Fringe Reefs

Fringe reefs are reefs located a little ways off of the coast. A small lagoon is formed in between the reef and the coast. Fringe reefs are the most common reefs.

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Barrier Reefs

Barrier reefs are located farther from the coast, forming a large lagoon. Probably the most famous reef, the Great Barrier Reef, is about 100 km off of the coast of Australia.

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Atolls

Atolls are often formed as barrier reefs or fringe reefs but then, as the ocean rises, the island is submerged and the reef is a ring in the ocean. This creates a round lagoon.