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Ireland (left) and Great Britain (right), are large islands of north-west Europe MODIS - Great Britain and Ireland - 2012-06-04 during heat wave.jpg
Ireland (left) and Great Britain (right), are large islands of north-west Europe
Cyprus island the third largest in the Mediterranean as viewed from space. CyprusFromTheISS.jpg
Cyprus island the third largest in the Mediterranean as viewed from space.
A small island in Lower Saranac Lake in the Adirondacks, New York state, U.S. Small Island in Lower Saranac Lake.jpg
A small island in Lower Saranac Lake in the Adirondacks, New York state, U.S.
A view of the Uto Island at the Archipelago Sea in Pargas, Finland UtoK05.jpg
A view of the Utö Island at the Archipelago Sea in Pargas, Finland
Bangchuidao Island is an islet composed mostly of rock, in Dalian, Liaoning Province, China. Bangchuidao Island.JPG
Bangchuidao Island is an islet composed mostly of rock, in Dalian, Liaoning Province, China.
The islands of Fernando de Noronha, Brazil, are the visible parts of submerged mountains. Fernando noronha.jpg
The islands of Fernando de Noronha, Brazil, are the visible parts of submerged mountains.

An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. [1] Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. Sedimentary islands in the Ganges delta are called chars. A grouping of geographically or geologically related islands, such as the Philippines, is referred to as an archipelago.


There are two main types of islands in the sea: continental and oceanic. There are also artificial islands, which are man-made.


The word island derives from Middle English iland, from Old English igland (from ig or ieg, similarly meaning 'island' when used independently, and -land carrying its contemporary meaning; cf. Dutch eiland ("island"), German Eiland ("small island")). However, the spelling of the word was modified in the 15th century because of a false etymology caused by an incorrect association with the etymologically unrelated Old French loanword isle, which itself comes from the Latin word insula. [2] [3] Old English ieg is actually a cognate of Swedish ö and German Aue, and related to Latin aqua (water). [4]

Islets are very small islands.

Relationships with Continents

Differentiation from continents

Dymaxion world map with the continental landmasses (Roman numerals) and 30 largest islands (Arabic numerals) roughly to scale Fuller projection with largest islands.svg
Dymaxion world map with the continental landmasses (Roman numerals) and 30 largest islands (Arabic numerals) roughly to scale

There is no standard of size that distinguishes islands from continents, [5] [ page needed ] or from islets. [6]

There is a difference between islands and continents in terms of geology. [7] Continents are the largest landmass of a particular continental plate; this holds true for Australia, which sits on its own continental lithosphere and tectonic plate (the Australian Plate). [8]

By contrast, islands are either extensions of the oceanic crust (e.g. volcanic islands), or belong to a continental plate containing a larger landmass (continental islands); the latter is the case of Greenland, which sits on the North American Plate. [9]

Continental islands

Continental islands are bodies of land that lie on the continental shelf of a continent. [10] Examples are Borneo, Java, Sumatra, Sakhalin, Taiwan and Hainan off Asia; New Guinea, Tasmania, and Kangaroo Island off Australia; Great Britain, Ireland, and Sicily off Europe; Greenland, Newfoundland, Long Island, and Sable Island off North America; and Barbados, the Falkland Islands, and Trinidad off South America.

Microcontinental islands

A special type of continental island is the microcontinental island, which is created when a continent is rifted. Examples are Madagascar and Socotra off Africa, New Caledonia, New Zealand, and some of the Seychelles.


Another subtype is an island or bar formed by deposition of tiny rocks where water current loses some of its carrying capacity. This includes:

  • barrier islands, which are accumulations of sand deposited by sea currents on the continental shelves
  • fluvial or alluvial islands formed in river deltas or midstream within large rivers. While some are transitory and may disappear if the volume or speed of the current changes, others are stable and long-lived.

Oceanic islands

Tectonic versus volcanic

Oceanic islands are often considered to be islands that do not sit on continental shelves. Other definitions limit the term to only refer to islands with no past geological connections to a greater landmass. [11] The vast majority are volcanic in origin, such as Saint Helena in the South Atlantic Ocean. [12] The few oceanic islands that are not volcanic are tectonic in origin and arise where plate movements have lifted up the ocean floor above the surface. Examples are the Saint Peter and Saint Paul Archipelago in the North Atlantic Ocean and Macquarie Island in the South Pacific Ocean.

