Atoll Atoll An atoll (, , , , or ), sometimes called a coral atoll, is a ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. The coral of the atoll often sits atop the rim of an extinct seamount or volcano which has eroded or subsided partially beneath the water. The lagoon forms over the volcanic crater or caldera while the higher rim remains above water(s) or at shallow depths that permit the coral to grow and form the reefs. For the atoll to persist,
Northern Thiladhunmathi Atoll Northern Thiladhunmathi Atoll Haa Alif Atoll - officially referred as Thiladhunmathi Uthuruburi (Northern Thiladhunmathi Atoll) is the northernmost administrative division of the Maldives. As the administrative division known as Haa Alif it includes Ihavandhippolhu, the northernmost natural atoll of the Maldive archipelago, as well as a section of the larger Thiladhunmathi or Tiladummati Atoll. Thiladhunmathi was divided into its northern and southern divisions on May 21, 1958. The north division was integrated with Ihavandhippolhu forming administratively a new atoll called Haa Alif atoll or Thiladhumathi North. In total Haa Alif atoll contains 42 islands, 14 of which are inhabited.At present