Boundaries between continents

Color-coded map of continents:
          Americas
        North America
        South America
               Afro-Eurasia
        Africa
             Eurasia
           Asia
           Europe
     Antarctica
     Australasia/Oceania

Map of island countries: these states are not located on any continent (landmass), but they are usually grouped geographically with a neighbouring continent

A map of transcontinental countries, countries that control territory in more than one continent.

  Contiguous transcontinental countries.

  Non-contiguous transcontinental countries.

  Countries that could be considered transcontinental depending on definitions and claim legality.

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 the Americas and Afro-Eurasia are each considered a single continent. According to the definition of a continent in the strict sense, an island cannot be part of any continent, but by convention and in practice most major islands are associated with a continent.

There are three overland boundaries subject to definition:

• between Europe and Asia (dividing Eurasia): along the Turkish Straits, the Caucasus and the Urals (historically also north of the Caucasus, along the Kuma–Manych Depression or along the Don River)
• between Asia and Africa (dividing Afro-Eurasia into Africa and Eurasia): at the Isthmus of Suez
• between North America and South America (dividing the Americas): the Isthmus of Panama

While the isthmus between Asia and Africa and that between the two Americas are today navigable, via the Suez and Panama canals, man-made diversions and canals are generally not accepted on their own accord as continent-defining boundaries; the Suez Canal happens to traverse the isthmus between the Mediterranean Sea and Red Sea, dividing Asia and Africa. The remaining boundaries concern the association of islands and archipelagos with specific continents, notably:

• the delineation of Southeast Asia from Australasia
• the delineation between Africa, Europe and Asia in the Mediterranean Sea
• the delineation between Asia and Europe in the Arctic Ocean
• the delineation between Europe and North America in the Atlantic Ocean
• the delineation between North and South America in the Caribbean Sea
• the delineation of Asia from North America in the North Pacific Ocean

Europe and Africa

The Mediterranean Sea

The Atlantic Ocean around the boundary

The European and African mainlands are non-contiguous, and the delineation between these continents is thus merely a question of which islands are to be associated with which continent.

The Portuguese Atlantic island possession of the Azores is 1,368 km (850 mi) from Europe, 1,507 km (936 mi) from Africa, and is usually grouped with Europe if grouped with any continent. By contrast, the Canary and Madeira islands off the Atlantic coast of Morocco are much closer to and usually grouped with Africa (Madeira is 860 km (530 mi) from Europe and 660 km (410 mi) from Africa).

The island nation of Malta is approximately 81 km (50 mi) from the coast of Sicily in Europe - much closer than the 288 km (179 mi) distance to the closest African coast. The nearby Italian island of Lampedusa is 207 km (129 mi) from Sicily while just 127 km (79 mi) from the African coast; similarly, Pantelleria is 100 km (62 mi) from Sicily and just 71 km (44 mi) from the African coast. All are generally included within Europe if grouped with any continent at all.

Europe and Asia

Modern definition

Since there is no significant geographical separation between Europe and Asia, the border between the two is largely an arbitrary, historical, and cultural construct. An often cited definition of the Europe-Asia border is said to follow the Aegean Sea, the Turkish Straits, the Black Sea, along the watershed of the Greater Caucasus, the northwestern portion of the Caspian Sea and along the Ural River and Ural Mountains to the Arctic Ocean. These delineations, however, are not definitive. For instance, the National Geographic places Cyprus entirely in Asia but the country is nevertheless a member of the European Union. Similarly, although Georgia lies on the arbitrary Europe-Asia border, it is generally considered to be part of Europe.

Member states of the Council of Europe

The Turkish city Istanbul lies on both sides of the Bosporus (one of the Turkish Straits), making it a transcontinental city. Russia and Turkey are transcontinental countries with territory in both Europe and Asia by any definition except that of Eurasia as a single continent. While Russia is historically a European country with a history of imperial conquests in Asia, the situation for Turkey is inverse, as that of an Asian country with imperial conquests in Europe. Kazakhstan is also a transcontinental country by this definition, its West Kazakhstan and Atyrau provinces extending on either side of the Ural River.

This Ural River delineation is the only segment not to follow a major mountain range or wide water body, both of which often truly separate populations. However, the Ural River is the most common division used by authorities, is the most prominent natural feature in the region, and is the "most satisfactory of those (options) proposed" which include the Emba River, a much smaller stream cutting further into Central Asian Kazakhstan. The Ural River bridge in Orenburg is even labeled with permanent monuments carved with the word "Europe" on one side, "Asia" on the other.

The Kuma–Manych Depression (more precisely, the Manych River, the Kuma–Manych Canal and the Kuma River) remains cited less commonly as one possible natural boundary in contemporary sources. This definition peaked in prominence in the 1800s, however it has declined in usage since then, as it places traditionally European areas of Russia such as Stavropol, Krasnodar, and even areas just south of Rostov-on-Don in Asia.

