Why do hotspots create chains of volcanoes?

Hotspot volcanism is usually explained by a mantle plume, a rising column of unusually hot mantle material. The plume can melt rock and feed a volcano through a crack in the overlying plate. As the plate drifts, the volcano is carried away from the heat source and eventually shuts down, while a new volcano forms over the hotspot. The Hawaiian Islands are the best-known example, with the Big Island currently active and older islands stretching northwest across the Pacific. This pattern records both plate motion and long-term mantle activity.