Tuvalu Tuvalu ( or ; formerly known as the Ellice Islands) is an island country and microstate in the Polynesian subregion of Oceania in the Pacific Ocean. Its islands are situated about midway between Hawaii and Australia. They lie east-nor ...

consists of nine separate islands: six

atoll An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical oceans and seas where corals can gr ...

s and three

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...

islands. An atoll typically consists of several

islet An islet is a very small, often unnamed island. Most definitions are not precise, but some suggest that an islet has little or no vegetation and cannot support human habitation. It may be made of rock, sand and/or hard coral; may be permanen ...

s: Tuvalu has a total of 124 islands and islets. Each island is surrounded by a

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. C ...

. Tuvalu's small, widely scattered atolls have poor soil and a total land area of only about making Tuvalu the fourth-smallest country in the world. The sea level at the Funafuti tide gauge has been rising at a rate of 3.9 mm per year, and it has been determined that

rising sea levels Rising may refer to: * Rising, a stage in baking - see Proofing (baking technique) *Elevation * Short for Uprising, a rebellion Film and TV * "Rising" (''Stargate Atlantis''), the series premiere of the science fiction television program ''Starga ...

are causing more wave energy to be transferred across reef surfaces, which has tended to push more sand onto island shorelines, increasing islands’ land area. Over a recent four-decade period, there was a net increase in the land area of the islets of 2.9% (73.5 ha), although the changes were not uniform: About 74% of them increased in size and about 27% decreased in size.

Islands of Tuvalu

The islands of Tuvalu are spread out between the

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

of 5° to 10° south and

longitude Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lette ...

of 176° to 180°, west of the International Date Line. The name, Tuvalu, means "eight standing together" in Tuvaluan. The Coral reefs of Tuvalu consists of three

islands and six atolls, containing approximately of reef platforms. The reef islands have a different structure to the atolls, and are perhaps better described as “reef platforms,” as they are small, tabular platforms that lack the salt-water

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') ...

typically found on reef islands. The reef platforms do have a completely enclosed rim of dry land, and the rim surrounds the remnants of a lagoon, but these lagoon remnants have no connection to the open sea, and tend to dry up as coral debris accumulates in them over time. For example,

Niutao Niutao is a reef island in the northern part of Tuvalu. It is one of the nine districts (islands) of Tuvalu. It is also one of the three districts that consist of only one island - not counting the three islets inside the closed lagoon. Niutao has ...

has two brackish, saline lakes which are the degraded remnants of an ancient lagoon. The smallest island, Niulakita, which is the ninth island in the Tuvaluan archipelago, has not been continuously inhabited. It has been privately owned since 1944, when the Gilbert and Ellice Islands Colony administration purchased the island and granted people from

Vaitupu Vaitupu is the largest atoll of the nation of Tuvalu. It is located at 7.48 degrees south and 178.83 degrees east. There are 1,061 people (2017 Census) living on with the main village being Asau. Geography The island, which covers approxima ...

permission to settle there. However, in 1949, a successor administration made the controversial decision to expel the Vaitupuans from Niulakita, and arrange for residents of

to settle there instead, because Niutao was felt to be overpopulated. Niulakita is a separate local government district, but it is administered as part of Niutao, and is represented in the Parliament of Tuvalu by members of the constituency of Niutao. At least 11 islands are inhabited, expanded over the biggest isles of the nine atolls, plus two islands in

Funafuti Funafuti is the capital of the island nation of Tuvalu. It has a population of 6,320 people (2017 census), and so it has more people than the rest of Tuvalu combined, with approximately 60% of the population. It consists of a narrow sweep of lan ...

. Tuvalu has ISO 3166-2 codes defined for 1 town council (Funafuti) and 7 island councils. Niulakita, which now has its own island council, is not listed as it is administered as part of Niutao.

Royal Society of London investigation of the formation of coral reefs at Funafuti

An expedition (''Funafuti Coral Reef Boring Expedition of the Royal Society'') under Professor William Sollas of

Oxford University Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to th ...

