<p>Internationalization of the diagram:Atoll forming.<br><b>1</b>=Volcanic Island<br><b>2</b>=Fringing reef<br><b>3</b>=Barrier reeef<br></p>
Caption: Coral atolls develop from reefs fringing volcanic islands. As first hypothesized by Charles Darwin, and confirmed by ocean drilling done by British scientists a century ago, reefs fringing volcanic islands build vertically to sea level, forming steepwalled barrier reefs. As a volcanic island subsides, or sinks, with time, the growing reef keeps pace with the rising water level. When the island eventually submerges, the ring-shaped reef forms an atoll with a central lagoon.
Susan Mayfield and Sara Boore, modified by Eurico Zimbres
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