Question: How does a volcano form ?

Volcanoes form when magma from inside the Earth erupts out onto the surface. Particularly, magma is quite lazy and it will find the easiest route to get from inside the Earth to outside of the Earth. As the best route is found, more and more magma will erupt onto the surface from the same place and it will slowly build up the mountain of a volcano. Sometimes if magma decides to switch the route it takes to the surface it can produce a line of volcanoes a bit like what you see in Hawaii!