* The "seven seas" is a figurative term meaning all the waters of the earth. The expression first appeared in ancient literature.
* One vast ocean covers the face of the earth and it is called the "world ocean." All the so-called "oceans" on maps and globes are really only parts of the world ocean. The continents of the earth - North and South America, Europe, Asia, Africa, Antarctica, and Australia - are all but islands in this one huge body of water.
* The parts of the world ocean cut by points of land or by islands are called seas.
* The largest ocean on earth is the Pacific and is about 63,800,000 square miles in area.
* If the earth were smooth, all the land areas would be covered by seawater to a depth of some 8,810 feet - or one and two-thirds miles.
* "Sea level" of earth's oceans varies in elevation by as much as 600 feet.
* The point halfway between average high tide and average low tide is called sea level.
* Ninety percent of the earth's oceans are more than two miles deep, but the average depth of the Atlantic is 12,500 feet. A mile down, the weight of the water above that level exerts pressure of one ton per square inch, and temperatures hover between 30 and 39 degrees Fahrenheit.
* Twice every day, along most of the coasts of the world, waters of the ocean rise and fall, producing the tides. The incoming tide is called the "flood" and the outgoing, the "ebb."
* Changes in sea levels can be produced by ice ages. Extreme glaciation could drop the sea level by 300 feet, leaving many seaports high and dry. If all the polar ice melted, the seas could rise as much as 300 feet, covering Florida and other coastal areas.
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