New research on the formation and evolution of coral atolls may disprove one of Charles Darwin's most controversial theories.
Darwin's 1842 theory said that coral atolls -- the ring-shaped reefs that surround tropical islands -- form as the coral formations cling to lava and debris from the island, growing upwards toward the sun while the sea surface sinks as the ocean crust cools and the weight of the island presses downward.
But a team of researchers from the Massachusetts Institute of Technology, using computer models to test Darwin's theory, found he underestimated the complexity and variety of atoll formations around the world.
Instead, the "see-sawing" rising and falling sea levels are at the heart of the distinct formations of the ringed reefs.
"Darwin actually got it mostly right, which is pretty amazing," Taylor Perron, a geologist at MIT and the study's co-author, told OurAmazingPlanet. But, Perron said, "he didn't know about these glacially induced sea-level cycles."
While most of his contemporaries thought atolls were only thin sheaths of coral, Darwin believed -- correctly, as it turned out -- they can grow to thousands of feet thick.
But Darwin's theory could not explain the wide variety of reef formations, which is where the new research comes in.
"You can explain a lot of the variety you see just by combining these various processes -- the sinking of islands, the growth of reefs, and the last few million years of sea level going up and down rather dramatically," Perron said.
Darwin did his research in the Society Islands in the South Pacific, where the sinking of islands and rising sea level create perfect atolls.
But in places like Hawaii, where the water is colder and the volcano forming the Big Island is sinking rapidly, the reefs that form when sea level is lower can't keep up when glacial melt causes sea levels to rise.
The MIT research was published in the May 9 Geology journal.