Boundaries between the continents
Determining the boundaries between the continents is generally a matter of geographical convention. Several slightly different conventions are in use. The number of continents is most commonly considered seven (in English-speaking countries) but may range as low as four when Afro-Eurasia and the Americas are both considered as single continents.[1] An island can be considered to be associated with a given continent by either lying on the continent's adjacent continental shelf (e.g. Singapore, the British Isles) or being a part of a microcontinent on the same principal tectonic plate (e.g. Madagascar and Seychelles). An island can also be entirely oceanic while still being associated with a continent by geology (e.g. Bermuda, the Australian Indian Ocean Territories) or by common geopolitical convention (e.g. Ascension Island, the South Sandwich Islands). Another example is the grouping into Oceania of the Pacific Islands with Australia and Zealandia.
There are three overland boundaries subject to definition:
While today the isthmus between Asia and Africa is navigable via the Suez Canal, and that between North and South America via the Panama Canal, these artificial channels are not generally accepted as continent-defining boundaries in themselves. The Suez Canal happens to traverse the Isthmus of Suez between the Mediterranean Sea and the Red Sea, dividing Africa and Asia. The continental boundaries are considered to be within the very narrow land connections joining the continents.
The remaining boundaries concern the association of islands and archipelagos with specific continents, notably:
Antarctica[edit]
Antarctica along with its outlying islands have no permanent population. All land claims south of 60°S latitude are held in abeyance by the Antarctic Treaty System.
Australia's Heard Island and McDonald Islands (an external territory) and the French Kerguelen Islands are located on the Kerguelen Plateau, on the Antarctic continental plate. Both are still within the bounds of the Indian Ocean. The United Nations categorizes Heard Island and McDonald Islands, which are politically affiliated with Australia, as being part of Oceania.[4] The islands are 4,000 km from Perth in Australia, and have never been inhabited by indigenous peoples of Oceania or any other humans. Heard Island has only been visited 240 times throughout its entire history, and the McDonald Islands have only ever been visited twice, in 1971 and 1980.[20][21] The World Factbook categorizes these islands as part of Antarctica rather than Oceania.[22]
The French Crozet Islands, Île Amsterdam, Île Saint-Paul, and the Norwegian Bouvet Island are also located on the Antarctic continental plate, and are not often associated with other continents. The United Nations categorize Bouvet Island as part of South America,[4] while the World Factbook categorizes it as part of Antarctica.[23]
South Georgia and the South Sandwich Islands are closer to Antarctica than to any other continent. However, they are politically associated with the Falkland Islands, which are less geographically isolated from South America. Furthermore, Argentina, a South American country, maintains its irredentist claims on all of these islands, which are administered by the United Kingdom. The United Nations consider them to be part of South America.[4] Definitions of South America that exclude the Galápagos Islands and Juan Fernández Islands (both oceanic in nature) still generally include the Falklands, which share biographical affinities to Patagonia and Tierra del Fuego, and which are located on the South American continental shelf.[24] The Falkland Islands and South Georgia and the South Sandwich Islands were uninhabited when discovered by Europeans, with some theorizing that the Falklands were visited by Indigenous peoples of the Americas during prehistoric times.[25][26] These theories are usually considered dubious, as there is no archaeological evidence indicating prehistoric human inhabitation on the Falklands.[27] South Georgia and the South Sandwich Islands do not have any permanent residents. The Falkland Islands have historically had a British population, with a culture distinct from that of mainland South America.[28] There was a violent war between Argentina and the United Kingdom regarding ownership of the islands in 1982, and the residents of the Falklands do not currently wish to be associated with South America, despite their geographical proximity.[27]
The Prince Edward Islands are located between Africa and Antarctica, and are the territory of South Africa, an African country.