, conducted by the

Royal Society of London The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

carried out drilling on the

in 1896, 1897 and 1898. HMS ''Penguin'', under the command of Captain Arthur Mostyn Field, delivered the 1896 expedition to

in the

Ellice Islands Tuvalu ( or ; formerly known as the Ellice Islands) is an island country and microstate in the Polynesian subregion of Oceania in the Pacific Ocean. Its islands are situated about midway between Hawaii and Australia. They lie east-nor ...

, arriving on 21 May 1896, and returned to Sydney on 22 August 1896. From 1896 to 1899 the ''Penguin'' was under the command of Captain Arthur Mostyn Field and her surveying work included further voyages to

atoll to deliver the expeditions of the Royal Society in 1897 and 1898. The surveys carried out by the ''Penguin'' resulted in the preparation of the Admiralty Nautical Chart 2983 for the islands. The Royal Society of London were investigating the formation of coral reefs and whether traces of shallow-water organisms could be found at depth in the

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and ...

of Pacific

s. Three expeditions used drilling equipment to take core samples of the coral reef. The boreholes on

Fongafale Fongafale (also spelled Fogale or Fagafale) is the largest of Funafuti's islets in Tuvalu. It is a long narrow sliver of land, 12 kilometres long and between 10 and 400 metres wide, with the South Pacific Ocean and reef on the east and the protec ...

islet are at the site now called ''Darwin's Drill'', A goal of the expeditions was to drill down to confirm that the coral material was located on a base of volcanic rock. This investigation followed the work on the structure and distribution of coral reefs conducted by

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...

in the Pacific. However, the geologic history of atolls is more complex than Darwin (1842) and Davis (1928) envisioned.

First expedition (1896)

The expedition was led by Professor

William Johnson Sollas Prof William Johnson Sollas PGS FRS FRSE LLD (30 May 1849 – 20 October 1936) was a British geologist and anthropologist. After studying at the City of London School, the Royal College of Chemistry and the Royal School of Mines he matriculat ...

of the

University of Oxford , mottoeng = The Lord is my light , established = , endowment = £6.1 billion (including colleges) (2019) , budget = £2.145 billion (2019–20) , chancellor ...

and included Professor

Edgeworth David Sir Tannatt William Edgeworth David (28 January 1858 – 28 August 1934) was a Welsh Australian geologist and Antarctic explorer. A household name in his lifetime, David's most significant achievements were discovering the major Hunter ...

and Walter George Woolnough of the

University of Sydney The University of Sydney (USYD), also known as Sydney University, or informally Sydney Uni, is a public research university located in Sydney, Australia. Founded in 1850, it is the oldest university in Australia and is one of the country's ...

Second expedition (1897)

The expedition was led by Professor

of the

(that included George Sweet as second-in-command, and Walter George Woolnough).

Third expedition (1898)

The expedition was led by Alfred Edmund Finckh of the University of Sydney.

Results of the Royal Society expeditions

The purpose of the expedition was to attempt to settle the question as to the formation of coral atolls. The first expedition experienced defects in the boring machinery and the bore penetrated only slightly more than 100 feet (approx. 31 m). The second expedition reached a depth of 557 feet (170 m). The third expedition was successful in carrying the bore to 1,114 feet (340 m). The results provided support for

's theory of subsidence; in which there are four stages in development of coral reefs: a

volcanic island Geologically, a high island or volcanic island is an island of volcanic origin. The term can be used to distinguish such islands from low islands, which are formed from sedimentation or the uplifting of coral reefs (which have often formed ...

forms, is surrounded by a fringing

, as it subsides slowly a wide barrier reef forms, then after it has sunk below sea level the coral continues to grow forming a circular

. However, the geologic history of atolls is more complex than Darwin (1842) and Davis (1920 & 1928) envisioned.

Structure of Funafuti atoll

The average depth in the Funafuti lagoon (''Te Namo'') is about 20 fathoms (36.5 metres or 120 feet).

References

{{DEFAULTSORT:Islands Of Tuvalu Subdivisions of Tuvalu Tuvalu, Islands Tuvalu 1

Tuvalu-related lists