By - - USGS WATER SCIENCE FOR SCHOOLS
Added: Tue, 15 May 2012 09:10:45 UTC

We have linked to the USGS Water Science for Schools website for this story, even though it is written for a young readership, because it contains links to a lot of interesting background information. However, the story has also been featured in Discover Magazine.

Picture of Earth showing if all Earth's water (liquid, ice, freshwater, saline) was put into a sphere it would be about 860 miles (about 1,385 kilometers) in diameter. Diameter would be about the distance from Salt Lake City, Utah to Topeka, Kansas, USA. Credit: Illustration by Jack Cook, Woods Hole Oceanographic Institution (©); Howard Perlman, USGS.

As you know, the Earth is a watery place. But just how much water exists on, in, and above our planet? The picture to the left shows the size of a sphere that would contain all of Earth's water in comparison to the size of the Earth. You're probably thinking I missed a decimal point when running my calculator since surely all the water on, in, and above the Earth would fill a ball a lot larger than that "tiny" blue sphere sitting on the United States, reaching from about Salt Lake City, Utah to Topeka, Kansas. But, no, this diagram is indeed correct.

About 70 percent of the Earth's surface is water-covered, and the oceans hold about 96.5 percent of all Earth's water. But water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in you and your dog. Still, all that water would fit into that "tiny" ball. The ball is actually much larger than it looks like on your computer monitor or printed page because we're talking about volume, a 3-dimensional shape, but trying to show it on a flat, 2-dimensional screen or piece of paper. That tiny water bubble has a diameter of about 860 miles, meaning the height (towards your vision) would be 860 miles high, too! That is a lot of water.

But, as far as people are concerned, almost all of Earth's water is not usable in everyday life. Water on, in, and above the Earth is never sitting still, and thanks to the water cycle our planet's water supply is constantly moving from one place to another and from one form to another. Things would get pretty stale without the water cycle!

Read on

TAGGED: EARTH SCIENCES, SCIENCE