The Maldives consists of 20 natural atolls, along with a few islands and isolated reefs stretching from 7 degrees 10 minutes north to 0 degrees 45 minutes south. The largest of these atolls is Boduthiladhunmathi, while the atoll containing the most islands is Huvadhu.
Some atolls are in the form of a number of islands, and others in the form of isolated reefs, which could be classified as smaller atoll formations. All land above the surface in the Maldives is of coralline origin. The atolls of the Maldives form a quite regular chain and, especially in the northern and central atolls, an arrayed structure is apparent. There are broad and deep channels between some atolls.H.C.P. Bell, The Maldive Islands, An account of the physical features, History, Inhabitants, Productions and Trade. Colombo The origin of the word "atoll" itself is in the language of the Maldives. "Atoll" (from ) is now used in many languages worldwide.
The atolls of the Maldives are and were very dangerous for navigators due to their complexity. In 1834–1836, British captain Robert Moresby undertook the cartography of the Maldives, drawing the first accurate maritime charts of the atolls.
These Admiralty charts were printed as three separate large maps by the Hydrographic Service of the Royal Navy. Moresby's charts were also favoured by Maldivian pilots navigating through the treacherous waters of the atolls until the 1990s.
Natural Atolls There are 27 Natural Atolls: Ihavandhippolhu, consider as part of Northern Thiladhunmathi Atoll Thiladhunmathi Uthuruburi / Northern Thiladhunmathi Atoll / Boduthiladhunmathi Uthuruburi / Haa Alif Thiladhunmathi Dhekunuburi / Southern Thiladhunmathi Atoll / Boduthiladhunmathi Dhekunuburi / Haa Dhaalu Makunudhoo, consider as part of Southern Thiladhunmathi Atoll Miladhunmadulu Uthuruburi / Northern Miladhunmadulu Atoll / Shaviyani Miladhunmadulu Dhekunuburi / Southern Miladhunmadulu Atoll / Noonu Maalhosmadulu Uthuruburi / Northern Maalhosmadulu Atoll / Raa Maalhosmadulu Dhekunuburi / Southern Maalhosmadulu Atoll / Baa Goifulhafehendhu Atoll / Goidhoo Atoll, consider as part of Baa Atoll Faadhippolhu Atoll / Lhaviyani Gaafaru Atoll (Gahaafaru Atoll), consider as part of North Malé Atoll North Malé Atoll / Kaafu Uthuruburi South Malé Atoll / Kaafu Dhekunuburi Ari Atholhu Uthuruburi / Northern Ari Atoll / Alif Alif Thoddoo Atoll, consider as part of Northern Ari Atoll Rasdhoo Atoll, consider as part of Northern Ari Atoll Ari Atholhu Dhekunuburi / Southern Ari Atoll / Alif Dhaal Felidhu Atholhu / Vaavu Mulaku Atholhu / Meemu Nilandhe Atholhu Uthuruburi / Northern Nilandhe Atoll / Faafu Nilandhe Atholhu Dhekunuburi / Southern Nilandhe Atoll / Dhaalu Kolhumadulu Atoll / Thaa Haddhunmathi Atoll / Laamu Huvadhu Atholhu Uthuruburi / Northern Huvadhu Atoll / Gaafu Alif Huvadhu Atholhu Dhekunuburi / Southern Huvadhu Atoll / Gaafu Dhaalu Fuvahmulah / Gnaviyani Addu Atoll / Seenu
There are 4 other minor atolls: Etthingili Alifushi Atoll - near Raa Atoll (Northern Maalhosmadulu Atoll) Fasdhuthere Atoll - between Raa Atoll (Northern Maalhosmadulu Atoll) and Baa Atoll (Southern Maalhosmadulu Atoll) Vattaru Atoll - located near Felidhu Atoll (Vaavu Atoll). Consider as part of Felidhu Atoll (Vaavu Atoll) Medhuthila Atoll - located between Haddhunmathi Atoll and Huvadhu Atoll
