A water cycle is the round-trip story of a raindrop. The cycle starts in oceans, seas, and lakes. When the sun shines, the air is warmed and it acts like a sponge. The heat of the sun slowly turns the water into a gas which is called water vapor. This process is called evaporation. Warm air is lighter than cold air, thus the cold air pushes the warm air upward. As it moves upward, currents of air develop; these air motions are called winds. When the warm, moist air passes over mountains, or when these warm air masses rise high above the earth, they are cooled. Cooling causes the water vapor to condense to the liquid form.
The raindrop is formed out of many condensed particles of water vapor. The condensations get heavier as they fall through more condensing water vapor, pulled toward the surface of the earth by gravity.
On the surface the raindrops may join many other raindrops, and if the earth cannot absorb them quickly, they form little streams or mighty rivers. Not all of the water will reach the sea. Some of it is drawn off into the air through evaporation where it starts on its cycle again, first forming a cloud and later falling as rain. But much of the water rushes on to some lake or sea before it starts its evaporation cycle again. A part of this rain soaks into the ground and is retained there in the capillary pores of the soil for plant use. Another part of it drains slowly into underground waterways or into rock crevices. After much time and slow motion, this water seeks lake, sea, or pond where it evaporates once more and becomes a cloud again. Then the whole cycle of the raindrop repeats itself. The water cycle is an important process to all plants and animals.