Macquarie Island and the Antipodes Islands, Auckland Islands, and Campbell Islands are all uninhabited, and are located between Australia and New Zealand and Antarctica. The Antipodes Islands, Auckland Islands and Campbell Islands are politically part of New Zealand, while Macquarie Island has been integrated into the Australian state of Tasmania. None are discrete political entities like Heard Island and McDonald Islands. As such, they are likely considered by the United Nations also to be part of Oceania. The Auckland Islands could be considered part of Oceania on cultural grounds rather than mere political grounds, as they are believed to be the southernmost island group to have been settled by Polynesians during prehistoric times.[29] The islands were uninhabited when discovered by Europeans, but archaeological traces have since been found to indicate Polynesian settlement, dating to the 13th century, on Enderby Island. Macquarie Island is theorized to have possibly had contact with Polynesians, although there is no archaeological evidence to support this.[30][31]
Asia and North America[edit]
The Bering Strait and Bering Sea separate the landmasses of Asia and North America, as well as forming the international boundary between Russia and the United States. This national and continental boundary separates the Diomede Islands in the Bering Strait, with Big Diomede in Russia and Little Diomede in the U.S. The Aleutian Islands are an island chain extending westward from the Alaskan Peninsula toward Russia's Komandorski Islands and Kamchatka Peninsula. Most of them are always associated with North America, except for the westernmost Near Islands group, which is on Asia's continental shelf beyond the North Aleutians Basin and on rare occasions could be associated with Asia, which could then allow the U.S. state of Alaska to be considered a transcontinental state. The Aleutian Islands are sometimes associated with Oceania, owing to their status as remote Pacific islands, and their proximity to the Pacific Plate.[110][111][112] This is extremely rare, however, because of their non-tropical biogeography and because their inhabitants have historically been related to Indigenous Americans.[60][34]
St. Lawrence Island in the northern Bering Sea belongs to Alaska and may be associated with either continent but is almost always considered part of North America, as with the Rat Islands in the Aleutian chain. At their nearest points, Alaska and Russia are separated by only 4 kilometres (2.5 miles).
Europe and North America[edit]
The geographical notion of a continent stands in opposition to islands and archipelagos.[113][114] Nevertheless, there are some islands that are considered part of Europe in a political sense. This most notably includes the British Isles (part of the European continental shelf and during the Ice Age of the continent itself); the islands of the North Sea, the Baltic Sea, and the Mediterranean that are part of the territory of a country situated on the European mainland; the Azores on the Mid-Atlantic Ridge, part of Portugal; and usually also the island states of Iceland (part of Norway and/or Denmark from 13th to early 20th centuries) and Malta.
The Norwegian islands of Jan Mayen and Svalbard in the Arctic Ocean are usually associated with Europe.
South of the Arctic, Europe and North America are separated by the North Atlantic. In terms of associating its oceanic islands with either continent, the boundary is usually drawn between Greenland and Iceland and between Bermuda and the Azores' Grupo Ocidental (Western Group)—all other North Atlantic islands are continental. Iceland and the Azores are protrusions of the Mid-Atlantic Ridge and are associated with and peopled from Europe, even though they have areas on the North American Plate. (Definitions of "continents" are a physical and cultural construct dating back centuries, long before the advent or even knowledge of plate tectonics; thus, defining a "continent" falls into the realm of physical and cultural geography (i.e. geopolitics), while continental plate definitions fall under plate tectonics in the realm of geology.) Some definitions of the Europe – America continental boundary place it on (the northern half of) the Mid-Atlantic Ridge, which would make Iceland a transcontinental country.
Greenland is geographically part of North America. Politically, however, it is more associated with Europe as it is part of the Kingdom of Denmark, although it has extensive home rule and EU law no longer applies there. The United Nations consider Greenland to be part of North America; this is unusual, as the United Nations categorize many nations and territories purely on political convention rather than geographical or cultural convention.[4] The Greenland national football team, while not officially part of any confederation, has historically competed against teams from Europe, rather than North America.
Three islands in the Caribbean are legally a direct part of the Netherlands, that is the Caribbean Netherlands (Bonaire, Saba and Sint Eustatius). Two islands in the Caribbean are legally a direct part of France, Guadeloupe and Martinique.