Continent
A continent, by the standards most schoolchildren learn, is one of seven. Yet count the world's continents carefully and the answer slides anywhere from seven down to four. The English word itself once described the mainland of the Isle of Man and, in 1745, the island of Sumatra. Greenland spans 2,166,086 square kilometres and is called the largest island. Australia, at 7,617,930 square kilometres, is called the smallest continent. The difference between the two labels is not nature. It is agreement. Continents are identified by convention rather than by any strict rule, which means the map you trust is partly a habit. So where do the lines actually come from? Why is Europe a continent but India only a subcontinent? And who first dared to call a stretch of newly found land a fourth part of the world?
By convention, continents are understood to be large, continuous, discrete masses of land, ideally separated by expanses of water. Under that wording, every continent ought to be an island of some sort. The trouble is that in any scheme recognizing five or more continents, at least one pair is joined by land. The criterion of being large produces arbitrary results too, which is why the same body of water can be an island or a continent depending only on size. Earth's major landmasses share coasts on a single, continuous World Ocean. That one ocean gets divided into separate oceanic components by the continents and by geographic criteria, not the other way around. Geographers stretch the rules further by relaxing the demand for a discrete landmass. Africa and Asia meet at the Isthmus of Suez, while North America and South America join at the Isthmus of Panama. Both isthmuses are very narrow against the bulk of the lands they connect, and the Suez and Panama canals that cut them are shallow, narrow, and human-made.
The most restricted meaning of continent is simply the mainland, with the coastline and land borders forming its edge. In Britain, mainland Europe is called "the Continent," excluding islands such as Great Britain, Iceland, Ireland, and Malta. The continental United States covers the 49 states including Alaska but excluding Hawaii, plus the District of Columbia. Geology pushes the boundary outward to the continental shelf and the islands sitting on it. Because shorelines shift with sea level, the edge of the shelf becomes the true edge of the continent. Seen this way, Great Britain and Ireland belong to Europe, and Australia joins the island of New Guinea into one continent. Taken to its limit, this logic yields only three continents: Antarctica, Australia-New Guinea, and a single mega-continent linking Afro-Eurasia and America through the shelf around the Bering Sea. A cultural reading goes even further, folding in oceanic islands and fragments, so Iceland counts as Europe and Madagascar as Africa. Lower sea levels during the Pleistocene ice ages exposed shelf as dry land, fusing Tasmania to the Australian mainland to form a continent called Sahul.
Up to seven, or as few as four, depending on which boundaries you accept. The four-continent model keeps only continuous landmasses: Afro-Eurasia, America, Antarctica, and Australia. Merge Africa, Asia, and Europe into Afro-Eurasia, and combine the Americas, and four is what remains. The seven-continent model, taught across most English-speaking countries and in Bangladesh, China, India, Indonesia, Pakistan, the Philippines, Sri Lanka, and Suriname, keeps Asia and Europe and the two Americas apart. Greece and many Romance-speaking countries, including Latin America, teach a six-continent model that fuses the Americas. The Olympic flag's five rings stand for the five inhabited continents of that combined-America scheme, leaving out uninhabited Antarctica. Russia and parts of Eastern Europe use a different six, merging Asia and Europe into Eurasia. Some see that very split as a residue of Eurocentrism, noting that China and India each rival the whole European landmass rather than a single European country. By land area in the seven-continent model, Asia leads at 44,614,000 square kilometres and Oceania trails at 8,510,926 square kilometres, against a total land area of 149,733,926 square kilometres.
Christopher Columbus crossed the Atlantic to the Caribbean in 1492, yet across four voyages he never believed he had reached a new continent. He always thought it was part of Asia. In 1501, Amerigo Vespucci and Gonçalo Coelho sailed past Fernando de Noronha, trying to round what they took for the southern tip of Asia into the Indian Ocean. They followed the coast of Brazil and South America far past where Asia was known to reach, which told them this land had continental proportions. The account Mundus Novus, published under Vespucci's name in 1502 or 1503, credited him with the line, "I have discovered a continent in those southern regions that is inhabited by more numerous people and animals than our Europe, or Asia or Africa." In 1507, Martin Waldseemüller's world map Universalis Cosmographia became the first to show North and South America separated from Asia by water. His companion book Cosmographiae Introductio divided the earth into four parts and named the fourth "America," after Vespucci's first name, placing the word on South America.
