Situated on the Cagayan Ridge, a string of extinct underwater volcanoes, Tubbataha is the Philippines' only true atoll structure. According the theory by Charles Darwin, atoll formation begins when a volcanic eruption gives birth to an island. So, it is believed that the atolls of Tubbataha began to form thousands of years ago as fringing reefs around volcanic islands.
Over millennia – as the volcanoes became extinct and the islands subsided – only the corals remained as they continued to grow upwards, towards the sunlight. The original fringing reefs eventually turned into the giant rings of corals that we see today encircling shallow lagoons.