When continental crust collides with continental crust , however, something different happens. Because of their equal densities they simply smash into each other, bunching up. When continents collide with continents, impressive mountain ranges usually result, although this type is rarely associated with volcanoes. Follow the link to see this in action. Subduction and the forces associated with it can create spectacular mountain ranges.
Volcanoes can also form by other mechanisms besides subduction.
There are spots on earth where stationary magma plumes burn like a welder's torch at plates moving over them, creating a string of volcanoes lined up in the direction of plate motion. The Hawaiian Islands were created this way.