The so called ring of fire refers to a ring of volcanic activity that forms the boundaries of the Pacific Ocean, where it abuts the different continents. The origin of the ring is simply explained in the theory of plate tectonics. Magma (molten rock) will be generated in places where the pacific plate dives BENEATH the adjoining plate, a process called subduction. This molten rock then rises vertically to produce a large stratovolcano at the earth surface. Mt Fuji in Japan is a good example. if you Google the words subduction, Mount Fuji and plate tectonics, you can learn a great deal more about the ring of fire, plate tectonics, and subduction zone magmatism.