Volcanic islands


One type of volcanic oceanic island is found in a volcanic island arc. These islands arise from volcanoes where the subduction of one plate under another is occurring. Examples are the Aleutian Islands, the Mariana Islands, and most of Tonga in the Pacific Ocean. The only examples in the Atlantic Ocean are some of the Lesser Antilles and the South Sandwich Islands.

Oceanic Rifts

Another type of volcanic oceanic island occurs where an oceanic rift reaches the surface. There are two examples: Iceland, which is the world's second largest volcanic island, and Jan Mayen. Both are in the Atlantic.


A third type of volcanic oceanic island is formed over volcanic hotspots. A hotspot is more or less stationary relative to the moving tectonic plate above it, so a chain of islands results as the plate drifts. Over long periods of time, this type of island is eventually "drowned" by isostatic adjustment and eroded, becoming a seamount. Plate movement across a hot-spot produces a line of islands oriented in the direction of the plate movement. An example is the Hawaiian Islands, from Hawaii to Kure, which continue beneath the sea surface in a more northerly direction as the Emperor Seamounts. Another chain with similar orientation is the Tuamotu Archipelago; its older, northerly trend is the Line Islands. The southernmost chain is the Austral Islands, with its northerly trending part the atolls in the nation of Tuvalu. Tristan da Cunha is an example of a hotspot volcano in the Atlantic Ocean. Another hotspot in the Atlantic is the island of Surtsey, which was formed in 1963.


An atoll is an island formed from a coral reef that has grown on an eroded and submerged volcanic island. The reef rises to the surface of the water and forms a new island. Atolls are typically ring-shaped with a central lagoon. Examples are the Line Islands in the Pacific and the Maldives in the Indian Ocean.

Tropical islands

Plane landing on an airport island, Velana International Airport, Hulhule Island, Maldives Landing Runway 18 (2121588367).jpg
Plane landing on an airport island, Velana International Airport, Hulhulé Island, Maldives

Approximately 45,000 tropical islands with an area of at least 5 hectares (12 acres) exist. [13] Examples formed from coral reefs include Maldives, Tonga, Samoa, Nauru, and Polynesia. [13] Granite islands include Seychelles and Tioman.

The socio-economic diversity of tropical islands ranges from the Stone Age societies in the interior of North Sentinel, Madagascar, Borneo, and Papua New Guinea to the high-tech lifestyles of the city-islands of Singapore and Hong Kong. [14]

International tourism is a significant factor in the economy of many tropical islands including Seychelles, Sri Lanka, Mauritius, Réunion, Hawaii, Puerto Rico and the Maldives.


The process of de-islandisation is often concerning bridging, but there are other forms of linkages such as causeways: fixed transport links across narrow necks of water, some of which are only operative at low tides (e.g. that connecting Cornwall’s St Michael’s Mount to the peninsular mainland) while others (such as the Canso Causeway connecting Cape Breton to the Nova Scotia mainland), are usable all-year-round (aside from interruptions during storm surge periods). [15]

Some places may retain "island" in their names for historical reasons after being connected to a larger landmass by a land bridge or landfill, such as Coney Island and Coronado Island, though these are, strictly speaking, tied islands. Conversely, when a piece of land is separated from the mainland by a man-made canal, for example the Peloponnese by the Corinth Canal, more or less the entirety of Fennoscandia by the White Sea Canal, or Marble Hill in northern Manhattan during the time between the building of the United States Ship Canal and the filling-in of the Harlem River which surrounded the area, it is generally not considered an island.

Another type of connection is fostered by harbour walls/breakwaters that incorporate offshore islets into their structures, such as those in Sai harbour in northern Honshu, Japan, and the connection to the mainland which transformed Ilhéu do Diego from an islet. De-islanded through its fixed link to the mainland, the former islet’s name, Ilhéu do Diego, became functionally redundant (and thereby archaic) and the location took the fort as its namesake. [16] Some former island sites have retained designations as islands after the draining/subsidence of surrounding waters and their fixed linkage to land (England’s Isle of Ely and Vancouver’s Granville Island being respective cases in point). Their names are thereby archaic in that they reflect the islands’ pasts rather than their present structures and/or transport logistics. Other examples include Singapore and its causeway, and the various Dutch delta islands, such as IJsselmonde.

