Areef that surrounds a volcanic island is a(n): atoll guyot graded bed turbidity current

A reef than surrounds a volcanic island is an : Atoll

Atoll usually takes shapes in a form of ring that surround the areas of volcanic island that consist of corals. It usually only exist in warm waters, so volcanic islands will provide perfect environment for the corals

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The answer is c) people evacuated but almost all returned

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