Atoll
Lagoon
Explanation:
Coral reefs that surrounds an island are called atoll and the restricted waters behind the barrier forms the marine environment of a lagoon. Coral reefs are fascinating and beautiful geological features created by geology and activities of corals. 
- In a marine environment, serious of underwater volcanoes can build to reach the surface of water. 
- In this case, they for island arcs. Corals can build up on these arcs the forms to form a coral reef. 
- The backwater cutoff from the main water body is a lagoon. 
- The Island capped by the corals eventually subsides and leaves the corals above the surface of the water. 
- This is a typical way in which coral reefs form. 
Learn more: 
Tectonics https://brainly.com/question/9582362
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