For atolls, it begins in fire spewing from the ocean floor and building a submarine volcano and then an island. Coral arrives on sea currents carrying its larvae, eggs, and sperm. Because of the Intertropical Convergence Zone, Palmyra has a rich diversity of coral, arriving from both the east and west.
Coral clings to the volcanic island, forming a fringing reef. Over millions of years the land sinks and shrinks, and a lagoon forms, separating the reef from the shore. Finally, the volcano submerges, leaving, at Palmyra, 15,000 acres of coral reef, circling a lagoon where once an volcano stood.