'Volcano in the lab' is a very popular activity with everyone. Using wax, sand and cold water, it models very successfully a volcanic plumbing system with the lava spreading out over the surface of the Earth at the top. In this model it is possible to see through the Earth's crust.
The wax can be re-used lots of times so it's a useful resource that you can keep ready.
This is one of many innovative ideas, all free to download from our website.