Joseph Marra, age 9, of Elnora, New York, for his question:
How do lakes form?
A lake is a giant puddle with enough water to fill a hollowed out basin in the earth. As a rule, a few friendly streams empty in enough water to keep it filled ¬and other streams lead some of the water away to keep it from overflowing. Each lake has a different story to tell about its birth an exciting story of how the hollow basin formed in the ground and how it happened to fill with lake water.
The earth creates lots of lakes, large and small. But she does not intend them to live as long as her mighty mountains. Most of our brimming lakes will be swamps or dry land 100,000 years in the future. By that time, other basins will be hollowed in the earth and filled with lake water. Some will form on high slopes where melting water runs down from glaciers on the lofty mountain peaks. Others will form around flat glaciers, where melting water fills hollows already there in the ground.
Other future lakes will form where earthquakes and landslides change the ups and downs of the ground. Sometimes earthquakes .cause the ground to sink and form a hollow trough. If this basin happens to be near a stream or river, the water is likely to drain down and fill it with lake water. Sometimes a landslide falls across a river and stops its flow with a mighty wall of rocks and gravelly dirt. Then the water collects and forms a lake behind the landslide.
A few future lakes will form in deep hollows at the tops of mountain peaks. As a rule, these mountains are dead or sleeping volcanos and the hollows are the craters that once poured forth streams of molten lava. Rains and melting snows collect in these high hollows and form some of the world's most lovely lakes.
Many other smallish lakes will be formed by wandering rivers who change their minds. A river, of course, always flows gently downhill to meet the waters of the ocean. It may flow fast down steep steep slopes or take its time flowing lazily across a flat plain. A lazy river is more likely to form lakes. As it goes, it tends to weave from side to side in snakey loops. Sometimes its flowing water digs a new channel and makes a shortcut across a curve. This cuts off a loop and the water it holds is left behind as a lake. Other lakes will form in hollows created when underground caves collapse.
The earth has many ways to form lakes and we also can create them. Our clever engineers do this when they build a dam across a river. Most of the flowing water is stopped in its tracks and guided to fill a reservoir. Our reservoirs are man made lakes.
During its lifetime, a lovely lake is a wondrous thing. Fishes, frogs and countless creatures thrive in its fresh water. Sedges and bullrushes grow around its brinks, water birds nest there, and all the animals of the neighborhood come tip toeing down to drink. The earth expects it to last perhaps 50,000 years. It is very sad when the human population dumps in trash and pollution that chokes and kills a lovely lake in 20 years or so.