The Atlantic Ocean is the second-largest of the world's five oceanic divisions, with an area of about 85,133,000 km2 (32,870,000 sq mi). It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for separating the New World of the Americas from the Old World of Afro-Eurasia.
Atlantis is a fictional island mentioned in Plato's works Timaeus and Critias as part of an allegory on the hubris of nations. In the story, Atlantis is described as a naval empire that ruled all Western parts of the known world, making it the literary counter-image of the Achaemenid Empire. After an ill-fated attempt to conquer "Ancient Athens," Atlantis falls out of favor with the deities and submerges into the Atlantic Ocean. Since Plato describes Athens as resembling his ideal state in the Republic, the Atlantis story is meant to bear witness to the superiority of his concept of a state.
An 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.
The geography of New Caledonia (Nouvelle-Calédonie), an overseas collectivity of France located in the subregion of Melanesia, makes the continental island group unique in the southwest Pacific. Among other things, the island chain has played a role in preserving unique biological lineages from the Mesozoic. It served as a waystation in the expansion of the predecessors of the Polynesians, the Lapita culture. Under the Free French it was a vital naval base for Allied Forces during the War in the Pacific.
Seychelles is a small island country east of the African continent located in the Sea of Zanj due north of Madagascar, with Antsiranana as its nearest foreign city. Seychelles lies between approximately 4ºS and 10ºS and 46ºE and 54ºE. The nation is an archipelago of 155 tropical islands, some granite and some coral. the majority of which are small and uninhabited. The landmass is only 452 km2 (175 sq mi), but the islands are spread wide over an exclusive economic zone of 1,336,559 km2 (516,048 sq mi). About 90 percent of the population of 100,000 live on Mahé, 9 percent on Praslin and La Digue. Around a third of the land area is the island of Mahé and a further third the atoll of Aldabra.
Mu is a lost continent introduced by Augustus Le Plongeon (1825–1908), who identified the "Land of Mu" with Atlantis. The name was subsequently identified with the hypothetical land of Lemuria by James Churchward (1851–1936), who asserted that it was located in the Pacific Ocean before its destruction. The place of Mu in both pseudoscience and fantasy fiction is discussed in detail in Lost Continents by L. Sprague de Camp.
Lemuria, or Limuria, was a continent proposed in 1864 by zoologist Philip Sclater, theorized to have sunk beneath the Indian Ocean, later appropriated by occultists in supposed accounts of human origins. The theory was discredited with the discovery of plate tectonics and continental drift in the 20th century.
Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial because its bulk composition is richer in aluminium silicates (Al-Si) and has a lower density compared to the oceanic crust, called sima which is richer in magnesium silicate (Mg-Si) minerals. Changes in seismic wave velocities have shown that at a certain depth, there is a reasonably sharp contrast between the more felsic upper continental crust and the lower continental crust, which is more mafic in character.
In 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.
There are several hypotheses about real-world events that could have inspired Plato's fictional story of Atlantis, told in the Timaeus and Critias. While Plato's story was not part of the Greek mythic tradition and his dialogues use it solely as an allegory about hubris, researchers have speculated about real natural disasters that could have served as inspiration. Additionally, many works of pseudohistory and pseudoarchaeology treat the story as fact, offering reinterpretations which tie to national mysticism or theories of ancient aliens. While Plato's story explicitly locates Atlantis in the Atlantic Ocean beyond the Pillars of Hercules, location hypotheses include Helike, Thera, Troy, and the North Pole.
The Lord Howe Rise is a deep sea plateau which extends from south west of New Caledonia to the Challenger Plateau, west of New Zealand in the south west of the Pacific Ocean. To its west is the Tasman Basin and to the east is the New Caledonia Basin. Lord Howe Rise has a total area of about 1,500,000 km2 (580,000 sq mi), and generally lies about 750 to 1,200 metres under water. It is part of Zealandia, a much larger continent that is now mostly submerged, and so is composed of continental crust. Some have included the 3,500 m (11,500 ft) deep New Caledonia Basin as within the rise, given its continental crust origin, and this would give a larger total area of 1,950,000 km2 (750,000 sq mi).
Doggerland was an area of land in Northern Europe, now submerged beneath the North Sea, that connected Britain to continental Europe. It was repeatedly exposed at various times during the Pleistocene epoch due to the lowering of sea levels during glacial periods. It was last flooded by rising sea levels around 6500–6200 BCE. The flooded land is known as the Dogger Littoral. Geological surveys have suggested that it stretched from what is now the east coast of Great Britain to what is now the Netherlands, the western coast of Germany and the Danish peninsula of Jutland. It was probably a rich habitat with human habitation in the Mesolithic period, although rising sea levels gradually reduced it to low-lying islands before its final submergence, possibly following a tsunami caused by the Storegga Slide. Doggerland was named after the Dogger Bank, which in turn was named after 17th-century Dutch fishing boats called doggers.
Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin.
Zealandia, 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 Gondwana 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. A 2021 study suggests Zealandia is over a billion years old, about twice as old as geologists previously thought.
A continent is any of several large geographical regions. Continents are generally identified by convention rather than any strict criteria. A continent could be a single landmass or a part of a very large landmass, as in the case of Asia or Europe. Due to this, the number of continents varies; up to seven or as few as four geographical regions are commonly regarded as continents. Most English-speaking countries recognize seven regions as continents. In order from largest to smallest in area, these seven regions are Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Different variations with fewer continents merge some of these regions; examples of this are merging North America and South America into America, Asia and Europe into Eurasia, and Africa, Asia, and Europe into Afro-Eurasia.
Zealandia is an area of mostly submerged continental crust that contains New Zealand and New Caledonia.
