHC03. When you mix them you get:
CH3C00H + NaHC03 => (CH3C00-)(Na+) + H20 + C02
That C02 being released is the cause of the fizzing. The food coloring is just a nice touch to give things the color of lava.
Here is my nephew Dr. T explaining things.