Jeff Holdener, age 9, of Lynn, Mass., for his question:
HOW WERE THE GREAT LAKES FORMED?
Largest group of fresh water lakes in the world are the five Great Lakes. They make up the most important inland waterway in North America.
About 250,000 years ago, a glacier moved south across the land of what is now the Great Lakes region. The glacier dug out deep depressions in the soft rocks of the area and picked up great amounts of earth and rocks.
The glacier withdrew from 11,000 to 15,000 years ago and the earth and rocks blocked the natural drainage of the depression. Water from the melting glacier gradually filled in the depressions and formed the Great Lakes.
Of the five lakes, only Lake Michigan lies entirely with the United States. The other four lakes are shared by the United States and Canada and form part of the boundary between the two countries.
The other four lakes, from the west to the east, are Lakes Superior, Huron, Erie and Ontario. The Boundary Waters Treaty of 1909 provides joint control of these four lakes between Canada and the United States.
Largest of the lakes is Lake Superior. In area, it is a little smaller than Maine and a little larger than South Carolina.
Second largest is Lake Huron which is almost as large as West Virginia. Next comes Lake Michigan which has an area equal to the combined areas of Maryland, Massachusetts and Delaware. Lake Erie, the shallowest of the lakes, is about the size of Vermont while the smallest, Lake Ontario, is not quite so large as New Jersey.
Some of the Great Lakes ports lie more than 1,000 miles inland, but ships can still sail from any of these ports to any other port in the world. This was made possible by three great sets of canals and locks built by the governments of the United States and Canada.
One set of canals, which together are called the Welland Canal, lies a short distance west of the Niagara River and connects Lake Erie and Lake Ontario. Ships sail from Lake Erie into Lake Ontario, down the Saint Lawrence River, and into the Atlantic Ocean.
Another set of canals is called the Soo, or Sault Sainte Marie Canals. These canals are on the Saint Marys River, which connects Lake Superior and Lake Huron. The Sault Sainte Marie system was built around rapids that occur at a 20 foot drop in the Saint Marys River. A third set of canals is the Saint Lawrence Seaway, which opened in June, 1959. The seaway extends 182 miles from Montreal to Lake Ontario. Its canals and locks enable ocean going ships to sail from the Atlantic to Lake Superior.
Ships may also reach the sea from the Great Lakes by two other routes. One is by the New York State Barge Canal System from Buffalo, N.Y., to Albany, N.Y., connecting Lake Erie with the Hudson River and the Atlantic Ocean.
Another route takes ships from Lake Michigan to the Gulf of Mexico by way of the Chicago Sanitary and Ship Canal, through the Illinois River, and down the Mississippi River.