Artificial islands

Almost all of Earth's islands are natural and have been formed by tectonic forces or volcanic eruptions. However, artificial (man-made) islands also exist, such as the island in Osaka Bay off the Japanese island of Honshu, on which Kansai International Airport is located. Artificial islands can be built using natural materials (e.g., earth, rock, or sand) or artificial ones (e.g., concrete slabs or recycled waste). [17] [18]

Sometimes natural islands are artificially enlarged, such as Vasilyevsky Island in the Russian city of St. Petersburg, which had its western shore extended westward by some 0.5 km in the construction of the Passenger Port of St. Petersburg. [19]

Kansai International Airport, on an artificial island Kansai International Airport Aerial photograph.2007.jpg
Kansai International Airport, on an artificial island

Artificial islands are sometimes built on pre-existing "low-tide elevation," a naturally formed area of land which is surrounded by and above water at low tide but submerged at high tide. Legally these are not islands and have no territorial sea of their own. [20]

Island superlatives

See also

Related Research Articles

Archipelago Collection of islands

An archipelago, sometimes called an island group or island chain, is a chain, cluster, or collection of islands, or sometimes a sea containing a small number of scattered islands.

Lists of islands

This is a list of the lists of islands in the world grouped by country, by continent, by body of water, and by other classifications. For rank-order lists, see the other lists of islands below.

Geography of Iceland Geographical features of Iceland

Iceland is an island country at the confluence of the North Atlantic and Arctic oceans, east of Greenland and immediately south of the Arctic Circle, atop the constructive boundary of the northern Mid-Atlantic Ridge about 860 km (530 mi) from Scotland and 4,200 km (2,600 mi) from New York City. One of the world's most sparsely populated countries, Iceland's boundaries are almost the same as the main island – the world's 18th largest in area and possessing almost all of the country's area and population and also it is world's 9th largest island country. It is the westernmost European country and has more land covered by glaciers than in all of continental Europe. The total size is 103,125 km2 (39,817 sq mi). It has an exclusive economic zone of 751,345 km2 (290,096 sq mi).

Land bridge Connection between two land form bodies

In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea levels fall, exposing shallow, previously submerged sections of continental shelf; or when new land is created by plate tectonics; or occasionally when the sea floor rises due to post-glacial rebound after an ice age.

Hawaiian Islands Archipelago in the Pacific Ocean

The Hawaiian Islands are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaiʻi in the south to northernmost Kure Atoll. Formerly the group was known to Europeans and Americans as the Sandwich Islands, a name that James Cook chose in honor of the 4th Earl of Sandwich, the then First Lord of the Admiralty. Cook came across the islands by chance when crossing the Pacific Ocean on his Third Voyage, on board HMS Resolution; he was later killed on the islands on a return visit. The contemporary name of the islands, dating from the 1840s, is derived from the name of the largest island, Hawaiʻi Island.

North American Plate Large tectonic plate including most of North America, Greenland and part of Siberia

The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of 76 million km2 (29 million sq mi), it is the Earth's second largest tectonic plate, behind the Pacific Plate.

Volcanic arc Chain of volcanoes formed above a subducting plate

A volcanic arc is a chain of volcanoes formed above a subducting plate, positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally, volcanic arcs result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench. The oceanic plate is saturated with water, and volatiles such as water drastically lower the melting point of the mantle. As the oceanic plate is subducted, it is subjected to greater and greater pressures with increasing depth. This pressure squeezes water out of the plate and introduces it to the mantle. Here the mantle melts and forms magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone.

Large igneous province Huge regional accumulation of igneous rocks

A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive and extrusive, arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems.

In hydrology, an oceanic basin (or ocean basin) is anywhere on Earth that is covered by seawater. Geologically, ocean basins are large geologic basins that are below sea level.

Geology of Iceland

The geology of Iceland is unique and of particular interest to geologists. Iceland lies on the divergent boundary between the Eurasian plate and the North American plate. It also lies above a hotspot, the Iceland plume. The plume is believed to have caused the formation of Iceland itself, the island first appearing over the ocean surface about 16 to 18 million years ago. The result is an island characterized by repeated volcanism and geothermal phenomena such as geysers.

