Steve McKenzie, age 10, of Camden, N.J., for his question:
WHICH OCEAN IS THE WORLD'S LARGEST?
The largest and deepest ocean in the world is the Pacific
Ocean. It is so large that it covers over a third of the earth's entire surface and it contains more than half of its free water. Sometimes the Pacific is divided into nominal sections with the part north of the equator called the North Pacific and that part south of the equator, the South Pacific.
The great Portuguese navigator Ferdinand Magellan gave the great ocean its name in 1520. Pacific means peaceful, because this was the first impression Magellan received when he first saw the ocean.
The Pacific ocean contains more than 30,000 islands, which have a total land area that amounts to only one quarter of one percent of the ocean's surface area.
Largest islands in the western region, which rise from the broad continental shelf and are geologically continental in character, include Japan, Taiwan, the Philippines, Indonesia, New Guinea and New Zealand.
Along the eastern edge of the Pacific the continental shelf is narrow and steep, with few island areas. The major groups are the Galapagos at the equator, which rise from the Chile Plate, and the Aleutians in th.e north, which are part of the North American continental shelf.
The oceanic islands, collectively called Oceania, are the tops of mountains or mountain chains built up from the ocean basin by extruding molten rock. The mountains that remain submerged are called seamounts. In may areas, particularly the South Pacific, the land features above the sea surface are accretions of shell material.
The Pacific is the oldest of the existing oceans basins, its oldest rocks having been dated at about 200 million years.
The major features of the basin and rim have been shaped by the phenomena associated with plate tectonics. The driving forces for Pacific ocean currents are the earths rotation, wind friction at the surface of the waters and variations in seawater densities due to differences in temperature and saltiness.
The surface currents of the North Pacific consist of two gyres, or circular systems. In the extreme north the counterclockwise Subarctic Gyre encompasses the westward flowing Alaska Current and the eastward flowing Subarctic Current.
The main body of the North Pacific, however, is dominated by the huge North Central Gyre, which circulates clockwise. It encompasses the North Pacific Current, flowing east, the
California Current, flowing west, and the Kuroshio (or Japan) Current, flowing north up the coast of Japan.
Close to the equator, the eastward flowing Equatorial Countercurrent separates the North and South Pacific systems but sends most of its waters into the North Equatorial Current.
The South Pacific is dominated by the counterclockwise moving South Central Gyre.