Boundaries between the continentsDetermining 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.
Afro-EurasiaAfro-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.
Australia (continent)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.
Wilson CycleThe 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.
Inland seaAn 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.
AntipodesIn 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.
OrogenyOrogeny 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.
Basement (geology)In geology, basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment. The basement rocks lie below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin. In the same way, the sediments or sedimentary rocks on top of the basement can be called a "cover" or "sedimentary cover".
RegionIn geography, regions, otherwise referred to as areas, zones, lands or territories, are portions of the Earth's surface that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and the interaction of humanity and the environment (environmental geography). Geographic regions and sub-regions are mostly described by their imprecisely defined, and sometimes transitory boundaries, except in human geography, where jurisdiction areas such as national borders are defined in law.
Continental EuropeContinental Europe or mainland Europe is the contiguous mainland of Europe, excluding its surrounding islands. It can also be referred to ambiguously as the European continent, – which can conversely mean the whole of Europe – and, by some, simply as the Continent. When Eurasia is regarded as a single continent, Europe is treated as a subcontinent, and called the European subcontinent.
SubregionA subregion is a part of a larger region or continent and is usually based on location. Cardinal directions, such as south are commonly used to define a subregion. United Nations geoscheme The Statistics Division of the United Nations (UN) is in charge of the collection, processing, and dissemination of statistical information for the UN. In 1999, it developed a system of macro-geographical (continental) regions, subregions, and other selected economic groups to report advances towards achieving numerous millennial development goals worldwide.
Land bridgeIn biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea levels fall, exposing shallow, previously submerged sections of continental shelf; or when new land is created by plate tectonics; or occasionally when the sea floor rises due to post-glacial rebound after an ice age.
Shield (geology)A shield is a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. These rocks are older than 570 million years and sometimes date back to around 2 to 3.5 billion years. They have been little affected by tectonic events following the end of the Precambrian, and are relatively flat regions where mountain building, faulting, and other tectonic processes are minor, compared with the activity at their margins and between tectonic plates.
Continental driftContinental drift is the hypothesis that the Earth's continents have moved over geologic time relative to each other, thus appearing to have "drifted" across the ocean bed. The idea of continental drift has been subsumed into the science of plate tectonics, which studies the movement of the continents as they ride on plates of the Earth's lithosphere. The speculation that continents might have "drifted" was first put forward by Abraham Ortelius in 1596. A pioneer of the modern view of mobilism was the Austrian geologist Otto Ampferer.
IslandAn island or isle is a piece of subcontinental land completely surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. Sedimentary islands in the Ganges Delta are called chars. A grouping of geographically or geologically related islands, such as the Philippines, is referred to as an archipelago.
Oceanic basinIn hydrology, an 'oceanic basin (or ocean basin') is anywhere on Earth that is covered by seawater. Geologically, most of the ocean basins are large geologic basins that are below sea level. Most commonly the ocean is divided into basins following the continents distribution: the North and South Atlantic (together approximately 75 million km2/ 29 million mi2), North and South Pacific (together approximately 155 million km2/ 59 million mi2), Indian Ocean (68 million km2/ 26 million mi2) and Arctic Ocean (14 million km2/ 5.
MainlandMainland is defined as "relating to or forming the main part of a country or continent, not including the islands around it [regardless of status under territorial jurisdiction by an entity]." The term is often politically, economically and/or demographically more significant than politically associated remote territories, such as exclaves or oceanic islands situated outside the continental shelf. In geography, "mainland" can denote the continental (i.e. non-insular) part of any polity or the main island within an island nation.
EurasiaEurasia (jʊəˈreɪʒə, alsoUK-S@) is the largest continental area on Earth, comprising all of Europe and Asia. According to some geographers, physiographically, Eurasia is a single continent. The concepts of Europe and Asia as distinct continents date back to antiquity, but their borders are arbitrary and have historically been subject to change. Eurasia is connected to Africa at the Suez Canal, and the two are sometimes combined to describe the largest contiguous landmass on Earth, Afro-Eurasia.
EcoregionAn ecoregion (ecological region) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural communities and species. The biodiversity of flora, fauna and ecosystems that characterise an ecoregion tends to be distinct from that of other ecoregions.
Island countryAn island country, island state, or island nation is a country whose primary territory consists of one or more islands or parts of islands. Approximately 25% of all independent countries are island countries. Island countries are historically more stable than many continental states but are vulnerable to conquest by naval superpowers. There are great variations between island country economies: they may rely mainly on extractive industries, such as mining, fishing and agriculture, and/or on services such as transit hubs, tourism, and financial services.
