4 Earth is sometimes called the Blue Planet because most of it is covered by water Most of that water is salt water about 97 5 percent People and many other living things how ever need fresh water to live Fresh water has little salt in it Luckily there are freshwater lakes rivers and glaciers Another source though can not be seen About 30 percent WATER WATER EVERYWHERE Liquid water is one of the essential elements for life on Earth
5 of Earth’s fresh water is underground Some of this comes out of the ground as natural springs Hot springs and geysers are two types of natural springs that reveal much about what goes on beneath Earth’s surface They tell us about the intense heat of inner Earth about volcanic activity and about other forces at work in nature Hot springs and geysers are also popular places for people to visit People and all life need fresh water to live In what ways do you use fresh water THINK ABOUT IT Areas of the Atacama Desert of South America get no rainfall However underground water comes to the surface through geysers
6 A spring is a place where water naturally flows from the ground Springs develop when rainfall sinks through the soil to the rocks beneath Some kinds of rock are porous or full of little holes like sponges and they absorb the water Other rocks have cracks that allow the water to trickle through to lower lay ers of rock Sometimes this The Vaucluse spring is the largest spring in France Its waters are the source of the Sorgue River WHAT ARE SPRINGS
7 underground water is under pressure and seeps upwards through an opening in level ground A spring may come out of dry ground or into a stream lake or sea A hot spring or thermal spring is a spring with a water temperature much higher than the average air tem perature of the surrounding area Some hot springs emerge powerfully with so much force that they eject tall columns of water and steam These are called geysers Thermal means involving affected by or producing heat VOCABULARY The Mammoth Hot Springs are in Yellowstone National Park Their flowing waters helped shape the land over thousands of years
