The majority of the islands in the area are part of a coral atoll. Coral atolls begin as coral reefs that grow on the slopes of a central volcano. When the volcano sinks back down into the sea, the coral continues to grow, keeping the reef at or above water level. One exception is Pohnpei in the Federated States of Micronesia, which still has the central volcano and coral reefs around it.
The ?majority of the islands in the area are part of a coral atoll. Coral atolls begin as coral reefs that grow on the slopes of a central volcano. When the volcano sinks back down into the sea, the coral continues to grow, keeping the reef at or ,above water level. One exception. is Pohnpei in the Federated States of Micronesia, which still has the central volcano and coral reefs around it.