Why do volcanoes form in chains?

Volcanoes often form in chains due to tectonic activity at plate boundaries or hotspots. At convergent boundaries, like subduction zones, magma rises as one plate sinks beneath another, creating a chain of volcanoes along the boundary. Hotspots, such as the one beneath Hawaii, occur when magma from deep within the mantle rises to the surface through a stationary plume. As tectonic plates move over the hotspot, a series of volcanoes forms, creating island chains.