Historical variations

The threefold division of the Old World into Europe, Asia and Africa has been in use since the 6th century BC, due to Greek geographers such as Anaximander and Hecataeus. The boundary between Europe and Asia is somewhat unique among continental boundaries because of its largely mountain-and-river-based characteristics north and east of the Black Sea. Europe can be considered more of a subcontinent within Eurasia in de facto terms, and it has sometimes been referred to as such.

Anaximander placed the boundary between Asia and Europe along the Phasis River (the modern Rioni) in the Caucasus (from its mouth by Poti on the Black Sea coast, through the Surami Pass and along the Kura River to the Caspian Sea), a convention still followed by Herodotus in the 5th century BC. As geographic knowledge of the Greeks increased during the Hellenistic period, this archaic convention was revised, and the boundary between Europe and Asia was now considered to be the Tanais (the modern Don River). This is the convention used by Roman era authors such as Posidonius, Strabo and Ptolemy.

Road sign on the continental border between Europe and Asia near Magnitogorsk, Russia. It reads "Europe", above a crossed-out "Asia", as one enters Europe and leaves Asia.

Throughout the Middle Ages and into the 18th century, the traditional division of the landmass of Eurasia into two continents, Europe and Asia, followed Ptolemy, with the boundary following the Turkish Straits, the Black Sea, the Kerch Strait, the Sea of Azov and the Don (ancient Tanais). But maps produced during the 16th to 18th centuries tended to differ in how to continue the boundary beyond the Don bend at Kalach-na-Donu (where it is closest to the Volga, now joined with it by the Volga–Don Canal), into territory not described in any detail by the ancient geographers.

Philip Johan von Strahlenberg in 1725 was the first to depart from the classical Don boundary by drawing the line along the Volga, following the Volga north until the Samara Bend, along Obshchy Syrt (the drainage divide between Volga and Ural) and then north along Ural Mountains. The mapmakers continued to differ on the boundary between the lower Don and Samara well into the 19th century. The 1745 atlas published by the Russian Academy of Sciences has the boundary follow the Don beyond Kalach as far as Serafimovich before cutting north towards Arkhangelsk, while other 18th- to 19th-century mapmakers such as John Cary followed Strahlenberg's prescription. To the south, the Kuma–Manych Depression was identified circa 1773 by a German naturalist Peter Simon Pallas as a valley that, once upon a time, connected the Black Sea and the Caspian Sea, and subsequently was proposed as a natural boundary between continents.

By the mid-19th century, there were three main conventions, one following the Don, the Volga–Don Canal and the Volga, the other following the Kuma–Manych Depression to the Caspian and then the Ural River, and the third abandoning the Don altogether, following the Greater Caucasus watershed to the Caspian. The question was still treated as a "controversy" in geographical literature of the 1860s, with Douglas Freshfield advocating the Caucasus crest boundary as the "best possible", citing support from various "modern geographers".

Islands

Cyprus is an island of the Mediterranean located close to Asia Minor, so that it is usually associated with Asia and/or the Middle East, as in the World Factbook, but the Republic of Cyprus was nevertheless admitted to the Council of Europe in 1961 and joined the EU in 2004. The northern part of the island functions as the unrecognized (except by Turkey) Turkish Republic of Northern Cyprus.

The Greek North Aegean Islands and the Dodecanese lie on the coast of the Asian part of Turkey (on the Asian continental shelf).

Europe and North America

Europe and North America are separated by the North Atlantic. In terms of associating islands with either continent, the boundary is usually drawn between Greenland and Iceland. The Norwegian islands of Jan Mayen and Svalbard in the Arctic Ocean are usually associated with Europe. 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; i.e., defining a "continent" falls into the realm of physical and cultural geography, while continental plate definitions fall under plate tectonics in the realm of geology.)

Islands

The geographical notion of a continent stands in opposition to islands and archipelagos. 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), besides the islands of the North Sea, the Baltic Sea and the Mediterranean which are part of the territory of a country situated on the European mainland, and usually also the island states of Iceland and Malta.

Russia's Vaygach Island and Novaya Zemlya extend northward from the northern end of the Ural Mountains and are a continuation of that chain into the Arctic Ocean. While Novaya Zemlya was variously grouped with Europe or with Asia in 19th-century maps, it is now usually grouped with Europe, the continental boundary considered to join the Arctic Ocean along the southern shore of the Kara Sea. The Russian Arctic archipelago of Franz Josef Land farther north is also associated with Europe.

Europe ends in the west at the Atlantic Ocean, although Iceland and the Azores archipelago (in the Atlantic, between Europe and North America) are usually considered European, as is the Norwegian Svalbard archipelago in the Arctic Ocean. Greenland is geographically part of North America, but politically 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.

