Definitions

island

island

[ahy-luhnd]
island, relatively small body of land surrounded entirely by water. (As the oceans form a continuous mass of water on the earth's surface, all continents are islands in the strict sense of the word.) The largest islands on earth are, in descending order of size, Greenland, New Guinea, Borneo, Madagascar, Baffin Island, Sumatra, Honshu (largest of the islands of Japan), and Great Britain. Depending on their origin, islands are either continental or oceanic. Continental islands are created by rise in sea level where only the summits of coastal highlands remain above water; or by the sea breaking through an isthmus or peninsula and cutting the land from the mainland. Typical continental islands are Great Britain and Martha's Vineyard. Other islands emerge along coasts as barrier islands, such as the Outer Banks, off North Carolina. Oceanic islands can result from volcanic islands rising above the water, especially on or near a mid-ocean ridge, as when the island of Surtsey appeared along the Mid-Atlantic Ridge S of Iceland in 1963. Island arcs, such as the Aleutian Islands, result from magmatic activity associated with the convergence of lithospheric plates (see plate tectonics). Oceanic islands may also be the emergent tips of volcanoes (seamounts) formed by hotspots. Oceanic islands that result from coral growth on the summit of seamounts are called coral islands or atolls (see coral reefs). These low islands only occur in tropical ocean areas. Oceanic islands are generally characterized by low faunal diversity, consisting of a few sea birds and insects. Vegetation is usually more abundant, as seeds are carried from remote lands by wind, water currents, and birds.

Long, curved chain of oceanic islands associated with intense volcanic and seismic activity and mountain-building processes. Examples include the Aleutian-Alaska Arc and the Kuril-Kamchatka Arc. Most island arcs consist of two parallel rows of islands. The inner row is a string of volcanoes, and the outer row is made up of nonvolcanic islands. In the case of single arcs, many of the islands are volcanically active. An island arc typically has a landmass or a partially enclosed, unusually shallow sea on its concave side. Along the convex side there usually exists a long, narrow deep-sea trench.

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Any area of land smaller than a continent and entirely surrounded by water. Islands may occur in oceans, seas, lakes, or rivers. A group of islands is called an archipelago. Continental islands are simply unsubmerged parts of a continental mass that are entirely surrounded by water; Greenland, the world's largest island, is of the continental type. Oceanic islands are produced by volcanic activity, when lava accumulates to enormous thickness until it finally protrudes above the ocean surface. The piles of lava that form Hawaii rise as high as 32,000 ft (9,700 m) above the ocean floor.

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Island, northeastern Russia. Located in the Arctic Ocean, it is crossed by the 180th meridian. It has an area of some 2,800 sq mi (7,300 sq km). Although it reaches an altitude of 3,596 ft (1,096 m) at Sovetskaya Mountain, there are no glaciers. The Russian explorer Ferdinand P. Wrangel, for whom the island was later named, determined its location from accounts of Siberian natives but did not land there during his mapping of the Siberian coast in the early 1820s. Russian fur traders subsequently visited the island, and it was sighted by U.S. vessels in 1867 and 1881. Survivors of a sunken Canadian ship reached Wrangel in 1914, and the leader of the expedition created an international incident in the early 1920s when he claimed Wrangel for Canada without authorization. The Soviet Union then annexed the island, and permanent occupation began in 1926. Wrangel Island State Reserve, established in 1976, occupies 1,730,000 ac (700,000 ha). The reserve was designated a UNESCO World Heritage site in 2004.

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Atoll, central Pacific Ocean. An unincorporated territory of the U.S., Wake Island comprises three low-lying coral islets (Wilkes, Peale, and Wake) that surround a lagoon and occupy a total land area of 2.5 sq mi (6.5 sq km). The atoll was claimed by the U.S. in 1899. In 1935 it became a stopover for transpacific commercial flights. The U.S. Navy began construction of an air and submarine base in 1939, which was half-completed when Wake was attacked and occupied by Japanese forces in December 1941. After the Japanese surrendered (1945), Wake was administered by the U.S. Air Force. Commercial flights resumed, but by 1974 Wake was being used as an emergency stopover. It is also the site of weather research stations. There is no indigenous population on the island, but there is a small contingent of civilian workers.

