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. An island can be considered to be associated with a given continent by either lying on the continent's adjacent continental shelf (e.g.
A T and O map or O–T or T–O map (orbis terrarum, orb or circle of the lands; with the letter T inside an O), also known as an Isidoran map, is a type of early world map that represents the physical world as first described by the 7th-century scholar Isidore of Seville in his De Natura Rerum and later his Etymologiae. Although not included in the original Isidorian maps, a later manuscript added the names of Noah's sons (Sem, Iafeth and Cham) for each of the three continents (see Biblical terminology for race).
Zealandia (pronounced ziːˈlændiə), also known as Te Riu-a-Māui (Māori) or Tasmantis, is an almost entirely submerged mass of continental crust in Oceania that subsided after breaking away from Gondwanaland 83–79 million years ago. It has been described variously as a submerged continent, continental fragment, and microcontinent. The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995, and satellite imagery shows it to be almost the size of Australia.
Afro-Eurasia (also Afroeurasia, Eurafrasia, Africa-Eurasia or the Old World) is a landmass comprising the continents of Africa, Asia, and Europe. The terms are compound words of the names of its constituent parts. Its mainland is the largest and most populous contiguous landmass on Earth. Afro-Eurasia encompasses , 57% of the world's land area, and has a population of approximately 6.7 billion people, roughly 86% of the world population.
The continent of Australia, sometimes known in technical contexts by the names Sahul (səˈhuːl), Australia-New Guinea, Australinea, Meganesia, or Papualand to distinguish it from the country of Australia, is located within the Southern and Eastern hemispheres. The name "Sahul" takes its name from the Sahul Shelf, which is a part of the continental shelf of the Australian continent. The continent includes mainland Australia, Tasmania, the island of New Guinea (Papua New Guinea and Western New Guinea), the Aru Islands, the Ashmore and Cartier Islands, most of the Coral Sea Islands, and some other nearby islands.
The Wilson Cycle is a model that describes the opening and closing of ocean basins and the subduction and divergence of tectonic plates during the assembly and disassembly of supercontinents. A classic example of the Wilson Cycle is the opening and closing of the Atlantic Ocean. It has been suggested that Wilson cycles on Earth started about 3 Ga in the Archean Eon. The Wilson Cycle model was a key development in the theory of plate tectonics during the Plate Tectonics Revolution.
An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large in area and is either completely surrounded by dry land or connected to an ocean by a river, strait or "arm of the sea". An inland sea will generally have higher salinity than a freshwater lake, but usually lower salinity than seawater. As with other seas, inland seas experience tidality governed by the orbits of the Moon and Sun. What constitutes an "inland sea" is complex and somewhat necessarily vague.
A landmass, or land mass, is a large region or area of land that is in one piece and not broken up by oceans. The term is often used to refer to lands surrounded by an ocean or sea, such as a continent or a large island. In the field of geology, a landmass is a defined section of continental crust extending above sea level. Continents are often thought of as distinct landmasses and may include any islands that are part of the associated continental shelf.
In geography, the antipode (ˈæntɪˌpoʊd,_ænˈtɪpədi) of any spot on Earth is the point on Earth's surface diametrically opposite to it. A pair of points antipodal (ænˈtɪpədəl) to each other are situated such that a straight line connecting the two would pass through Earth's center. Antipodal points are as far away from each other as possible. The North and South Poles are antipodes of each other. In the Northern Hemisphere, "the Antipodes" may refer to Australia and New Zealand, and Antipodeans to their inhabitants.
Orogeny is a mountain building process that takes place at a convergent plate margin when plate motion compresses the margin. An orogenic belt or orogen develops as the compressed plate crumples and is uplifted to form one or more mountain ranges. This involves a series of geological processes collectively called orogenesis. These include both structural deformation of existing continental crust and the creation of new continental crust through volcanism.