Africa and Asia

  African part of Egypt

  Asian part of Egypt

  Rest of Asia

  Rest of Africa

Historically, in Greco-Roman geography, Africa (Libya) was taken to begin in Marmarica, at the Catabathmus Magnus, placing Egypt in Asia entirely. The idea of Egypt being an "African" country seems to develop in around the mid 19th century; the term Africa was classically reserved for what is now known as the Maghreb, to the explicit exclusion of Egypt, but with the exploration of Africa the shape of the African landmass (and Egypt's "natural" inclusion in that landmass) became apparent. In 1806, William George Browne still titled his travelogue Travels in Africa, Egypt, and Syria. Similarly, James Bruce in 1835 published Travels through part of Africa, Syria, Egypt, and Arabia. On the other hand, as early as 1670 John Ogilby under the title Africa published "an accurate Description of the Regions of Egypt, Barbary, Libya, and Billedulgerid, the Land of Negroes, Guinea, Æthiopia, and the Abyssines, with all the adjacent Islands, either in the Mediterranean, Atlantic, Southern, or Oriental Seas, belonging thereunto".

The usual line taken to divide Africa from Asia today is at the Isthmus of Suez, the narrowest gap between the Mediterranean and Gulf of Suez, the route today followed by the Suez Canal. This makes the Sinai Peninsula geographically Asian, and Egypt a transcontinental country.

Less than 2% of Egyptian population live in the Sinai, and hence Egypt even though technically transcontinental is usually considered an African country. But when discussing the geopolitical region of the Middle East and North Africa, Egypt is usually grouped with the Asian countries as part of the Middle East, while Egypt's western neighbor Libya is grouped with the remaining North African countries as the Maghreb.

The Seychelles, Mauritius, and Comoros are island nations in the Indian Ocean associated with Africa. The island of Socotra may be considered African as it lies on this continent's shelf, but is part of Yemen, an Asian country.

North and South America

Panama

Further information: Americas and Central America

Mainland

The border between North America and South America is at some point on the Isthmus of Panama. The most common demarcation in atlases and other sources follows the Darién Mountains watershed divide along the Colombia-Panama border where the isthmus meets the South American continent. Virtually all atlases list Panama as a state falling entirely within North America and/or Central America.

Islands

Often most of the Caribbean islands are considered part of North America, but Aruba, Bonaire, Curaçao and Trinidad and Tobago lie on the continental shelf of South America. On the other hand, the Venezuelan Isla Aves and the Colombian San Andrés and Providencia lie on the North American shelf.

Asia and North America

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 US. The Aleutian Islands are an island chain extending westward from the Alaska 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 which would make Russia the world's only doubly transcontinental country or the only country that borders more than two countries or borders three continents.

St. Lawrence Island in the northern Bering Sea belongs to Alaska and may be associated with either continent but are almost always considered part of North America, as with the Rat Islands in the Aleutian chain.

The Americas and Oceania

The Galápagos Islands and Malpelo Island in the eastern Pacific Ocean are possessions of Ecuador and Colombia, respectively, and associated with South America. The uninhabited French possession of Clipperton Island 600 miles (970 km) off the Mexican coast is associated with North America.

Easter Island, a territory of Chile, is considered to be in Oceania, though politically it is associated with South America.

The United States controls numerous territories in Oceania, including the state of Hawaii.

Asia and Oceania

Wallace, Lydekker and Weber Lines, the principals on Melanesia

Indonesia is today more commonly referred to as one of the Southeast Asian countries, and thus simply Asian. However, the Malay Archipelago is sometimes divided between Asia and Australasia, usually along the anthropologic Melanesian line or Weber's Line. Indonesia controls the western half of New Guinea, geographically part of Australasia. The eastern half of the island is part of Papua New Guinea which is considered to be part of the Pacific. East Timor, an independent state that was formerly a territory of Indonesia, which is geographically part of Asia, is classified by the United Nations as part of the "South-Eastern Asia" block. It is expected to join the Association of Southeast Asian Nations, having been involved as an ASEAN Regional Forum member since independence, and has participated in the Southeast Asian Games since 2003. Occasionally, all of the Malay Archipelago is included in Oceania, although this is extremely rare, especially as most of the archipelago lies on the Asian continental shelf.

The Commonwealth of Australia includes island possessions in Oceania and islands closer to Indonesia than the Australian mainland.

Antarctica

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.

The South Georgia and the South Sandwich Islands are closer to Antarctica than to any other continent. However, they are politically associated with the inhabited Falkland Islands which are closer to South America. Furthermore, Argentina, a South American country, maintains its irredentist claims on the islands. The continental shelf boundary separates the two island groups.

The Prince Edward Islands are located between Africa and Antarctica, and are the territory of South Africa, an African country. The Australian Macquarie Island and the New Zealand Antipodes Islands, Auckland Islands, and Campbell Islands, are all located between the Oceanian countries of Australia and New Zealand and Antarctica.

Australia's Heard Island and McDonald Islands and the French Kerguelen Islands are located on the Kerguelen Plateau, on the Antarctic continental plate. 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.

See also

• List of countries bordering on two or more oceans
• List of transcontinental countries
• List of sovereign states and dependent territories by continent
• Continental divide
• Borders of the oceans