Earth's Water Cover

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Earth&slquo;s Water Cover

At present well over 70 percent of the earth's surface is covered by water, and notable the large bodies of water are contained within specific basins. This is because of a peculiarity in the earth's evolution that resulted in there being continents and islands.

To grasp the magnitude of the earth's water cover, imagine all of the land leveled out evenly so that the earth's surface is a smooth sphere. With the waters distributed evenly over the entire world, the present supply of water would cover the entire globe to a depth of about 7,500 feet. This of course would make the earth a planet with a truly liquid surface that would appear from outer space as a blue planet with no surface markings and with widely scattered clouds.

In reality the average depth of oceanic waters at present exceeds five times the height of the land. The deepest sounding ever done, in 1962 in the Mariana Trench, just southeast of Guam, indicated that the water was almost seven miles deep.

To picture the relative depth of this area, imagine the tallest mountain in the world, Mount Everest (29,028), dropped into a trench 35,838 feet deep. It would still be covered by water to a depth of over one and a quarter miles!

As stated earlier, over two—thirds of the planet's surface is covered by water. The volume is equal to about 370 quintillion gallons. Put still another way, there is enough water to provide each human on earth with about one hundred million gallons — which is a lot of water. However, only a small and ever—decreasing fraction is available for human consumption. Use it wisely and sparingly!

From the book: 
Our Fascinating Earth