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Nature's Water Cycle
Earth's oceans cover about 70 percent of all the earth's surface. They contain about 97 percent of all the water on earth, and are the source of most of the precipitation that falls to earth. Nature's water cycle begins with the sun's heat evaporating water from lakes, rivers, and especially, the oceans. About 85 percent of the vapor in the air comes from the oceans. But the salt is left behind during evaporation, and the precipitation that falls to earth is fresh water. This precipitation can be seen as several forms: rain, sleet, snow, and hail. This precipitation eventually drains into nearby lakes, rivers, or streams, and ultimately, returns to the oceans. This never-ending circulation of the earth's water makes a long journey from the oceans, to the air, to the land, and back to the oceans again. Because of nature's water cycle, there is as much water on earth as there ever was or ever will be. Water changes only from one form to another, and moves from one place to another. This is why it is essential to keep the water pure. |