Sharon Green, age 12, of Fredericton, N. B. for her question:
Why don’t the oceans overflow?
The rivers empty millions of tons of water into the oceans every day. Rain, snow and sleet fall into the sea adding still more water. It is natural to wonder, then, why does not the ocean fill up and overflow. This does not happen because of the water cycle and everything, absolutely everything in our world plays a part in this merry go round. The powerhouse which keeps the water cycle going is the mighty sun.
Every day, the sun smiles down on some part of our world wide ocean. Its warm sunbeams heat up the surface water. Countless tiny molecules get enough energy from the sunshine to break loose from the watery seas. They fly off into the air as separate particles of water vapor. Every day, tons of water evaporate into gas. The water which evaporates is just about equal to the water which is poured into the sea from rivers, rain and other sources.
Does this mean that all the water an the earth will some day be vapor in the air? Not at a11. The air keeps it so long and no longer. Warm air.. can hold more water vapor than cool air and, as everyone knows, the air blows hot and cold, Warm air containing its full quota of vapor sooner or later becomes cool. When this happens, it must give up some of its vapor.
The vapor, which is a gas, is turned into tiny droplets of liquid water. These tiny droplets make mist, the mist from which clouds are made. The water which evaporated from the ocean is now a cloud, a flying carpet wafted on the breezes over land and sea.
The droplets in the cloud are light enough to float in the air but not light enough to stay aloft for ever. Sooner or later the droplets dell to form raindrops and come tumbling down again.
The water evaporated up from the sea may travel many, many miles before it falls down again as rain. And a certain amount of rain falls everywhere on the globe. The water cycle is not over, even after the rain falls, On land, some of it seeps into the soil or trickles through porous rocks. Some of it is used to supply the moisture needed by plants. It may help a lettuce to grow or it may be carried up to the top of a giant redwood tree. Some of the fallen rain runs into reservoirs to supply us with drinking and washing water.
The rest of the fallen rain runs off to loin the sea once more Little streams run giggling down the muntain slopes. Some are in such a hurry that they somersault over steep waterfalls and tumble through rollicking rapids. Little streams loin to make bigger streams. Big streams loin to make rivers. 'The rivers swish their taffeta skirts, always wending on, on to loin the sea. But they are only 'returning some of the water which was drawn up from the ocean by the warm sun. Some of the water they return will again evaporate, become clouds, fall as rain and run back to sea as part of the endless water cycle.