A reef that was once a large fringing reef that sinks an island is called what?

• A. Barrier reef
• B. Fringing reef
• C. Atoll
• D. Reef crest

Answer: (A)

Coral reef development follows a progression tied to land subsidence relative to sea level. A fringing reef forms directly along a coastline around an island. If the island begins to subside, the reef can keep growing upward and outward, creating a broader area of water between the reef and the shore. This configuration is called a barrier reef, which lies parallel to the coast with a lagoon tucked between reef and land. If subsidence continues until the island disappearing beneath the waves, the barrier reef may enclose a central lagoon and become an atoll. The term reef crest refers to the top edge of a reef, not a distinct stage formed by subsidence. So, in this scenario, the reef described is a barrier reef.