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Second largest island of the Arctic Archipelago, Canada. About 320 mi (515 km) long and 170–370 mi (270–600 km) wide, it has an area of 83,896 sq mi (217,291 sq km). Discovered in 1838 by Thomas Simpson, it was named for Queen Victoria and was first explored by John Rae in 1851. It is divided administratively between the Northwest Territories and the territory of Nunavut.

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Island (pop., 2001: 705,000) off southwestern British Columbia, Canada. It is the largest island (12,079 sq mi [31,285 sq km]) on the Pacific coast of North America. It has several peaks of more than 7,000 ft (2,100 m), as well as several fine harbours. The chief city is Victoria. It was inhabited by coastal Indians for several millennia before it was visited by early Spanish and English explorers, including Capt. James Cook in 1778. It was surveyed in 1792 by George Vancouver and was held by the Hudson's Bay Co. until it was made a British crown colony in 1849. It united with British Columbia in 1866. The island's main industries include lumbering, fishing, agriculture, and tourism.

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Nuclear power station near Harrisburg, Pa., site of the most serious accident in the history of the U.S. nuclear power industry (March 28, 1979). Mechanical failures and human errors caused a partial meltdown of the nuclear core and the release of radioactive gases. Despite assurances that there had been little risk to people's health, the accident increased public fears about the safety of nuclear power and strengthened public opposition to its use, effectively stopping construction of nuclear reactors and further development of U.S. nuclear power plants.

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Island in New York Harbor, a borough (pop., 2000: 443,728) of New York, New York, U.S. It has an area of almost 60 sq mi (155 sq km) and is connected to Brooklyn by the Verrazano-Narrows Bridge and to New Jersey by several bridges; it is accessible to Manhattan by the Staten Island Ferry. The Dutch attempted to colonize the island in 1630 but were thwarted by the Delaware Indian inhabitants until 1661, when the Dutch West India Co. granted the island to the French and settlements were established. Following the acquisition of New Netherland in 1664 by Great Britain, English and Welsh farmers established homes and farms on the island. As Richmond, it became a borough of New York City in 1898; Staten Island was made the official name in 1975. Mostly residential, the island has some industry, including shipbuilding yards, printing plants, and oil-storage tanks and refineries. It is the seat of Wagner College (1883, moved from Rochester in 1918).

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Island, Keewatin region, Nunavut, Canada. Lying at the entrance to Hudson Bay, the island is roughly triangular and has an area of 15,913 sq mi (41,214 sq km). Its plateau in the northeast, with 1,000-ft (300-m) coastal cliffs, gradually slopes to lowlands in the south. Its coastal waters are noted for Arctic char fishing.

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Island (pop., 2006: 1,022,316), larger and southernmost of the two principal islands of New Zealand. Separated from the North Island by Cook Strait, it has an area of 58,384 sq mi (151,215 sq km). Mountains, including the Southern Alps, occupy almost three-quarters of the island. Its main cities are Christchurch and Dunedin. Fiordland National Park in the southwest contains numerous coastal fjords and high lakes.

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Island (pop., including adjacent islands, 1996: 139,516), Fiji. Fiji's second largest island, it is 2,137 sq mi (5,535 sq km) in area. Sighted by the Dutch navigator Abel Janszoon Tasman in 1643, the volcanic Vanua Levu (meaning “Great Land”) has a central mountain range, culminating at Mount Nasorolevu (3,386 ft [1,032 m]), which divides the island into wet and dry sections. The chief river is the Ndreketi.

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One of the Galapagos Islands, eastern Pacific Ocean, Ecuador. It is the most populated and fertile island of the archipelago, producing sugar, coffee, cassava, and limes. Volcanic in origin and with an area of 195 sq mi (505 sq km), it is the only island of the group that has a regular supply of fresh water. Charles Darwin landed there at the settlement of San Cristóbal in 1835 and compiled data that he later used in his book On the Origin of Species (1859).

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Island, extreme eastern Russia. Together with the Kuril Islands, it forms an administrative region of Russia. It is 589 mi (948 km) long and a maximum of 100 mi (160 km) wide; it covers 29,500 sq mi (76,400 sq km). Sakhalin was first settled by Russians in 1853, and it came under Russian control in 1875 when Japan ceded it in exchange for the Kuril Islands. Japan held the southern part from 1905 to 1945, then ceded it and the Kurils to the U.S.S.R. The economy is dominated by fishing, lumbering, coal mining, and the extraction of oil and natural gas in the north.