Geology of Chile

The geology of Chile is a characterized by processes linked to subduction such as volcanism, earthquakes and orogeny. The buildings blocks of Chile's geology assembled during the Paleozoic Era. Chile was by then the southwestern margin of the supercontinent Gondwana. In the Jurassic Gondwana began to split and the ongoing period of crustal deformation and mountain building known as the Andean orogeny began. In the Late Cenozoic Chile definitely separated from Antarctica, the Andes experienced a great rise accomplained by a cooling climate and the onset of glaciations.

Boundaries between the continents of Earth Overview of the boundaries between the continents of Earth

The boundaries between the continents of Earth are generally a matter of geographical convention. Several slightly different conventions are in use. The number of continents is most commonly considered seven but may range as low as four when Afro-Eurasia and the Americas are each considered a single continent. An island can be considered to be associated with a given continent by either lying on the continent's adjacent continental shelf or being a part of a microcontinent on the same principal tectonic plate. An island can also be entirely oceanic while still being associated with a continent by geology or by common geopolitical convention. Another example is the grouping into Oceania of the Pacific Islands with Australia and Zealandia.

Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin.

The following outline is provided as an overview of and introduction to Oceanography.

Zealandia Mostly submerged mass of continental crust containing New Zealand and New Caledonia

Zealandia, also known as Te Riu-a-Māui (Māori) or Tasmantis, is an almost entirely submerged mass of continental crust that subsided after breaking away from Gondwanaland 83–79 million years ago. It has been described variously as a submerged continent, a continental fragment, and a continent. The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995, and satellite imagery shows it to be almost the size of Australia. A 2021 study suggests Zealandia is 1 billion years old, about twice as old as geologists previously thought.

Continent Very large landmass identified by convention

A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven regions are: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Variations with fewer continents may merge some of these, for example some systems include Afro-Eurasia, the Americas or Eurasia as single continents. Zealandia, a largely submerged mass of continental crust, has also been described as a continent.

This is a list of articles related to plate tectonics and tectonic plates.


  1. Gillespie, Rosemary G.; Clague, David A., eds. (2009). Encyclopedia of Islands. University of California. pp. xxxi. ISBN   9780520256491.
  2. "Island". . Archived from the original on March 7, 2007. Retrieved March 5, 2007.
  3. Wedgwood, Hensleigh (1855). "On False Etymologies". Transactions of the Philological Society (6): 66.
  4. Ringe, Donald A. (2006). A Linguistic History of English: From Proto-Indo-European to Proto-Germanic. Oxford University Press. p. 109. ISBN   0-19-928413-X.
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  11. R. Zug, George (2013). Reptiles and Amphibians of the Pacific Islands: A Comprehensive Guide. University of California Press.
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  13. 1 2 Austrian Academy of Sciences (2002). "The Tropical Islands of the Indian and Pacific Oceans". Geographie. Austriaca. doi:10.1553/3-7001-2738-3.
  14. Arnberger, Hertha, Erik (2011). The Tropical Islands of the Indian and Pacific Oceans. Vienna: Austrian Academy of Sciences Press. ISBN   978-3-7001-2738-3.
  15. Bridging islands : the impact of fixed links. Godfrey Baldacchino. Charlottetown, P.E.I.: Acorn Press. 2007. ISBN   978-1-894838-24-5. OCLC   70884504.{{cite book}}: CS1 maint: others (link)
  16. Bicudo de Castro, Vincente; Hayward, Philip (2021). "The metamorphosis of Madeira's Ilhéu do Diego into Forte de São José, and the short-lived Principado do Ilhéu da Pontinha" (PDF). Transformations. 35: 40–51.
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  18. "What Makes an Island? Land Reclamation and the South China Sea Arbitration | Asia Maritime Transparency Initiative". July 15, 2015. Archived from the original on May 27, 2016. Retrieved June 28, 2016.
  19. "Conception of development of the artificial lands of Vasilievsky island". Archived from the original on September 25, 2016. Retrieved June 28, 2016.
  20. United Nations Convention on the Law of the Sea, Article 13. Archived from the original on September 2, 2017. Retrieved August 25, 2017.