H073
If you gathered all of Earth's water into one ball, how big would it be?
Oceans cover about 71% of Earth's surface and are miles deep in places. It feels like Earth is mostly water.
Earth's water, drawn to scale
Each ball holds that water, sized against Earth and the Moon
Earth's water is a thin film spread across a huge rocky ball. The oceans look vast because they are wide, but they average only about 2.3 miles deep on a planet almost 8,000 miles across. Rolled into one ball, all of it would be about 860 miles across, smaller than the Moon. The fresh water in lakes and rivers that most people actually use would make a ball only about 35 miles across.
Things that cover a lot of area can hold surprisingly little volume. Before judging how much of something there is, ask how deep it goes, not just how far it spreads.
Try it somewhere else
A city's new solar farm covers more ground than its downtown.
Does that tell you how much of the city's power it can supply?
Where the fresh water hides
About 97% of Earth's water is salty ocean. Most of the remaining fresh water is locked in ice caps and glaciers or underground. Lakes and rivers hold only a tiny fraction of a percent of all the water on the planet, which is why the smallest ball in the picture is so small.
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Sources: U.S. Geological Survey, "How Much Water Is There on Earth?" (Water Science School; illustration by Howard Perlman and Jack Cook). Earth and Moon diameters: NASA.