the great lakes
They are a dominant part of the physical and cultural heritage of North America. Glacial clays and organic sediments occur in the deep areas. Studies in the Lake Superior region indicate that a river system and valleys formed by water erosion existed before the Ice Age. See if your knowledge of names is nimble—or numb—in this quiz of states and cities. Great Lakes, chain of deep freshwater lakes in east-central North America comprising Lakes Superior, Michigan, Huron, Erie, and Ontario. The Great Lakes are, from west to east: Superior, Michigan, Huron, Erie and Ontario. Although Lake Baikal in Russia has a larger volume of water, the combined area of the Great Lakes—some 94,250 square miles (244,106 square kilometres)—represents the largest surface of fresh water in the world, covering an area exceeding that of the United Kingdom. As the ice sheet melted and receded about 14,000 years ago, the first segments of the Great Lakes were created. Individually, the lakes rank among the 14 largest in the world (see table). This system extends generally eastward from the St. Louis River in Minnesota (which flows into Lake Superior), through the lakes and the St. Lawrence River, and empties into the Atlantic Ocean at the Gulf of St. Lawrence. As the ice retreat continued, Lake Maumee was drained into Lake Chicago through a valley that now contains the Grand River in Michigan. The age of the Great Lakes is still not definitely determined. A wide range of rock types and deposits are found in the Great Lakes because of their broad area and glacial origin. As the ice sheet retreated, low-lying, glacially depressed areas, such as the region to the east of Georgian Bay, were exposed. The Great Lakes form the western portion of the larger St. Lawrence hydrographic system. Their drainage basin of about 295,710 square miles (which includes the areas of the lakes themselves and their connecting waterways) extends approximately 690 miles from north to south and about 860 miles from Lake Superior in the west to Lake Ontario in the east. More than 20% of all the world’s freshwater is in the Great Lakes. These may change slightly as more detailed mapping is completed for these watersheds. Except for Lake Michigan, the lakes provide a natural border between Canada and the United States, a frontier that was stabilized by a boundary-waters treaty of 1909. Although the Great Lakes are large, they are sensitive to pollutants. Concern over the fate of the lakes reached a high pitch in the late 20th century, with both the U.S. and the Canadian governments and individuals investigating methods for reversing the consequences of years of misuse of the lakes’ waters. The maps also display the counties in the Great Lakes basin. They are one of the great natural features of the continent and of the Earth. The glaciers undoubtedly scoured these valleys, widening and deepening them and radically changing the drainage of the area. Omissions? You may be familiar with New York and Nebraska, but are there 11 U.S. states with names that begin with the letter "N?" The lakes have not benefited from this development, however, and have been seriously affected by pollution. The present configuration of the Great Lakes basin is the result of the movement of massive glaciers through the mid-continent, a process that began about one million years ago during the Pleistocene Epoch. United States Environmental Protection Agency, The Great Lakes Atlas Third Edition 1995 is available from NSCEP, US EPA's publication service, Data and Map Floor Studies of the Great Lakes from NOAA's Great Lakes Environmental Research Laboratory, 84% of North America's surface fresh water, about 21% of the world's supply of surface fresh water, Nearly 25% of Canadian agricultural production and 7% of American farm production, Population is more than 30 million people - roughly 10% of the U.S. population and more than 30% of the Canadian population. The Great Lakes are one of the world’s largest surface freshwater ecosystems. They are a dominant part of the physical and cultural heritage of North America. Premium Membership is now 50% off! The weight of the ice sheet exerted enormous pressures on the Earth’s crust. Estimates range from 7,000 to 32,000 years of age. The ancient rocks of the Canadian Shield cover part of the Superior and Huron basins, while Paleozoic sedimentary rocks make up the remainder of the basins. After the weight of the ice was removed, the land (i.e., the outlet to the