Atoll development
![A series of 4 cartoon to illustrate how we go from an active volcanic island, to fringing and barrier reef, to atoll.](https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/styles/full_width/public/thumbnails/image/Atoll-USGS-FS25-02.jpg?itok=wbe8Ay9l)
Detailed Description
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 steep-walled 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. Graphic Design By Susan Mayfield and Sara Boore, USGS Fact Sheet 025-02