For the manufacture of the volcanoand take the clay (or the clay or dough), glass jar, pre-buried in the sand. Now put a jar on a stand and shape it around your volcano with a crater (they will be the bottom of the jar).
Now take a tablespoon of baking soda, a tablespoon of dishwashing detergent, 2-3 drops red food coloring (you can use beet juice).
Then pour into the imaginary mouth of the volcanoand about 50 ml of vinegar. You will observe the eruption from vents will be cut seething foam.
It turns out that thanks to a chemical reaction in which carbon dioxide, it bubbles, the mass is beyond the edge of the crater. By the way, liquid for washing dishes makes the imaginary lava to boil as much. The process is completely safe and is not harmful. Don't worry, the child in any case will not suffer from burns, poisoning and other troubles.
Please note that the experience is better to put in a room with good ventilation because of the not very pleasant smell of vinegar. Also be sure to tell your kid that these experiments are made only with adults.