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Island, off the North Carolina coast, U.S. Situated near the southern entrance to Albemarle Sound, the island is about 12 mi (19 km) long and 3 mi (5 km) wide. It was the site of the first English settlement in North America; its original colonists, sent by Walter Raleigh, arrived in mid-1585 but stayed only until 1586. A second group arrived in 1587; Virginia Dare, the first English child born in the Americas, was born on the island. When a supply ship arrived in 1590, all the colonists, including Virginia, had vanished; their fate is unknown. During the American Civil War the island was captured in 1862 by Union forces under Gen. Ambrose E. Burnside. It is now a resort and residential area.

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officially Rhode Island and Providence Plantations

State (pop., 2000: 1,048,319), northeastern U.S. One of the New England states and the smallest U.S. state, it covers 1,212 sq mi (3,139 sq km); its capital is Providence. Rhode Island is bordered by Massachusetts on the north and east, and Connecticut on the west. The Rhode Island Sound on the south is the basis of the state's fishing industry. The original inhabitants of the area were Narragansett Indians. The first European settlement was in 1636 by Roger Williams and his followers, who were banished from Massachusetts; in 1663 King Charles II granted a charter to Williams. Though it never officially joined the New England colonies in King Philip's War, it suffered greatly when many settlements were burned. It was at the forefront of the fight against British customs laws that led to the American Revolution. An original state of the Union, in 1790 it was the 13th state to ratify the Constitution, agreeing only after the Bill of Rights was included. The state's original charter remained in effect until Dorr's Rebellion (see Thomas W. Dorr) in 1842 led to extension of suffrage. The cotton-textile mill built by Samuel Slater in Pawtucket in 1790 initiated the Industrial Revolution in the U.S. Manufacturing is still important to the economy, and products include jewelry and silverware, textiles and clothing, and electrical machinery and electronics.

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Province (pop., 2006 est.: 135,851), Canada. One of the Maritime Provinces and Canada's smallest province, it is an island in the southern Gulf of St. Lawrence, separated from Nova Scotia and New Brunswick by the Northumberland Strait. Its capital is Charlottetown. Discovered by Jacques Cartier in 1534, it was used by Mi'kmaq (Micmac) Indians for fishing and hunting. It was colonized by the French in 1720, then ceded to the British in 1763. Known as the “Cradle of Confederation,” it was the site of the Charlottetown Conference of 1864, which led to the federation of Canada. It became a province in 1873. It has good natural harbours on its eastern and southern sides. There has been little industrial development, and more than half of the island is used for agriculture. Fishing and tourism are also of economic importance. In 1997 a bridge opened between Prince Edward Island and the mainland.

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Island (pop., 2003 est.: 47) and British overseas territory, south-central Pacific Ocean. It is the only inhabited island of the Pitcairn island group, which also includes Henderson, Ducie, and Oeno islands. It has an area of about 2 sq mi (5 sq km). Discovered in 1767 by the British, it was uninhabited until 1790, when it was settled by mutineers from HMS Bounty, led by Fletcher Christian. Pitcairn was annexed by Britain in 1838. The inhabitants were removed to Norfolk Island in 1856 because of overpopulation. Some returned to Pitcairn, and it is their descendants who make up the present population, subsisting on fishing and farming. In 1970 the British High Commissioner in New Zealand was appointed Pitcairn's governor.

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Barrier island, southern Texas, U.S. It is 113 mi (182 km) long and up to 3 mi (5 km) wide, lying along the Gulf Coast of Texas. It extends south from Corpus Christi to Port Isabel and is separated from the mainland by Laguna Madre. It contains a recreational preserve with a large variety of birdlife, excellent fishing, and a broad beach.

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Island (pop., 2006: 3,120,303), New Zealand. The smaller of the country's two principal islands, it is separated from South Island by the Cook Strait. It has an area of 44,702 sq mi (115,777 sq km). A large and growing majority of the population of New Zealand lives on North Island, concentrated in the cities of Wellington and Auckland.

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Norfolk Island pine (Araucaria excelsa).

Evergreen timber and ornamental conifer (Araucaria excelsa, or A. heterophylla) of the family Araucariaceae, native to Norfolk Island in the South Pacific Ocean. In nature this pine grows to a height of 200 ft (60 m), with a trunk sometimes reaching 10 ft (3 m) in diameter. The wood of large trees is used in construction, furniture, and shipbuilding. The sapling stage is grown worldwide as a houseplant and as an outdoor ornamental in regions with a Mediterranean climate. The monkey puzzle tree is a relative.

