1102 Great Lakes From Space
32x24 inches (81x61cm), AVHRR data. This group of five freshwater lakes, central North America, creating a natural border between the United States and Canada and forming the largest body of fresh water in the world, with a combined surface area of 95,000 sq mi (246,050 sq km). From west to east they are Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario, out of which flows the Saint Lawrence River. The international boundary passes approximately through the center of all the lakes except Lake Michigan, which lies entirely within the United States. The Great Lakes Basin is home to over 70 million inhabitants; it is also a unique fresh-water eco-system gradually recovering from high pollution levels caused by heavy industry around its shores. The Great Lakes were formed approximately at the end of the Pleistocene period, when the glacier-carved lake basins were filled with melt water from the retreating ice sheet. The lakes are connected to each other by straits, short rivers, and canals as clearly seen from space. The height above sea level of the lake surfaces varies from lake to lake; the greatest sudden drop occurs at Niagara Falls (167 ft/51 m). Ice closes most of the ports and winter storms hinder navigation. Some lakefront cities include Toronto, Hamilton, Buffalo, Cleveland, Detroit, Gary, Milwaukee, and Chicago. The opening of the St. Lawrence Seaway in 1959 has made the Great Lakes a truly international water body. The Great Lakes region, with its national parks and lakeshores, state parks, and many natural and scenic features, has become an important year-round recreation area.
