Pacific Ocean: Map

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The Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Tepre Pacificum, "peaceful sea", bestowed upon it by the Portuguesemarker explorer Ferdinand Magellan. It extends from the Arctic in the north to Antarcticamarker in the south, bounded by Asia and Australiamarker in the west, and the Americas in the east. At169.2 million square kilometres (65.3 million square miles) in area, this largest division of the World Ocean – and, in turn, the hydrosphere – covers about 46% of the Earth's water surface and about 30% of its total surface. The equator subdivides it into the North Pacific Ocean and South Pacific Ocean, with two exceptions: the Galápagosmarker and Gilbert Islands, while straddling the equator, are deemed wholly within the South Pacific. The Mariana Trenchmarker in the western North Pacific is the deepest point in the Pacific and in the world, reaching a depth of .
The Pacific Ocean.


Overview



The 'Pacific ocean' encompasses aproximately a third of the Earth's surface, having an area of 179.7 million square kilometres (69.4 million sq mi and 161 million cubic mi) —significantly larger than Earth's entire landmass, with room for another Africa to spare. Extending approximately 15,500 kilometres (9,600  mi) from the Bering Seamarker in the Arctic to the icy margins of Antarcticamarker's Ross Seamarker in the south (although the Antarctic regions of the Pacific are sometimes described as part of the circumpolar Southern Oceanmarker), the Pacific reaches its greatest east-west width at about 5°N latitude, where it stretches approximately 19,800 kilometres (12,300 mi) from Indonesiamarker to the coast of Colombiamarker and Perumarker – halfway across the world, and more than five times the diameter of the Moon. The western limit of the ocean is often placed at the Strait of Malaccamarker. The lowest known point on earth—the Mariana Trenchmarker—lies 10,911 metres (35,797 ft) below sea level. Its average depth is 4,280 metres (14,000 ft).

The Pacific contains about 25,000 islands (more than the total number in the rest of the world's oceans combined), the majority of which are found south of the equator. Including partially submerged islands, the figure is substantially higher.

The Pacific Ocean is currently shrinking from plate tectonics, while the Atlantic Oceanmarker is increasing in size, by roughly an inch per year (2–3 cm/yr) on 3 sides, roughly averaging 0.2 square miles (0.5 km2) a year.


Along the Pacific Ocean's irregular western margins lie many seas, the largest of which are the Celebes Seamarker, Coral Seamarker, East China Seamarker, Philippine Seamarker, Sea of Japanmarker, South China Seamarker, Sulu Seamarker, Tasman Seamarker, and Yellow Seamarker. The Strait of Malaccamarker joins the Pacific and the Indian Oceansmarker on the west, and Drake Passagemarker and the Straits of Magellanmarker link the Pacific with the Atlantic Oceanmarker on the east. To the north, the Bering Straitmarker connects the Pacific with the Arctic Oceanmarker.

As the Pacific straddles the ± 180° meridian, the West Pacific (or western Pacific, near Asia) is in the Eastern Hemisphere, while the East Pacific (or eastern Pacific, near the Americas) is in the Western Hemispheremarker.

For most of Magellan's voyage from the Strait of Magellanmarker to the Philippinesmarker, the explorer indeed found the ocean peaceful. However, the Pacific is not always peaceful. Many tropical storms batter the islands of the Pacific. The lands around the Pacific rim are full of volcanoes and often affected by earthquakes. Tsunamis, caused by underwater earthquakes, have devastated many islands and destroyed entire towns.

Water characteristics

Water temperatures in the Pacific vary from freezing in the poleward areas to about near the equator. Salinity also varies latitudinally. The water near the equator is less salty than that found in the mid-latitudes because of abundant equatorial precipitation throughout the year. Poleward of the temperate latitudes salinity is also low, because little evaporation of seawater takes place in these frigid areas.

The motion of Pacific waters is generally clockwise in the Northern Hemispheremarker (the North Pacific gyre) and counter-clockwise in the Southern Hemispheremarker. The North Equatorial Current, driven westward along latitude 15°N by the trade winds, turns north near the Philippines to become the warm Japan or Kuroshio Current.

