Pacific Ocean



The Pacific Ocean (from the name Mare Pacificum, "peaceful sea", bestowed upon it by the  explorer ) is the largest of the 's ic divisions. It extends from the in the north to the  in the south, bounded by  and  on the west and the  on the east. At 169.2 million s (65.3 million square miles) in area, this largest division of the – and, in turn, the  – covers about 46% of the Earth's water surface and about 32% of its total surface area, making it larger than all of the Earth's land area combined. The subdivides it into the North Pacific Ocean and South Pacific Ocean. The in the western North Pacific is the deepest point in the Pacific and the world, reaching a depth of 10,911 metres (35,798 ft)

Overview
The ocean encompasses a third of the 's surface, having an area of 179.7 million square kilometres (69.4 million sq mi and 161 million cubic mi) &mdash;significantly larger than Earth's entire landmass, with room for another to spare. Extending approximately 15,500 kilometres (9,600 mi) from the  in the  to the icy margins of 's  in the south (although the Antarctic regions of the Pacific are sometimes described as part of the circumpolar ), the Pacific reaches its greatest east-west width at about 5°N latitude, where it stretches approximately 19,800 kilometres (12,300 mi) from  to the coast of  and  - halfway across the world. The western limit of the ocean is often placed at the. The lowest point on earth&mdash;the &mdash;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 (more than the total number in the rest of the world's oceans combined), the majority of which are found south of the.

The Pacific Ocean is currently shrinking from, while the is increasing in size.

Along the Pacific Ocean's irregular western margins lie many seas, the largest of which are the, , , , , , , , and. The joins the Pacific and the s on the west, and the  links the Pacific with the Atlantic Ocean on the east. To the north, the connects the Pacific with the.

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



For most of Magellan's voyage from the Strait of Magellan to the, the explorer indeed found the ocean peaceful. However, the Pacific is not always peaceful. Many s (s, the equivalent of Atlantic s), batter the islands of the Pacific. The lands around the Pacific rim are full of es and often affected by s. s, 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 25-30 °C 84 °F  near the equator. 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 Pacific Ocean is generally warmer than the Atlantic ocean.

The surface circulation of Pacific waters is generally clockwise in the (the ) and counter-clockwise in the. The, driven westward along latitude 15°N by the s, turns north near the Philippines to become the warm Japan or.

Turning eastward at about 45°N, the Kuroshio forks and some waters move northward as the, 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, flowing west along the equator, swings southward east of , turns east at about 50°S, and joins the main westerly circulation of the Southern Pacific, which includes the Earth-circling. As it approaches the an coast, the South Equatorial Current divides; one branch flows around and the other turns north to form the Peru or.

Geology
The is the most significant regional distinction in the Pacific. It separates the deeper,  of the Central Pacific Basin from the partially submerged continental areas of  igneous rock on its margins. The andesite line follows the western edge of the islands off and passes south of the, along the eastern edge of the , the , , the , the , and. The dissimilarity continues northeastward along the western edge of the Cordillera along  to, returning then to the islands off California. , the Philippines, Japan, New Guinea, and New Zealand&mdash;all eastward extensions of the continental blocks of and &mdash;lie outside the Andesite Line.

Within the closed loop of the andesite line are most of the deep troughs, submerged volcanic mountains, and oceanic volcanic islands that characterize the. 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 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 boundary with the Antarctic plate is not a subduction zone.

Landmasses
The largest landmass entirely within the Pacific Ocean is the of &mdash; 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 to ; the rest of the Pacific Basin is almost entirely submerged.

The great triangle of, connecting , , and , encompasses the island arcs and clusters of the , , , , , , , &  islands.

North of the equator and west of the International Date Line are the numerous small islands of, including the , the and the.

In the southwestern corner of the Pacific lie the islands of, dominated by New Guinea. Other important island groups of Melanesia include the, , , the and.

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 and include New Guinea, the islands of New Zealand, and the. These islands are structurally associated with nearby continents. High islands are of volcanic origin, and many contain active volcanoes. Among these are, Hawaii, & 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 off northeastern. A second island type formed of coral is the uplifted coral platform, which is usually slightly larger than the low coral islands. Examples include (formerly Ocean Island) and  in the Tuamotu group of.

History and economy
Important migrations occurred in the Pacific in prehistoric times, most notably those of the  (specifically, the ), from the Asian edge of the ocean to  and then to Hawaii, New Zealand, and Easter Island.

The ocean was sighted by Europeans early in the 16th century, first by the explorer  (1513), who crossed the Isthmus of Panama, and then by Ferdinand Magellan, who sailed the Pacific during his circumnavigation (1519-1522). In 1564, s crossed the ocean from Mexico led by who sailed to the  and Mariana Islands. For the remainder of the 16th century, influence was paramount, with ships sailing from Spain to the Philippines, New Guinea, and the Solomon Islands; the s linked  and. In 16th century also Ragusan galleys from led by Vice Bune explored southwestern Pacific, and discovered the islands of,  (New Hebrides), etc.

During the 17th century, the, sailing around southern Africa, dominated discovery and trade; discovered  and New Zealand in 1642; in that century Ragusan traders prevailed in Melanesia. The 18th century marked a burst of exploration by the ns in and the Aleutian Islands, the  in Polynesia, and the British in the three voyages of  (to the South Pacific and Australia, Hawaii, and the n ).

Growing during the 19th century resulted in the occupation of much of Oceania by Great Britain and France, followed by the. Significant contributions to oceanographic knowledge were made by the voyages of in the 1830s, with  aboard;  during the 1870s; the USS Tuscarora (1873-76); and the German Gazelle (1874-76). Although the United States conquered the Philippines in 1898, Japan controlled the western Pacific by 1914 and occupied many other islands during. By the end of the war, the was the virtual master of the ocean.

Seventeen independent states are located in the Pacific: Australia,, Japan, Kiribati, Marshall Islands, Micronesia, , New Zealand, , Papua New Guinea, the Philippines, Samoa, Solomon Islands, , Tonga, Tuvalu, and. Eleven of these nations have achieved full independence since 1960. The Northern Mariana Islands are self-governing with external affairs handled by the United States, and and  are in similar relationships with New Zealand. Also within the Pacific is the U.S. state of Hawaii and several island territories and possessions of Australia, Chile,, France, Japan, New Zealand, the , and the United States.

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, Japan, Papua New Guinea,, , and the Philippines, 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, , s, , , and , as well as.

In 1986, the member nations of the declared the area a nuclear-free zone in an effort to halt  and prevent the dumping of  there.

Environmental Issues
Marine pollution is a generic term for the harmful entry into the ocean of chemicals or particles. The biggest culprit are rivers that empty into the Ocean, and with it the many chemicals used as in agriculture as well as waste from  and. The excess of oxygen depleting chemicals in the water leads to and the creation of a.

Major ports and harbours

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