The Atlantic has a stunning gallery of the year 2012 in volcanic activity that you really want to check out.
Ever since our planet formed from a cloud of condensed stellar dust, the dense heat of our interior has created a molten core surrounded by a thin candy shell of solid rock. That shell continues to evolve, leaking magma via cracks in its moving surface, via events both quiet and violent.
Such is the continual evolution of our planet. It’s a beautiful process, assuming you’re looking at it in a photograph, rather than while running in fear from the bottom of the mountain where it’s occurring.