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Island territory (pop., 2006: 1,863) of Australia, southwestern South Pacific Ocean. Located midway between New Caledonia and New Zealand, the island has an area of 13 sq mi (34 sq km). Discovered by Capt. James Cook in 1774, it became a British penal colony (1788–1814, 1825–55). The population of Pitcairn Island was moved here in 1856, and many residents of Norfolk Island are descended from crew members of HMS Bounty. Of volcanic origin, it has generally rugged terrain with abundant Norfolk Island pine. The major industry is tourism.

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Island in the Timor Sea, off the coast of Northern Territory, Australia. It is 80 mi (130 km) long and 55 mi (88 km) wide, with an area of 2,240 sq mi (5,800 sq km). It was sighted by the Dutch navigator Abel Janszoon Tasman in 1644; the British built Fort Dundas there in 1824. Melville Island, known to Aborigines as Yermalner, is one of the few areas in Australia still occupied by its original Aboriginal peoples, the Tiwi, and in 1978 ownership of the island passed from the Australian government to the Tiwi Land Council.

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Body of water between the southern shore of Connecticut and the northern shore of Long Island, New York, U.S. It connects with the East River and with Block Island Sound. Covering 1,180 sq mi (3,056 sq km), it is 90 mi (145 km) long and 3–20 mi (5–32 km) wide. Its shores have many residential communities and summer resorts.

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Island (pop., 2000: 7,448,618), southeastern New York, U.S., lying between Long Island Sound and the Atlantic Ocean. It has four counties: Kings, Queens, Nassau, and Suffolk. Kings County (the borough of Brooklyn) and Queens County (the borough of Queens) form part of New York City. At its western end it is separated from the Bronx and Manhattan by the East River and from Staten Island by the Narrows. It is 118 mi (190 km) long, 12–23 mi (19–37 km) wide, and has an area of 1,401 sq mi (3,629 sq km). Its eastern portion has many beaches; it serves as a recreation area for New York City. Its southern shore, lined by sand spits (see Fire Island), shelters several bays, including Jamaica Bay. Originally inhabited by Indians (mostly Delaware), it was included in a grant to the Plymouth Co. It was settled by Dutch and English, but the whole island became part of the British colony of New York in 1664. It was the site of the Battle of Long Island (Aug. 27, 1776), an American defeat in the American Revolution.

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Island (pop., 2000: 13,913), Alaska, U.S. Lying in the Gulf of Alaska, it is 100 mi (160 km) long and 10–60 mi (16–96 km) wide and has an area of 3,588 sq mi (9,293 sq km). The Kodiak National Wildlife Refuge covers 75percnt of the island and is the habitat of the Kodiak bear. Discovered in 1763 by a Russian fur trader, the island, known as Kikhtak, became the site in 1784 of the first Russian colony in America. Russian control ended in 1867; the island was renamed Kodiak in 1901. In 1964 a destructive earthquake lowered the island by 5–6 ft (1.5–1.8 m).

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Island, South Australia. Located at the entrance to the Gulf St. Vincent, southwest of Adelaide, Kangaroo Island is 90 mi (145 km) long with an area of 1,680 sq mi (4,350 sq km). Visited in 1802 by the English explorer Matthew Flinders, it was named for its many kangaroos. Nepean Bay was the site of the state's first temporary settlement in 1836.

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Island, Galapagos Islands, Ecuador. It is the largest of the Galapagos Islands, located in the eastern Pacific Ocean west of mainland Ecuador. It has an area of 2,249 sq mi (5,825 sq km), and its northern tip, Albemarle, is crossed by the Equator. It has unique species of flightless cormorants and penguins as well as large numbers of iguanas and a flamingo colony.

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or Holy Island

Historic small island 2 mi (3 km) from the English Northumbrian coast. It became a religious centre in 635, when St. Aidan established a monastery and church there. It was abandoned in 875 because of the threat of Danish raids, but the monastery was refounded in 1082 and survived until the dissolution of the monasteries (1536–40) under Henry VIII. The manuscript of the Lindisfarne Gospels (circa 696–698) is one of the finest surviving illuminated manuscripts of the period. Lindisfarne's present-day parish church may occupy the site of St. Aidan's original monastery.

