Anomalous arc volcanoes tend to exist where a linear topographic feature (fracture zone, line of seamounts, or ridge) on the oceanic plate is subducting. “Dots-and-lines tectonics” are proposed for clarifying this tendency and understanding the mechanisms that generate it. State-of-the-art studies on along-arc variations of volcanism around the Pacific ring of fire and possible effects of inhomogeneities on the subducting oceanic plate are reviewed. Mechanisms generating the clustered distribution of active volcanoes in North-eastern Japan and the extraordinary volcanism at Mount Fuji are reconsidered from a “dots-and-lines” tectonics point of view. Although there still remain many unsolved problems, “dots-and-lines” tectonics could offer a unified explanation of along-arc variations in volcanism, combining processes in mid-ocean ridges, hot spots, and subduction zones.