Turning eastward at about 45°N, the Kuroshio forks and some waters move northward as the Aleutian Current, while the rest turn southward to rejoin the North Equatorial Current. The Aleutian Current branches as it approaches North America and forms the base of a counter-clockwise circulation in the Bering Sea. Its southern arm becomes the chilled slow, south-flowing California Current.

The South Equatorial Current, flowing west along the equator, swings southward east of New Guineamarker, turns east at about 50°S, and joins the main westerly circulation of the Southern Pacific, which includes the Earth-circling Antarctic Circumpolar Current. As it approaches the Chileanmarker coast, the South Equatorial Current divides; one branch flows around Cape Hornmarker and the other turns north to form the Peru or Humboldt Current.

Geology

The andesite line is the most significant regional distinction in the Pacific. It separates the deeper, mafic igneous rock of the Central Pacific Basin from the partially submerged continental areas of felsic igneous rock on its margins. The andesite line follows the western edge of the islands off Californiamarker and passes south of the Aleutian arcmarker, along the eastern edge of the Kamchatka Peninsulamarker, the Kuril Islandsmarker, Japanmarker, the Mariana Islandsmarker, the Solomon Islandsmarker, and New Zealandmarker's North Islandmarker. The dissimilarity continues northeastward along the western edge of the Andes Cordillera along South America to Mexicomarker, returning then to the islands off California. Indonesiamarker, the Philippines, Japan, New Guinea, and New Zealand—all eastward extensions of the continental blocks of Asia, Australia and Zealandia—lie outside the Andesite Line.

The pacific ocean takes up roughly one third of the earth's surface, having an area of 179.7 million square kilometres. The Pacific contains about 25,000 islands (more than the total number in the rest of the world's oceans combined), the majority of which are found south of the equator, Including partially submerged islands. The pacific ocean was mapped by a man named Abraham Ortelius, he called it Maris Pacifici because if you name it more accurately it is named the Descriptio Maris Pacifici which is interpreted as; Description of the Pacific Sea. The pacific ocean has several long seamount chains (which are chains of mountains submerging from the ocean seafloor) formed by hotspot volcanism. “the ring of fire” is the worlds largest belt of explosive volcanism. The Ring of Fire is named after the several hundred active volcanoes that sit above the various subduction zones(which is a geological process in which one edge of a crustal plate is forced sideways and downward into the mantle below another plate).

Within the closed loop of the Andesite Line are most of the deep troughs, submerged volcanic mountains, and oceanic volcanic islands that characterize the Pacific basin. Here basaltic lavas gently flow out of rifts to build huge dome-shaped volcanic mountains whose eroded summits form island arcs, chains, and clusters. Outside the Andesite Line, volcanism is of the explosive type, and the Pacific Ring of Fire is the world's foremost belt of explosive volcanism. The Ring of Fire is named after the several hundred active volcanoes that sit above the various subduction zones.

The Pacific Ocean is the only ocean which is almost totally bounded by subduction zones. Only the Antarctic and Australian coasts have no nearby subduction zones.

Seamount chains

The Pacific Ocean contains several long seamount chains, formed by hotspot volcanism. These include the Emperor Seamountsmarker chain, the Louisville seamount chain, and the Hawaiian Islands.

Landmasses

Right
The largest landmass entirely within the Pacific Ocean is the island of New Guineamarker— the second largest island in the world. Almost all of the smaller islands of the Pacific lie between 30°N and 30°S, extending from Southeast Asia to Easter Islandmarker; the rest of the Pacific Basin is almost entirely submerged. During the Last glacial period, New Guinea was part of Australia so the largest landmass would have been BorneomarkerPalawanmarker.

The great triangle of Polynesia, connecting Hawaiimarker, Easter Islandmarker, and New Zealandmarker, encompasses the island arcs and clusters of the Cook Islandsmarker, Marquesas Islandsmarker, Samoamarker, Societymarker, Tokelaumarker, Tongamarker, Tuamotumarker, Tuvalumarker and the Wallis and Futunamarker islands.

North of the equator and west of the International Date Linemarker are the numerous small islands of Micronesia, including the Caroline Islandsmarker, the Marshall Islandsmarker and the Mariana Islandsmarker.
In the southwestern corner of the Pacific lie the islands of Melanesia, dominated by New Guinea. Other important island groups of Melanesia include the Bismarck Archipelagomarker, Fijimarker, New Caledoniamarker, the Solomon Islandsmarker and Vanuatumarker.

