How did underwater volcanoes form many of the Society Islands?

Most of the Society Islands in French Polynesia were formed by the emergence of underwater volcanoes. These islands are essentially protrusions of submarine ridges, where volcanic activity built up cones from the seafloor.1

While many volcanoes globally are associated with plate boundaries, the Society Islands are part of a broader pattern of oceanic island formation often linked to hotspots—regions where magma from the mantle penetrates the crust. As a tectonic plate moves over such a stationary heat source, a chain of volcanoes is created. Over time, these volcanic structures become extinct as they move away from the magma source, subsequently cooling, subsiding, and eroding. This process often leads to the development of fringing reefs and atolls around the volcanic remnants. Today, the Society Islands are characterized by these highly eroded volcanic cones, which are often protected by encircling barrier reefs.23451