atoll formation

An atoll forms when a volcanic island gradually erodes and sinks over millions of years. Coral reefs develop around the island’s perimeter, building upward as the island subsides. As the island disappears beneath the sea, the coral reef remains, creating a ring-shaped lagoon with a coral rim. This process involves volcanic activity raising the island, coral growth covering its edges, and erosion gradually lowering the land. The result is a low, circular coral reef structure that houses diverse marine life, typical of atolls.