Water, Water Everywhere

1768 1768
40.00W20.00N
NAT

MID-ATLANTIC
	Since we live on land and usually only look at the ocean from the seashore, it is easy to forget what a huge part of our world is actually covered with water.
	The volume of water in the world is 14 times greater than the volume of land above sea level. Seven-tenths of the earth is covered by water. If the earth's surface was exactly level, our planet would be entirely covered with two miles of water.
	Not only are the oceans important for their size, but they are also the main source for the water that evaporates to become clouds and water the earth. In addition, they are the great transportation ways of international trade; the fish and plants of the sea are a major source of food; and sea plants provide much of the oxygen in our atmosphere.
	The biggest of the world's three main oceans is the Pacific. It is almost as large as the Atlantic and Indian oceans combined. Ferdinand Magellan named the Pacific after crossing the rough Atlantic. He thought it was much more peaceful, or "pacific."
	The Atlantic, the second largest ocean, was named after Atlantis, a legendary country supposedly located there. The Greek philosopher Plato said Atlantis sank beneath the ocean.
	The Indian Ocean is named after the subcontinent of India, which juts far out into the ocean.
	The first attempt to systematically study the ocean was undertaken in 1768 by Captain James Cook. Cook took an astronomer and biologist on his explorations of the South Pacific.
	In 1872 the British surveying ship Challenger embarked on a three-year voyage of 69,000 miles. The report from the journey filled 50 volumes and added more to man's knowledge of the sea than all that had been learned before.
	Though scientists have found life even at great depths, most sea life is near the surface, especially along the continental shelves. These shelves are wide, gently sloping areas next to the continents. At the edge of the shelf, the water suddenly increases in depth, dropping two or three miles in depth to another flat area, often called the Plain of the Abyss. Only in a few trenches in the ocean floor is the water deeper than this plain.
	The ocean's water is constantly in motion. There are actually rivers of water flowing through the oceans that are much larger than any rivers on land. The biggest of these is the Gulf Stream, which flows out of the Gulf of Mexico, north along the East Coast of the United States, then divides to warm Iceland and the west coast of Europe. The Gulf Stream is 90 miles wide and a half mile deep.
	The ocean is also moved by the moon and sun. Their gravity causes the water to rise and fall in certain spots. Because the moon is much closer to the earth, the tides it causes are much higher.