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Elongated sandspit, off the southern shore of Long Island, New York state, U.S. The island measures 32 mi (51 km) long and 0.5 mi (1 km) at its widest, and its name refers to fires that were built there as signals to ships during the War of 1812; a lighthouse was built at its western tip in 1858. Now a popular summer resort, it is connected to Long Island by two bridges and by ferry. Fire Island (now Robert Moses) State Park was opened in 1908, and a 19,000-acre (7,700-hectare) section of the island was dedicated as a national seashore in 1964.

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Island, Upper New York Bay, southeastern New York, U.S. It lies southwest of Manhattan island and has an area of about 27 acres (11 hectares). In 1808 the state of New York sold the island to the federal government. It served as the nation's major immigration station from 1892 until 1924, when immigrant processing was moved to New York City proper. It became part of the Statue of Liberty National Monument in 1965; its restored main hall is the site of the Ellis Island Immigration Museum.

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Island, Nunavut, Canada. The largest of the Queen Elizabeth Islands and lying off the northwestern coast of Greenland, it is believed to have been visited by Vikings in the 10th century AD. It is roughly 300 mi (500 km) wide by 500 mi (800 km) long, the most rugged in the Arctic Archipelago, with towering mountains and vast ice fields. Cape Columbia is the most northerly point of Canada. Ellesmere Island National Park Reserve (established 1986) became Quttinirpaaq National Park in 2001.

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Spanish Isla de Pascua native Rapa Nui

Sculptures cut from volcanic rock, Easter Island.

Island (pop., 2002: 3,791), eastern Pacific Ocean. Located 2,200 mi (3,600 km) west of Chile, it has an area of 63 sq mi (163 sq km). Initially inhabited circa AD 400 by Polynesians from the Marquesas, Easter Island has long been famous for its monolithic stone statues in human form. They are some 10–40 ft (3–12 m) high, the heaviest weighing about 82 tons. They were probably erected circa AD 1000–1600. War and disease decimated the island's population over the succeeding centuries, and the statues' origins were forgotten. Annexed by Chile in 1888, the island was designated a UNESCO World Heritage site in 1995.

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French Île du Diable

Rocky islet off the Atlantic coast of French Guiana. The smallest of the three Îles du Salut, it is a narrow strip of land 3,900 ft (1,200 m) long and 1,320 ft (400 m) wide. Part of a penal settlement since 1852, it housed the convicts' leper colony until the islands were made a maximum-security area. It shared the notoriety for cruelty of the mainland French Guiana penal colony. Spies and political prisoners, including Alfred Dreyfus, were held there. The island's use as a penal colony was phased out by the early 1950s.

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Amusement area, southern Brooklyn, N.Y., U.S. It was an island in the Atlantic Ocean until its creek silted up and it became part of Long Island. The first pavilion and bathhouse were erected in 1844, and it gained popularity with the coming of the subway in 1920. It has a 3.5-mi (5.6-km) boardwalk and an amusement park known for its roller coaster (the Cyclone). It is also the site of the New York Aquarium.

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Island, (pop., 2001: 109,330), eastern part of Nova Scotia, Canada. Separated from the mainland by the Strait of Canso, it is 110 mi (175 km) long and up to 75 mi (120 km) wide, with an area of 3,981 sq mi (10,311 sq km). It contains the Bras d'Or salt lakes. Originally called Île Royale as a French colony, it later took the name of its eastern cape, probably the first land visited by John Cabot on his 1497–98 voyage and probably named by Basque fishermen from Cap Breton, France. It was ceded to the British by the 1763 Treaty of Paris and joined to Nova Scotia. In 1784 it became a separate British crown colony, but it was rejoined to Nova Scotia in 1820. In 1955 the island was linked to the mainland by a causeway. Cape Breton Highlands National Park was established in 1936. Tourism is an important industry on the island.

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Island, Rhode Island, U.S. It lies at the eastern entrance to Long Island Sound, 9 mi (15 km) southwest of Point Judith, R.I. It has an area of about 11 sq mi (29 sq km) and is coextensive with the town of New Shoreham (pop., 2000: 1,010). Called Manisses by its original Indian inhabitants, Block Island (named for the Dutch explorer Adriaen Block) received its first European settlers in 1661 and was admitted to the colony of Rhode Island in 1664. Once dependent on fishing and farming, it is now primarily a resort.

