Great Lakes Research Paper

Geologic History of the Great Lakes About a billion years ago, a fracture in the earth running from what is now Oklahoma to Lake Superior generated enormous volcanic activity. Over a period of 20 million years, lava intermittently flowed from the fracture. This geomorphic process created mountains covering the regions now known as northern Wisconsin and Minnesota, and the Laurentian Mountains were formed in eastern Canada. Over time these mountains eroded, while occasional volcanic activity continued. Fluid magma below the highlands of what is now Lake Superior spewed out to its sides, causing the highlands to sink and form an immense rock basin that would eventually hold Lake Superior. In time, the fracture stabilized only after 570 million

and Canada, creating thousands of miles of ocean-like shores. The lakes also contain an estimated 35,000 islands. Officially dubbed "the nation 's fourth seacoast," the U.S. Great Lakes shoreline alone totals 10,210 miles (17,017 km), almost as long as the U.S. East, Gulf, and Pacific Coasts combined (about 11,323 miles or 18,223 km). As seen from space, the Great Lakes constitute one of the most identifiable features of the North American continent as well as our planet Earth. The North American Great Lakes are unique among the world 's large lakes, in that their basins are linked together and form one continuous drainage basin. Together, they constitute the greatest freshwater system on Earth, covering an area larger than Texas and about half the size of Alaska. The Great Lakes today hold an estimated six quadrillion gallons of water, a fifth, or 20 percent, of all the drinkable water on the surface of Earth. If all the water in the Great Lakes were spread evenly over the continental U.S., the 48 states would be flooded under more than nine feet of water. The water surface area of all the Great Lakes is 95,000 square miles (245,759 square km). The largest surface area of freshwater in the world. This would cover an area about the size of the state of Oregon. The water volume of the Great Lakes is 5,500 cubic miles (22,809 cubic km), 90% of U.S. supply, 18% of