How Did Charles Darwin Explain the Origin of Fringing Reefs?

💡 The Answer

• Darwin’s subsidence theory proposed that fringing reefs form first on volcanic islands, then transform into barrier reefs and atolls as the island slowly sinks.
• He observed that fringing reefs grow upward to stay in sunlit water as the underlying land subsides, creating a lagoon.
• The theory was later confirmed by deep drilling on Pacific atolls, which found volcanic rock beneath thick coral layers.
• This evolutionary sequence explains why fringing reefs are typically younger and found around younger volcanic islands.