Atoll

ocean · coral · tropical · geography

Ring of coral. An atoll is shaped like a giant donut made of coral, with a shallow lagoon in the middle instead of a hole. The coral rim grows up from the deep ocean floor to create this special shape.

Warm water homes. Atolls only form in warm tropical and subtropical oceans where coral can grow healthy and strong. Most of the world's approximately 440 atolls are found in the Pacific Ocean.

Islands on the rim. The coral ring of an atoll isn't always solid, it often has small coral islands or cays dotted around it. These tiny islands give sailors and animals places to land and rest.

Lagoon inside. The water inside the lagoon is usually calm and shallow, creating a peaceful home for fish, turtles, and other ocean creatures. It's like nature's own perfect swimming pool surrounded by protective coral.