Coral reef A fringing reef forms around an extinct volcanic island as the island and ocean floor subsides. As the subsidence continues, the fringing reef becomes a barrier reef and ultimately an atoll reef. Darwin predicted that underneath each lagoon would be a bedrock base, the remains of the original volcano. Subsequent research supported this hypothesis. Darwin's theory followed from his understanding that coral polyps thrive in the tropics where the water is agitated, but can only live within a limited depth range, starting just below low tide. Where the level of the underlying earth allows, the corals grow around the coast
Coral Sea Islands areas for birds and turtles but contain negligible natural resources. They comprise less than of land. There is no port or harbour, only offshore anchorage. Most of the atolls fall into two groups, while Mellish Reef to the east, and Middleton Reef and Elizabeth Reef to the south are grouped separately: The atolls of the Northwestern Group, except Osprey Reef and Shark Reef in the north, and Marion Reef in the south, are located on the Coral Sea Plateau (Queensland Plateau), a contiguous area of depths less than 1000 m. The Nature Reserves were created to protect wildlife in the