The Pacific Ocean is ringed by more than 450 active and dormant volcanoes, a chain stretching from the Aleutian Islands down through Japan and Southeast Asia to the Andes. This film traces that chain and explains why it exists: dense oceanic plates sliding beneath lighter continental plates in a process called subduction, generating enough heat and pressure to build volcanic peaks over millions of years. Mount St. Helens and Mount Fuji serve as the film's two central examples, one an eruption still within living memory, the other a near-symmetrical cone that has shaped Japanese culture for centuries. The film links this same subduction activity to the earthquakes that regularly strike the Pacific coastlines, treating volcanism and seismicity as two symptoms of the same underlying mechanism. It also touches on the millions of people who live within reach of these volcanoes, farming the fertile soil their eruptions have created while accepting the risk that comes with it.