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<h1>Continents</h1>
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<h3>Definitions</h3>
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<td><p>By convention, "continents are understood to be large, continuous, discrete masses of land, ideally separated by expanses of water." Many of the seven most commonly recognized continents identified by convention are not discrete landmasses separated by water. The criterion "large" leads to arbitrary classification: Greenland, with a surface area of 2,166,086 square kilometres (836,330 sq mi) is considered the world's largest island, while Australia, at 7,617,930 square kilometres (2,941,300 sq mi) is deemed a continent. Likewise, the ideal criterion that each be a continuous landmass is often disregarded by the inclusion of the continental shelf and oceanic islands, and contradicted by classifying North and South America as two continents; and/or Eurasia and Africa as two continents, with no natural separation by water. This anomaly reaches its extreme if the continuous land mass of Europe and Asia is considered to constitute two continents. The Earth's major landmasses are washed upon by a single, continuous world ocean, which is divided into a number of principal oceanic components by the continents and various geographic criteria. Continents are sometimes extended beyond the major landmasses, in a way that every bit of land on earth is included in a continent.</td>
<td><p><img src="Dymaxion_map.png" alt="Dymaxion map" title="Dymaxion map"/>
<h5>A Dymaxion map shows land masses with minimal shape distortion</h5>
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<h2>Extent of continents</h2>
<p>The narrowest 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. In this sense the term continental Europe (sometimes "the Continent") is used to refer to mainland Europe, excluding islands such as Great Britain, Ireland, Malta and Iceland, and the term continent of Australia may refer to the mainland of Australia, excluding Tasmania and New Guinea. Similarly, the continental United States refers to the 48 contiguous states in central North America and may include Alaska in the northwest of the continent (the two being separated by Canada), while excluding Hawaii in the middle of the Pacific Ocean.</p>
<p>From 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. From this perspective the edge of the continental shelf is the true edge of the continent, as shorelines vary with changes in sea level. 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.</p>
<p>As a cultural construct, the concept of a continent may go beyond the continental shelf to include oceanic islands and continental fragments. In this way, Iceland is considered part of Europe and Madagascar part of Africa. Extrapolating the concept to its extreme, some geographers group the Australasian continental plate with other islands in the Pacific into one continent called Oceania. This divides the entire land surface of the Earth into continents or quasi-continents.</p>
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<h2>Separation of continents</h2>
<img src="Island_countries.png" alt="Island countries" title="Island countries"/>
<h4>Map of island countries: these states are often grouped geographically with a neighboring continental landmass</h4>
<p>The ideal criterion that each continent be a discrete landmass is commonly disregarded due to historical conventions. Of the seven most commonly recognized continents, only Antarctica and Australia are completely separated from other continents.</p>
<p>Several continents are defined not as absolutely distinct bodies but as "more or less discrete masses of land". Asia and Africa are joined by the Isthmus of Suez, and North and South America by the Isthmus of Panama. Both these isthmuses are very narrow compared to the bulk of the landmasses they join, and both are transected by artificial canals (the Suez and Panama canals), which provide maritime passage across these landmasses.</p>
<p>The traditional division of the landmass of Eurasia into the continents of Asia and Europe is an anomaly, as no sea separates them. The alternative view—in geology and geography—that Eurasia is a single continent results in a six-continent view of the world. Some view separation of Eurasia into Europe and Asia as a residue of Eurocentrism: "In physical, cultural and historical diversity, China and India are comparable to the entire European landmass, not to a single European country. A better (if still imperfect) analogy would compare France, not to India as a whole, but to a single Indian state, such as Uttar Pradesh." However, for historical and cultural reasons, the view of Europe as a separate continent continues in several categorizations.</p>
<p>North America and South America are treated as separate continents in the seven-continent model. However, they may also be viewed as a single continent known as America or the Americas. This viewpoint was common in the United States until World War II, and remains prevalent in some Asian six-continent models. This remains the more common vision in Latin American countries, Spain, Portugal, France, Italy and Greece, where they are taught as a single continent.</p>
<p>When continents are defined as discrete landmasses, embracing all the contiguous land of a body, then Asia, Europe and Africa form a single continent known by various names such as Afro-Eurasia. This produces a four-continent model consisting of Afro-Eurasia, America, Antarctica and Australia.</p>
<p>When sea levels were lower during the Pleistocene ice age, greater areas of continental shelf were exposed as dry land, forming land bridges. At this time Australia-New Guinea was a single, continuous continent. Likewise the Americas and Afro-Eurasia were joined by the Bering land bridge. Other islands such as Great Britain were joined to the mainlands of their continents. At that time there were just three discrete continents: Afro-Eurasia-America, Antarctica, and Australia-New Guinea.</p>
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<td><p><a href="http://www.nationalgeographic.com/" target="_blank">National Geographic</a></td>
<td><p><a href="http://www.canadiangeographic.ca/" target="_blank">Canadian Geographic</a></td>
<td><p><a href="http://www.theweathernetwork.com/" target="_blank">The Weather Network</a></td>
<td><p><a href="http://en.wikipedia.org/wiki/Continent" target="_blank">Continents on Wikipedia</a></td>
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<p>Created and designed by Radu Poenaru © 2015</p>
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