Atoll Atoll An atoll (, , , , or ), sometimes called a coral atoll, is a ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. The coral of the atoll often sits atop the rim of an extinct seamount or volcano which has eroded or subsided partially beneath the water. The lagoon forms over the volcanic crater or caldera while the higher rim remains above water(s) or at shallow depths that permit the coral to grow and form the reefs. For the atoll to persist,
Palmyra Atoll the north, followed by Kaula Island in the south. The northern arch of islets is formed by Strawn Island, Cooper Island (or Cooper-Meng Island since former Cooper and Meng Islands were joined in 1940), Aviation Island, Quail Island, Whippoorwill Island, followed in the east by Eastern Island, Papala Island and Pelican Island, and in the south by Bird Island, Holei Island, Engineer Island, Tanager Island, Marine Island, Kaula Island, Paradise Island, the Home Islets and Sand Island (clockwise). Palmyra Atoll is in the Samoa Time Zone (UTC−11:00), the same time zone as American Samoa, Midway Atoll, Kingman Reef and Jarvis