How do atolls form?
A) A fringing reef around a volcanic island grows upward as the island sinks.
B) A caldera on a volcanic island fills with water.
C) The central portion of a reef sinks below sea level, leaving a ring around the outer edge.
D) Organisms on the outer edge of a reef grow more quickly than organisms in the center.

Question

Quizplus · Accepted Answer

Atolls form when a fringing reef around a volcanic island grows vertically while the island gradually sinks beneath the ocean surface. This process continues until the island disappears below the surface, leaving a circular coral reef, or atoll, with a lagoon in the center.

How Do Atolls Form