Administrative Atolls There are 21 Administrative Atolls (17 Atoll Councils and 4 Cities): Thiladhunmathi Uthuruburi / Northern Thiladhunmathi Atoll / Haa Alif , HQ: Didhdhoo Kulhudhuffushi City / Thiladhunmathi Dhekunuburi / Southern Thiladhunmathi Atoll / Haa Dhaalu [city] , HQ: Kulhudhuffushi Miladhunmadulu Uthuruburi / Northern Miladhunmadulu Atoll / Shaviyani , HQ: Funadhoo Miladhunmadulu Dhekunuburi / Southern Miladhunmadulu Atoll / Noonu , HQ: Manadhoo Maalhosmadulu Uthuruburi / Northern Maalhosmadulu Atoll / Raa , HQ: U'ngoofaaru Maalhosmadulu Dhekunuburi / Southern Maalhosmadulu Atoll / Baa / , HQ: Eydhafushi Faadhippolhu Atoll / Lhaviyani , HQ: Naifaru Kaafu / Malé Atholhu , HQ: Thulusdhoo Malé City [city] , HQ: Malé City Ari Atholhu Uthuruburi / Northern Ari Atoll / Alif Alif , HQ: Rasdhoo Ari Atholhu Dhekunuburi / Southern Ari Atoll / Alif Dhaal , HQ: Mahibadhoo Felidhu Atholhu / Vaavu , HQ: Felidhu Mulaku Atholhu / Meemu , HQ: Muli Nilandhe Atholhu Uthuruburi / Northern Nilandhe Atoll / Faafu , HQ: Nilandhoo Nilandhe Atholhu Dhekunuburi / Southern Nilandhe Atoll / Dhaalu , HQ: Kudahuvadhoo Kolhumadulu Atoll / Thaa , HQ: Veymandoo Haddhunmathi Atoll / Laamu , HQ: Fonadhoo Huvadhu Atholhu Uthuruburi / Northern Huvadhu Atoll / Gaafu Alif , HQ: Villingili Huvadhu Atholhu Dhekunuburi / Southern Huvadhu Atoll / Gaafu Dhaalu , HQ: Thinadhoo Fuvahmulah City / Gnaviyani [city] , HQ: Fuvahmulah City Addu City / Seenu [city] , HQ: Hithadhoo
Ihavandhippolhu Ihavandhippolhu Atoll is the northernmost atoll in the Maldives. It is a small natural atoll in length.
It has 25 islands lying all around the boundary reef. One long barrier reef forms the western side of the atoll. There are several coral patches in the lagoon and the general depth in the centre is 20 to 30 fathoms (35 to 55 m).
Ihavandhippolhu is bounded in the north by the broad channel known as Māmalē Kandu (or Maliku Kandu) which separates the islands of Maldives from those belonging to India.
Administratively, Ihavandhippolhu belongs to the North Thiladhunmathi (Haa Alifu) Atoll administrative division which also includes the northernmost portion of the Thiladhunmathi natural atoll.
Thiladhunmathi Boduthiladhunmathi Atoll is the largest of the Maldives atolls and the world's largest atoll (not taking into account the mostly submerged Great Chagos Bank and Saya de Malha Bank). It is very open, a typical atoll without a clearly delimited lagoon.
It is a huge atoll stretching SSW for and contains nearly forty islands generally of a fair size. Kelaa, a large island forms a prominent point in the NE of this atoll.
The western boundary has fewer islands but more isolated reefs or micro-atolls (called faru in Maldivian), with wide passages between them. The German explorer Hans Hass observed the formation of this phenomenon called "micro-atoll" by Porites corals in the Maldives. Its lagoon has few shoals but many large faru, often topped with islands. The average depth is from .
The Miladhunmadulu group is also naturally a part of Thiladhunmati Atoll, comprising the southern half of the atoll. The length of this part of the atoll is and it contains 101 islands.
The general depth of the centre of this part is and the bottom is sandy. Along its western edges there are not many islands but more detached reefs with shallow lagoons (called vilu in Maldivian) which seldom exceed in depth.
Administratively, Thiladhunmathi Atoll together with the Miladhunmadulu group are divided among four administrative divisions, namely North Thiladhunmathi (Haa Alifu) Atoll, South Thiladhunmathi (Haa Dhaalu) Atoll, North Miladhunmadulu (Shaviyani) Atoll and South Miladhunmadulu (Noonu) Atoll.
