বিবরণBritannica Coral-reefs Atoll Formation.png	English: A diagram showing Charles Darwin's theory of atoll formation via coral formation on subsiding rocks.
তারিখ	১৯১১
উৎস	Encyclopaedia Britannica (11th ed.), v. 7, p. 133
লেখক	অজানাUnknown author
অনুমতি (এ ফাইলের পুনঃব্যবহার)	Public domainPublic domainfalsefalse This image comes from the 13th edition of the Encyclopædia Britannica or earlier. The copyrights for that book have expired in the United States because the book was first published in the US with the publication occurring before January 1, 1929. As such, this image is in the public domain in the United States.

Legend:

Diagram showing the formation of an atoll during subsidence. (After C. Darwin.) The lower part of the figure represents a barrier reef surrcunding a central peak.

A,A, outer edges of the barrier reef at the sea-level; the coconut trees indicate dry land formed on the edges of the reef.

L L, lagoon channel.

A',A', outer edges of the atoll formed by upgrowth of the coral during the subsidence of the peak.

L', lagoon of the atoll.

The vertical scale is considerably exaggerated as compared with the horizontal scale.