When was the first theory of coral reef formation proposed?

During the voyage of the Beagle and afterward, Charles Darwin studied coral reefs and proposed an influential theory in 1842. He argued that atolls formed as volcanic islands slowly sank while corals kept building upward near the surface. This idea helped explain the ring-shaped reefs seen in the Pacific and Indian Oceans. Darwin’s coral reef theory was an important contribution to marine geology and island science.