Islands in the Pacific Ocean are of four basic types: continental islands, high islands, coral reefs, and uplifted coral platforms. Continental islands lie outside the Andesite line and include New Guinea, the islands of New Zealand, and the Philippinesmarker. These islands are structurally associated with nearby continents. High islands are of volcanic origin, and many contain active volcanoes. Among these are Bougainvillemarker, Hawaii, and the Solomon Islands.

The third and fourth types of islands are both the result of coralline island building. Coral reefs are low-lying structures that have built up on basaltic lava flows under the ocean's surface. One of the most dramatic is the Great Barrier Reefmarker off northeastern Australia. A second island type formed of coral is the uplifted coral platform, which is usually slightly larger than the low coral islands. Examples include Banabamarker (formerly Ocean Island) and Makateamarker in the Tuamotu group of French Polynesiamarker.

History and economy



Important human migrations occurred in the Pacific in prehistoric times, most notably those of the Polynesians from the Asian edge of the ocean to Tahitimarker and then to Hawaiimarker, New Zealandmarker, and Easter Islandmarker.

The ocean was sighted by Europeans early in the 16th century, first by the Spanish explorer Vasco Núñez de Balboa who crossed the Isthmus of Panama in 1513, and then by the Portuguese explorer Ferdinand Magellan, who sailed the Pacific during his circumnavigation from 1519 to 1522. In 1564, conquistadors crossed the ocean from Mexico led by Miguel López de Legazpi who sailed to the Philippinesmarker and Mariana Islandsmarker. For the remainder of the 16th century, Spanish influence was paramount, with ships sailing from Spainmarker to the Philippines, New Guineamarker, and the Solomon Islandsmarker.

During the 17th century, the Dutch, sailing around southern Africa, dominated discovery and trade; Abel Janszoon Tasman discovered Tasmaniamarker and New Zealandmarker in 1642. The 18th century marked a burst of exploration by the Russians in Alaskamarker and the Aleutian Islandsmarker, the French in Polynesia, and the British in the three voyages of James Cook to the South Pacific and Australia, Hawaiimarker, and the North American Pacific Northwest.

Growing imperialism during the 19th century resulted in the occupation of much of Oceania by European powers, and later, the United Statesmarker and Japanmarker. Significant contributions to oceanographic knowledge were made by the voyages of HMS Beagle in the 1830s, with Charles Darwin aboard; HMS Challenger during the 1870s; the USS Tuscarora (1873–76); and the German Gazelle (1874–76). Although the United States gained control of the Philippinesmarker from Spainmarker in 1898, Japan controlled most of the western Pacific by 1914 and occupied many other islands during World War II. However, by the end of that war, Japan was defeated and the U.S. Pacific Fleet was the virtual master of the ocean. Since the end of World War II, many former colonies in the Pacific have become independent state.

The exploitation of the Pacific's mineral wealth is hampered by the ocean's great depths. In shallow waters of the continental shelves off the coasts of Australia and New Zealand, petroleum and natural gas are extracted, and pearls are harvested along the coasts of Australia, Japanmarker, Papua New Guineamarker, Nicaraguamarker, Panamamarker, and the Philippinesmarker, although in sharply declining volume in some cases. The Pacific's greatest asset is its fish. The shoreline waters of the continents and the more temperate islands yield herring, salmon, sardines, snapper, swordfish, and tuna, as well as shellfish.

Environmental issues



Marine pollution is a generic term for the harmful entry into the ocean of chemicals or particles. The biggest culprits are people who use the rivers for disposing of their waste. The rivers then empty into the Ocean, and with it the many chemicals used as fertilizers in agriculture. The excess of oxygen depleting chemicals in the water leads to hypoxia and the creation of a dead zone.

Marine debris, also known as marine litter, is a term used to describe human-created waste that has found itself floating in a lake, sea, ocean or waterway. Oceanic debris tends to accumulate at the centre of gyres and coastlines, frequently washing aground where it is known as beach litter.

Bordering countries and territories





Major ports and harbours





See also



References





Further reading

Based on public domain text from US Naval Oceanographer


External links




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