Maamakunudhoo Māmakunudhoo Atoll or Makunudhoo is the westernmost atoll in the Maldives. A large reef with lagoon, long with and average breadth of . It has only one inhabited island, Makunudhoo and three other islands (namely Innafushi, Fenboahuraa and Dhipparufushi) and it lies west of the NW part of the Miladhummadulhu group. It is said to have been unknown to non-Maldivians previous to the 1834–36 survey of the Maldives. According to the locals, many ships have been lost on its barren reefs with crew, cargo and all. These include the Persia Merchant (August, 1658), Hayston (July, 1891), George Reid (September, 1872) and many more. Owing to the violence of the surf and the perpendicular sides of the reef scarcely a vestige of the wreck remains after a few hours. The lagoon is quite deep but it is full of coral patches.
Etthingili Alifushi Atoll Etthingili Alifushi Atoll consists of two islands, Alifushi and Etthingili (also known as Kalhifushi), known as 'The Powell Islands' in the Admiralty Chart. The islands stand on a detached reef of their own with very deep waters (no sounding) between this reef and the northern end of the main Atoll. The length of this atoll is with a width of . Today, of the two islands, only Alifushi is inhabited.
Maalhosmadulu Uthuruburi
Maalhosmadulu Uthuruburi (Northern Maalhosmadulu Atoll) is in length from N to S, and across at its broadest part. Its western fringe is composed of a series of round or oval reefs (farus) irregularly placed (a feature peculiar to all the larger Northern Atolls). The centre is heavily dotted with coral patches (giri), some submerged and some awash. The concentration of giri is especially dense towards its SW quarter, close to Kandholhudhoo Island (where there is the place most crowded with small reefs and shoals in the whole Maldives), but its narrower northern end is quite clear of reefs. The general depths of the lagoon are from 23 to 27 fathoms (42 to 49 m).
Fasdhooethere (Fasdhoothere) Fasdhootherey Atoll is sandwiched between two atolls, the northern part of South Maalhosmadulu forms a clearly delimited, roughly triangular, natural atoll without a distinctive name ( means 'between five islands'). It is in length from east to west. It has 11 islands with the only inhabited island being Kudarikilu Island on its SE corner just opposite Landaa Giraavaru Island of Southern Maalhosmadulhu Atoll. Its lagoon becomes narrower towards the west and its average depth is . It is separated from North Maalhosmadulhu by a deep channel (known as Moresby Channel in the Admiralty Chart and Hani Kandu locally) and from the southern part of Southern Maalhosmadulhu Atoll by the narrow Geydhoshu Kandu (also known as ) running from east to west.
Maalhosmadulu Dhekunuburi Maalhosmadulu Dhekunuburi (Southern Maalhosmadulu Atoll) has many large farus on its western side. Its maximum length is . The inner lagoons (vilu) present an idyllic view. The depth of their waters is not more than a few meters, with perhaps a few coral heads awash. Its eastern fringe is a succession of separate, quite regular, oval reefs with some islands. The interior of the lagoon has also large faru towards its southern half. The average depth is from 24 to 27 fathoms (44 to 49 m).
Goidhu Atoll Goidhu Atoll or Goifulhafehendhu Atoll is separated from South Maalhosmadulhu by a channel. This atoll is oval in shape and small, its greatest length being . It is composed of 7 islands, 3 of which are inhabited. The inner lagoon has a depth of 17 to 20 fathoms (31 to 37 m); it has a sandy bottom mixed with mud and clay. Unlike the lagoons of most small atolls of the Maldives, this lagoon is free from coral heads in its centre.
Faadhippolhu Faadhippolhu Atoll (better known as Lhaviyani Atoll) is a smaller atoll with a well-defined barrier reef to the east, on which the NE monsoon (iruvai) breaks with violence. Its western side has farus and reef patches. There are about 52 islands, of which only 5 are inhabited. The lagoon is fairly open and its general depths are from 25 to 30 fathoms (about 50 m). Its bottom is sandy and there are a number of coral patches and sunken reefs dotting it, except for the south-eastern side.
Kaashidhu Atoll Kaashidhu Atoll, lies towards the eastern end of the channel to which it gives its name . This atoll had two islands namely Kaashidhoo and Kaashidhoo Huraa from which only Kaashidhoo exists today. Kaashidhoo is surrounded by deep waters and there is generally heavy surf all around. The Atoll has an oval-shaped lagoon (vilu) with a narrow fringing reef on its NW side.
Gahaafaru (Gaafaru) Atoll