Scott Leach, age 14, of West Hill, Ontario, Canada, for his question:
HOW WAS NIAGARA FALLS FORMED?
The Niagara River connects Lake Erie and Lake Ontario. The waterway also forms the international boundary line between the state of New York and the Canadian province of Ontario. With the exception of Lake Ontario, all of the Great Lakes empty into this Niagara River which is only about 35 miles long. On the river is the world famous Niagara Falls.
Niagara Falls is rated as one of the world's most beautiful natural regions and also as one of its most important waterfalls. It is also a popular tourist center.
Scientists say that Niagara Falls is not much more than 20,000 years old. This is considered to be young by geological standards, when you realize the Grand Canyon in Arizona is millions of years old.
The falls were formed after the last great ice sheet withdrew. The ice changed the surface of the land so much that waterways and streams were forced to seek new channels. The waters of Lake Erie, for example, overflowed and formed the new Niagara River. On its way north, the river passed a high cliff called the Niagara Escarpment. The water cut away both hard and soft rock.
About 200,000 tons of water spill over Niagara Falls each minute of the day and night. The water drops in two streams: the larger over a rocky ledge of Niagara limestone on the Canadian side which is called the Horseshoe Falls, and a smaller stream to the east which is called the American Falls. Horseshoe Falls is 158 feet high and 2,600 feet wide while the American Falls is 167 feet high and about 1, 000 feet wide.
The shape of the falls change from year to year. Since 1678, Horseshoe Falls has eroded about a quarter of a mile, while the American Falls has receded about 90 feet. Each year the edge of Horseshoe Falls moves back about three feet while the American Falls moves back from between four and seven inches each year.
About 80,000 tons of rock fell from the face of the American Falls in 1931 and a few years later 30,000 tons of rock cracked off the upper edge of the Horseshoe Falls. In 1954 185,000 tons of rock fell from the American Falls in the largest slide ever to occur at Niagara Falls.
In 1969 a team of U.S. Army engineers built a dam to temporarily stop the flow of water over the American Falls. They did this so scientists would have a chance to study the rock ledge and find a way to prevent further serious erosion.
Niagara Falls was used to run a sawmill as early as 9757. In 1881 the first hydroelectric power was generated at the Falls but the first generators for the large scale production of electric power weren't installed until the mid 1890s.
Today large power plants line both sides of the river. The Sir Adam Beck generating plants on the Canadian side have a capacity of 1.8 million kilowatts. On the American side, one of the world's largest hydroelectric facilities, completed in 1962, has a capacity of 2.2 million kilowatts: