Both of these isthmuses are very narrow compared to the bulk of the landmasses they unite. In both cases, there is no complete separation of these landmasses by water (disregarding the Suez Canal and Panama Canal, which are both narrow and shallow, as well as man-made). Asia and Africa are joined by the Isthmus of Suez, and North and South America by the Isthmus of Panama. Several continents are defined not as absolutely distinct bodies but as " more or less discrete masses of land". Of the seven most globally recognized continents, only Antarctica and Australia are completely separated from other continents by the ocean.
The criterion that each continent is a discrete landmass is commonly relaxed due to historical conventions and practical use. See also: List of transcontinental countries In this sense the islands of Great Britain and Ireland are part of Europe, while Australia and the island of New Guinea together form a continent. įrom this perspective, the edge of the continental shelf is the true edge of the continent, as shorelines vary with changes in sea level. Similarly, the continental United States refers to the 48 contiguous states and the District of Columbia and may include Alaska in the northwest of the continent (the two being separated by Canada), while excluding Hawaii in the Pacific Ocean.įrom the perspective of geology or physical geography, continent may be extended beyond the confines of continuous dry land to include the shallow, submerged adjacent area (the continental shelf) and the islands on the shelf ( continental islands), as they are structurally part of the continent. In this sense, the term continental Europe (sometimes referred to in Britain as "the Continent") is used to refer to mainland Europe, excluding islands such as Great Britain, Iceland, Ireland, and Malta while the term continent of Australia may refer to the mainland of Australia, excluding New Guinea, Tasmania, and other nearby islands. The most restricted meaning of continent is that of a continuous area of land or mainland, with the coastline and any land boundaries forming the edge of the continent. The criterion "large" leads to arbitrary classification: Greenland, with a surface area of 2,166,086 square kilometres (836,330 sq mi), is only considered the world's largest island, while Australia, at 7,617,930 square kilometres (2,941,300 sq mi), is deemed the smallest continent.Įarth's major landmasses all have coasts on a single, continuous World Ocean, which is divided into a number of principal oceanic components by the continents and various geographic criteria. In modern schemes with five or more recognised continents, at least one pair of continents is joined by land in some way. It postulates that the current continents formed from the breaking up of a supercontinent Pangaea that formed hundreds of millions of years ago.įurther information: Island § Differentiation from continentsīy convention, continents "are understood to be large, continuous, discrete masses of land, ideally separated by expanses of water".
The idea of continental drift gained recognition in the 20th century. Continental crust is only known to exist on Earth. The geological continents correspond to six large areas of continental crust that are found on the tectonic plates, but exclude small continental fragments such as Madagascar that are generally referred to as microcontinents. In geology, a continent is defined as "one of Earth's major landmasses, including both dry land and continental shelves". Under this scheme, most of the island countries and territories in the Pacific Ocean are grouped together with the continent of Australia to form a geographical region called Oceania. Oceanic islands are frequently grouped with a nearby continent to divide all the world's land into geographical regions. Zealandia, a largely submerged mass of continental crust, has also been described as a continent. Variations with fewer continents may merge some of these, for example America, Eurasia, or Afro-Eurasia are sometimes treated as single continents, which can bring the total number as low as four. Ordered from largest in area to smallest, these seven regions are: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Depending on the convention and model, some continents may be consolidated or subdivided: for example, Eurasia is most often subdivided into Asia and Europe (red shades), while North and South America are sometimes recognised as one American continent (green shades)Ī continent is any of several large landmasses. Animated, colour-coded map showing the various continents.
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