Updated by: Arabinda Naik
Submerged Volcanic Craters: The theory postulates that atolls are formed within the submerged craters of extinct volcanoes. These craters, once active volcanic calderas, have subsided below the ocean surface, providing a circular structure for coral reef growth.
Coral Reef Growth: Coral polyps colonize the submerged crater walls and the crater floor, gradually building up a coral reef within the crater. The reef grows upwards, keeping pace with rising sea levels during interglacial periods.
Atoll Formation: As the coral reef continues to grow, it eventually reaches the surface of the water, forming a ring-shaped structure around the central crater. The central lagoon of the atoll is formed by the crater itself, which remains submerged.
Role of Volcanic Fissures: Volcanic fissures, cracks in the lava rock, provide access for seawater into the crater, allowing coral polyps to establish themselves and initiate reef growth.