A continent (Latin continere, "to hold together") is a large continuous mass of land on the planet Earth.
There is no single standard for what defines a continent, and therefore various cultures and sciences have different lists of what are considered to be continents. In general, a continent must be large in area, consist of non-submerged land, and have geologically significant borders. While some consider that there are as few as four or five continents, the most commonly used counts are six or seven.
Two of the largest disagreements in listing continents are whether Europe and Asia should be considered separately or combined into Eurasia, and whether North America and South America should be considered separately or combined into America. A few geographers have also suggested grouping Europe, Asia, and Africa into a continent of Eurafrasia (see Africa-Eurasia).
The seven continent model is taught in the United States, while the six continent (combined Eurasia) model is also taught in North America. The five continent (combined Americas, no Antartica) model is commonly taught in Europe and South America including United Kingdom and Mexico. The continents of the "five continents" model (as shown by the five Olympic Games flag rings) are speculated to be the five permamently populated continents (viewing Antarctica as only temporarily populated, and all the Americas as one).
Continents are sometimes conceptually combined to make "supercontinents" or subdivided to make "subcontinents". These terms are even less precisely defined than "continent" itself.
Islands are usually considered to "belong" to the continent they are closest to, and hence the British Isles are considered to be a part of Europe. "Oceania" is sometimes used to refer collectively to Australia and the Pacific islands, including New Zealand. Other times, Australia is considered to be a continent (possibly including New Zealand), and the other Pacific islands are not associated with any continent.
When "the Continent" is referred to without clarification by a speaker of British English, it is usually presumed to mean Continental Europe, i.e., Europe, explicitly excluding Great Britain and Ireland. Similarly, when the term "the Subcontinent" is used, it is presumed to refer to India.
See also List of countries by continent, Satellite Images of Continents.
Some systems of defining continents
- Seven Continents: Africa, Antarctica, Asia, Europe, North America, Oceania, South America.
- Seven Continents: Africa, Antarctica, Asia, Europe, North America, Australia, South America.
- Six Continents: Africa, Antarctica, Oceania, Eurasia, North America, and South America.
- Six Continents: Africa, America, Antarctica, Asia, Oceania, and Europe.
- Five Continents: Africa, America, Oceania, Antarctica, Eurasia.
- Five Continents: Africa, America, Oceania, Europe, Asia.
- Four Continents: America, Oceania, Antarctica, Eurafrasia.
During the 20th century, it became accepted by geologists that continents move location on the face of the planet over the geologic timescale, a process known as continental drift, explained by the theory of plate tectonics.
The surface of the Earth currently consists of seven major and many minor tectonic plates, and it is these that have drifted, broken apart and joined together over time to give rise to the continents we now recognize. Consequently, in the geological past and prior to the present continents, other continents existed - see Category:Historical continents.