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Island, Nunavut, Canada. Located in the Arctic Ocean between Cornwallis and Melville islands, it is 160 mi (260 km) long and 50–100 mi (80–160 km) wide. The coastline is fringed with islets, and several islands stretch from its western tip. Discovered in 1819 by Sir William Parry, it was named for Henry Bathurst, 3rd Earl Bathurst.

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Island, Northwest Territories, Canada. The westernmost island in the Canadian Arctic Archipelago, it lies northwest of Victoria Island and is separated from the mainland by Amundsen Gulf. About 250 mi (400 km) long, it has an area of 27,038 sq mi (70,028 sq km). First sighted by Sir William Parry's expedition in 1820, it was named for the naturalist Joseph Banks.

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Largest island in Canada and fifth largest island in the world (183,810 sq mi [476,068 sq km]), lying between Greenland and the Canadian mainland. Located west of Baffin Bay and the Davis Strait, it is administered as part of Nunavut territory. It was probably visited by Norse explorers in the 11th century. It was sighted by Martin Frobisher during his search for a Northwest Passage (1576–78). It is uninhabited except for a few coastal settlements. The world's northernmost mines are at Nanisvik. In 1972 Auyuittuq National Park was created on the eastern coast.

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An island or isle (/ˈaɪl/) is any piece of land that is completely surrounded by water in two dimensions, above high tide, and isolated from other significant landmasses. Very small islands such as emergent land features on atolls are called islets. A key or cay is another name for a small island or islet. An island in a river or lake may be called an eyot, /ˈaɪət/. There are two main types of islands: continental islands and oceanic islands. There are also artificial islands. A grouping of geographically and/or geologically related islands is called an archipelago.

The word island comes from Old English ī(e)gland (literally, "watery land"). However, the spelling of the word was modified in the 15th century by association with the etymologically unrelated Old French loanword isle.

There is no standard of size which distinguishes islands from islets and continents.

When defining islands as pieces of land that are completely surrounded by water, narrow bodies of water like rivers and canals are generally left out of consideration. For instance, in France the Canal du Midi connects the Garonne river to the Mediterranean Sea, thereby completing a continuous water connection from the Atlantic Ocean to the Mediterranean Sea. So technically, the land mass that includes the Iberian Peninsula and the part of France that is south of the Garonne River and the Canal du Midi is completely surrounded by water. For a completely natural example, the Orinoco River splits into two branches near Tamatama, in Amazonas state, Venezuela. The southern branch flows south and joins the Rio Negro, and then the Amazon. Thus, all of the Guianas (Guyana, Suriname, and French Guiana) and substantial parts of Brazil and Venezuela are surrounded by (river or ocean) water. These instances are not generally considered islands.

This also helps explain why Africa-Eurasia can be seen as one continuous landmass (and thus technically the biggest island): generally the Suez Canal is not seen as something that divides the land mass in two.

On the other hand, an island may still be described as such despite the presence of a land bridge, e.g., Singapore and its causeway or the various Dutch delta Islands, such as IJsselmonde. The retaining of the island description may therefore be to some degree simply due to historical reasons - though the land bridges are often of a different geological nature (for example sand instead of stone), and thus the islands remain islands in a more scientific sense as well.

Types

Continental islands

Continental islands are bodies of land that lie on the continental shelf of a continent. Examples include Greenland and Sable Island off North America; Barbados and Trinidad off South America; Great Britain, Ireland and Sicily off Europe; Sumatra and Java off Asia; and New Guinea, Tasmania and Kangaroo Island off Australia.

A special type of continental island is the microcontinental island, which results when a continent is rifted. Examples are Madagascar off Africa; the Kerguelen Islands; and some of the Seychelles.

Another subtype is an island or bar formed by deposition of tiny rocks where a water current loses some of its carrying capacity. An example is barrier islands, which are accumulations of sand deposited by sea currents on the continental shelf. Another example is islands in river deltas or in 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

Oceanic islands are ones that do not sit on continental shelves. They are volcanic in origin. One type of 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 include the Mariana Islands, the Aleutian Islands and most of Tonga in the Pacific Ocean. Some of the Lesser Antilles and the South Sandwich Islands are the only Atlantic Ocean examples.

Another type of 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 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 eroded and "drowned" by isostatic adjustment, 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 then extends 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 hot spot 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 include the Maldives in the Indian Ocean and Line Islands in the Pacific.

See also

References

External links

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