Expansion of water in the world

Expansion of water in the world

Why do you think Earth is often called the "water planet"? Perhaps an astronaut can see that there is much more water than land on Earth. Oceans cover nearly 71 percent of Earth's surface.

The chart we can shows how Earth's water is distributed. Most of Earth's water - more than 97.5 percent is salt water that is found in the oceans. Only 2.5 percent about three quarters is found in the huge masses of ice near the North and South poles. A fraction more is found in the atmosphere. Most water in the atmosphere is invisible water vapor the gaseous form of water less than a percent of the water on Earth is fresh water that is available for humans to use.

Oceans

Your journey starts in Miami, Florida. From here, you can sail completely around the world without ever going ashore. Although people have given names to regions of the ocean, these regions are all connected, forming a single world ocean.

First, you sail southeast across the Atlantic Ocean toward Africa. Swinging around the continent's southern tip, you enter the smaller but deeper Indian Ocean. After zigzagging among the islands of Indonesia, you head east across the Pacific Ocean, the longest part of your trip. This vast ocean, dotted with islands, covers an area greater than all the land on Earth put together.

Ice

How can you get back to Miami? If you're not in a hurry, you could sail all the way around South America. But watch out for icebergs! These floating chunks of ice are your first encounter with fresh water in your journey. Icebergs in the Southern Pacific and Atlantic oceans have broken off the massive sheets of ice that cover most of Antarctica. You would also find icebergs in the Arctic Ocean around the North Pole.

Rivers and Lakes

To see examples of fresh water in rivers and lakes, you'll have to make a side trip inland. Sail north past Nova Scotia, Canada, to the beginning of the St. Lawrence River. Suddenly the river widens and you enter Lake Ontario, one of North America's five Great Lakes. Together, the Great Lakes cover an area nearly twice the size of New York state. They contain nearly 20 percent of all the water in the world's freshwater lakes.

Below Earth's Surface

On your journey around the world, you would not see most of Earth's liquid fresh water. Far more fresh water is located underground than in all of Earth's rivers and lakes. How did this water get underground?

As the picture shows, when rain or snow falls some of the water soaks into the ground. The water trickles downward through spaces between the particles of soil and rock. Eventually, the water reaches a layer that it cannot move through. Then the water begins to fill up the spaces above that layer. Water that fills the cracks and spaces in underground soil and rock layers is called groundwater.