The basic coral reef classification scheme described above was first proposed by Charles Darwin, and is still widely used today.
Darwin spent most of his coral reef explorations in the Indo-Pacific region, and viewed the three types of coral reefs he described as simply different stages in the geological ‘evolution” of Pacific oceanic islands.
Darwin theorized that fringing reefs began to grow near the shorelines of new islands as ecological conditions became ideal for hard coral growth.
Then, as the island began to gradually subside into the sea, the coral was able to keep pace in terms of growth and remained in place at the sea surface, but farther from shore; it was now a barrier reef.
Eventually, the island disappeared below the sea surface, leaving only the ring of coral encircling the central lagoon; an atoll had formed (see right).
Darwin’s general “reef evolution” theory was finally verified for Indo-Pacific reefs in the early 1950s after analyses of the results of deep core drilling at Bikini and Eniwetok Atolls.
However, it has also now become apparent that each of the three major types of coral reefs (described above) is often also formed by quite different geomorphic processes as well. The atoll-like Bahama Banks are a prime example of such alternate forms of reef development.