Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south and is bounded by the continents of Asia and Australia in the west and the Americas in the east.
At 165,250,000 square kilometers (63,800,000 square miles) in area (as defined with a southern Antarctic border), this largest division of the World Ocean—and, in turn, the hydrosphere—covers about 46% of Earth's water surface and about 32% of its total surface area, larger than all of Earth's land area combined (148,000,000 km2 [57,000,000 sq mi]).[1] The centers of both the Water Hemisphere and the Western Hemisphere are in the Pacific Ocean. Ocean circulation (caused by the Coriolis effect) subdivides it[citation needed] into two largely independent volumes of water, which meet at the equator: the North(ern) Pacific Ocean and South(ern) Pacific Ocean. The Galápagos and Gilbert Islands, while straddling the equator, are deemed wholly within the South Pacific.[2]
Its mean depth is 4,000 meters (13,000 feet).[3] Challenger Deep in the Mariana Trench, located in the western north Pacific, is the deepest point in the world, reaching a depth of 10,928 meters (35,853 feet).[4] The Pacific also contains the deepest point in the Southern Hemisphere, the Horizon Deep in the Tonga Trench, at 10,823 meters (35,509 feet).[5] The third deepest point on Earth, the Sirena Deep, is also located in the Mariana Trench.
The western Pacific has many major marginal seas, including but not limited to the South China Sea, the East China Sea, the Sea of Japan, the Sea of Okhotsk, the Philippine Sea, the Coral Sea, Java Sea and the Tasman Sea.
Though the peoples of Asia and Oceania have traveled the Pacific Ocean since prehistoric times, the eastern Pacific was first sighted by Europeans in the early 16th century when Spanish explorer Vasco Núñez de Balboa crossed the Isthmus of Panama in 1513 and discovered the great "Southern Sea" which he named Mar del Sur (in Spanish). The ocean's current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favorable winds on reaching the ocean. He called it Mar Pacífico, which in both Portuguese and Spanish means "peaceful sea".[6]
Across the continents of Asia, Australia and the Americas, more than 25,000 islands, large and small, rise above the surface of the Pacific Ocean. Multiple islands were the shells of erstwhile active volcanoes, that have laid dormant for thousands of years. Close to the equator through vast areas of blue ocean are a dot of atolls that have over intervals of time been formed by seamounts as a result of tiny coral islands strung in a ring within surroundings of a central lagoon.