New Holland was, to Samuel Butler in 1813, "an immense island, which some geographers dignify with the appellation of another continent." Europeans had reached Australia in 1606, but for a long time treated it as part of Asia. Only by the late 18th century did some call it a continent in its own right, and it was in the 1950s that Australia-as-continent finally replaced the older idea of Oceania as a great division. Antarctica was sighted in 1820 during the First Russian Antarctic Expedition. Charles Wilkes described it as a continent in 1838 on the United States Exploring Expedition, making it the last continent identified, though an antipodean landmass had been anticipated for millennia. An 1849 atlas labelled Antarctica a continent, yet few atlases followed suit until after World War II. Older still is the seven-continent idea in the Sanskrit Rig Veda, often dated to 1500 BCE, where the Earth is said to hold seven continents, and the Matsya Purana arranges them as seven concentric circles around Mount Meru.
Ancient Greek mariners drew the first division, naming Europe and Asia for the lands on either side of the Aegean Sea, the Dardanelles, the Sea of Marmara, the Bosporus, and the Black Sea. The names began at the coast and only later reached inland, where the geographers never found a convincing feature to split an indivisible Eurasia. Whether Africa, then called Libya, was part of Asia or a third part of the world became the next debate, and the three-part view won. Herodotus, in the 5th century BCE, objected to slicing Egypt between Asia and Africa and placed the boundary at Egypt's western border, counting Egypt as part of Asia. He also doubted dividing a single landmass into three at all, writing that Europe "stretches along both the others together, and it appears to me to be wider beyond all comparison." Eratosthenes, in the 3rd century BCE, noted geographers who split continents by rivers like the Nile and the Don, treating them as islands, and others who split them by isthmuses, calling them peninsulas. Pliny the Elder, in the 1st century CE, called Europe "by far the most beauteous portion of the earth." Herodotus's old query never died: it continues nearly two and a half millennia later.
Continental crust is only known to exist on Earth. To a geologist a continent is defined by that crust, a platform of metamorphic and igneous rocks largely of granitic composition, less dense and far thicker than oceanic crust. Being lighter, it floats higher on the dense underlying mantle, which is why continents stand as high platforms ringed by deep ocean basins. Four criteria pin one down: elevation above the ocean floor; a range of igneous, metamorphic, and sedimentary rock rich in silica; a crust thicker than its oceanic surroundings; and clear limits around an area of more than one million square kilometres. Some geologists go further and tie continents to cratons, stable cores untouched by mountain-building since the Precambrian. A craton's shield exposes crystalline basement rock typically 1.5 to 3.8 billion years old. With Zealandia added in 2017, Earth holds seven recognized geological continents: Africa, Antarctica, Australia, Eurasia, North America, South America, and Zealandia. Zealandia, surfacing mainly in New Zealand and New Caledonia, had its status disputed for a seeming lack of Precambrian rock, until a 2021 study found part of it Precambrian, twice as old as once thought. The historical geographer Martin W. Lewis pressed the human side of all this in his book The Myth of Continents: A Critique of Metageography.
Common questions
How many continents are there according to the Continent models?
The number of continents varies from as few as four to as many as seven. Most English-speaking countries recognize seven: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Fewer-continent models merge regions, such as Eurasia, the Americas, or Afro-Eurasia.
Why are Asia and Europe considered separate continents?
Asia and Europe sit on the continuous landmass of Eurasia but are kept apart for historical and cultural reasons. Europe is treated as a continent with about 10,180,000 square kilometres, while the Indian subcontinent, less than half that area, is called a subcontinent. Some view the Asia-Europe split as a residue of Eurocentrism.
Who named the continent of America?
Martin Waldseemüller named America in his 1507 book Cosmographiae Introductio, after Amerigo Vespucci's first name, placing the word on South America. His map Universalis Cosmographia was the first to show North and South America separated from Asia by water.
What is the difference between a continent and a microcontinent?
A continent is one of Earth's major landmasses, including dry land and continental shelves. Microcontinents are small continental fragments, such as Madagascar, that have rifted from a main landmass but are excluded from the continents because of their relatively small size.
When was Antarctica recognized as a continent?
Antarctica was sighted in 1820 during the First Russian Antarctic Expedition and described as a continent by Charles Wilkes in 1838 on the United States Exploring Expedition. It was the last continent identified, and an 1849 atlas labelled it a continent, though few atlases followed until after World War II.
How do geologists define a continent?
Geologists define a continent by continental crust and four criteria: elevation above the ocean floor, a range of igneous, metamorphic, and sedimentary rocks rich in silica, a crust thicker than oceanic crust, and clear limits around an area over one million square kilometres. With Zealandia added in 2017, Earth has seven recognized geological continents.