This animation shows the three-dimensional structure of a "mid-ocean ridge", where two of the Earth's tectonic plates are spreading apart. The Earth's mantle wells up between the separating plates and melts, which feeds magma to active volcanoes along the spreading ridge. This ridge is adjacent to a "subduction zone", which is another setting where active volcanoes form, but due to plates converging instead of spreading apart. Both spreading ridges (like Explorer Ridge) and subduction zones (like the Marianas Arc) make up parts of the Submarine Ring of Fire. Animation by Clay Hamilton and Bill Chadwick.