Why do hotspot islands form chains?
Hotspot island chains form as a moving plate passes over a relatively persistent magma source and creates volcanoes in sequence.
Formation process and geographic mechanism
Magma builds a submarine volcano while the plate overlies the hotspot, and continued growth may create an island. As the plate moves, the old volcano leaves the source, activity wanes and a new volcano forms elsewhere. Island and seamount ages generally increase away from the active end. Bends in the chain can record changes in past plate motion.
Spatial outcomes, measurement and management
Treating a hotspot as perfectly fixed is a simplification; mantle sources can move slowly and volcanism may be broad. Dating, rock chemistry, seafloor mapping and GPS are combined. Volcanic islands erode and subside with cooling oceanic crust, while coral growth can create reef and atoll stages in suitable regions.