Why are the Society Islands surrounded by barrier reefs?

The Society Islands are surrounded by barrier reefs due to the geological development of their volcanic structures. According to the theory established by Charles Darwin, these reefs began as fringing reefs around volcanic islands. As the volcanic land subsided, the reefs grew upward and outward, creating a lagoon between the reef and the island.1

In the context of the Society Islands, which are primarily protrusions of submarine ridges, these volcanic cones have become highly eroded over time. The barrier reefs serve to protect these islands from the force of the sea, often encircling them completely. This process is a classic example of mid-ocean coral reef development, where the ocean floor subsides, allowing the coral to maintain its growth at the surface. While some islands in the region remain high volcanic peaks, others have subsided further, illustrating the various stages of this geological progression.21