The building of mountains comes from convergent boundaries, because when two plates ram into each other, it creates a mountain. It's like having 2 piles of sand. When you try and shove them together, they end up forming a hill instead of making a neat surface. Volcanoes often occur at subduction zones (look up the ring of fire (not the song ;) ) because when the plate from the ocean sinks into the mantle, the water it absorbed lowers the melting point of the rock. This makes the rock turn into magma which rises to the surface and forms volcanoes.
