The answer is its' tectonic forces that affect the earth's surface. In fact, it is called the ring of fire mainly because the subduction of the oceanic crust below the continental crust gives rise to the creation of magma which either forms slowly cooled igneous rock or volcanic activity and the western edge of North, Central and South America has numerous volcanoes such as Popacapetl in Mexico, Fuego in Guatemala and Chimborazo in Ecuador.