lakes) began to rise, closing off some outlets and allowing the water levels of the lakes to slowly rise. Great Lakes, chain of deep freshwater lakes in east-central North America comprising Lakes Superior, Michigan, Huron, Erie, and Ontario. The last glaciation in North America is called the Wisconsin Glacial Stage because it left many fresh landforms and sediments in that state. Lake Superior 82,000 sq km, 31,698 sq miles in size, is the largest fresh water lake in the world. There are limestone outcrops and large deposits of sand and gravel, usually near shore. Fort Dearborn - Future Chicago, largest city on the Great Lakes, 3rd largest city in the US, located in reality at the southwest end of Lake Michigan displayed a couple hundred miles north near Green Bay Wisconsin. The Alliance for the Great Lakes is a nonpartisan nonprofit working across the region to protect our most precious resource: the fresh, clean, and natural waters of the Great Lakes. For a discussion of the system east of Lake Ontario, see Saint Lawrence River and Seaway. Updates? By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. Eventually, drainage to the east and into the Atlantic Ocean was established, at one time down the valleys of the Mohawk and Hudson rivers and then along the course of the upper St. Lawrence River. Adjunct Professor, School of Public Health, University of Michigan, Ann Arbor.... Marquette Harbor Lighthouse on Lake Superior, Marquette, Michigan. The Great Lakes and St. Lawrence River hold 20 percent of the earth’s fresh surface water or 6 quadrillion gallons, cover a total area of 246,463 square kilometers or 95,160 square miles, and with the St. Lawrence River span 3,700 km (2,342 miles) or almost half of the North American continent. It is estimated that there are nearly … Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario, form the Great Lakes, straddling the United States and Canada to make up the largest group of freshwater lakes … Outflows from the Great Lakes are relatively small (less than 1 percent per year) in comparison with the total volume of water. The Great Lakes have a total shoreline near 10,000 miles, over 350 species of fish, and provide drinking water for over 40 million people. It is about 350 miles (565 km) long and 160 miles (257 km) at its widest point. The Great Lakes were born when glaciers receded from this part of the world at the end of the last ice age. https://www.britannica.com/place/Great-Lakes, National Wildlife Federation - Great Lakes, North America, U.S. Environmental Protection Agency - Great Lakes, LiveScience - Great Facts About the Five Great Lakes, Great Lakes - Children's Encyclopedia (Ages 8-11), Great Lakes - Student Encyclopedia (Ages 11 and up). Detail map of northeast portion of the Great Lakes Basin. The Clean Water Act defines the orange striped polygon on the US side as part of the Great Lakes basin (though hydrologically it drains into the St. Lawrence River). Best Great Lakes Bay Resorts on Tripadvisor: Find traveler reviews, candid photos, and prices for resorts in Great Lakes Bay, Michigan, United States. At one high-water stage, the waters of the Huron and Michigan basin formed one large lake—Lake Algonquin. Learn more about threats to the Great Lakes and how you can make a difference. The Great Lakes basin encompasses large parts of two nations, the United States and Canada. The Great Lakes are, from west to east: Superior, Michigan, Huron, Erie and Ontario. Save 50% off a Britannica Premium subscription and gain access to exclusive content. The map at the start of episode 1 showed the locations of 2 of the 3 largest cities on the Great Lakes in the wrong places. It is generally accepted that Lake Erie reached its present level about 10,000 years ago, Lake Ontario about 7,000 years ago, and Lakes Huron, Michigan, and Superior some 3,000 years ago. Black Friday Sale! Water began filling the glacially scoured basins as soon as the ice receded, some 14,000 years ago. Our editors will review what you’ve submitted and determine whether to revise the article. Lake Chicago, in what is now the southern Lake Michigan basin, and Lake Maumee, in present-day western Lake Erie and its adjacent lowlands, originally drained southward into the Mississippi River through the Illinois and Wabash drainages, respectively. The Great Lakes basin is defined by science, engineering and politics. Pollutants that enter the lakes are retained in the …
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