a group of small coral islands in the shape of a ring that encloses a lagoon
An atoll is formed first as a reef that fringes a volcanic island. As the island sinks (after the volcanic activity has ceased and the crust has cooled, becoming denser), the reef continues to build upward, eventually ending up as a ring-shaped structure.
the oppsite of atoll is planet
bikini atoll
Allot and atoll.
Atoll is a noun.
A lagoon boundary is an atoll.
A atoll
Let's not strand ourselves on this atoll.
Ailinglaplap Atoll's population is 1,959.
Aur Atoll's population is 438.
The population of Ujelang Atoll is 0.