In The Voyage of
the Beagle, Charles Darwin explained his theory of how coral atolls are
created. His theory is essentially the currently accepted idea. Return to my Biology pages
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© Copyright 1999, Jim Loy
In The Voyage of
the Beagle, Charles Darwin explained his theory of how coral atolls are
created. His theory is essentially the currently accepted idea.
In the ocean, a volcano emerges up out of the sea. It builds up by depositing lava on top of lava. Soon, living organisms (including coral) begin living around the shores of the new island. The volcano becomes dormant, and begins to slowly sink (higher land tends to sink).
As the island sinks, old coral dies. Some of it dies because it is now in water that is too deep. But, new coral grows on top of the old, dead coral. The island now has a ring of coral around it. A lagoon separates the island from its ring of coral. Less robust species of coral live in the lagoon, sheltered by the hardier coral at the edge.
Eventually, the island sinks under the sea. And all that is left is the ring of coral, with a shallow lagoon in the middle. The island has become a coral atoll.