The Great Lakes are bodies of fresh water, making them one of North America’s greatest natural resources. Natural forces formed the Great Lakes and they contain many physical features including marshes, dunes and beaches. These lakes continue to shape the features of their watershed through different level fluctuations which effects on our ecosystem.

Great Lakes
Low Water
Stretching more than 9,500 miles, the shores of the Great Lakes are constantly reshaped by the effects of wind, waves and moving water. Erosion is a natural process that occurs under all water level conditions, although it is often magnified during periods of high water or storms.
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Glaciers
Six hundred million years ago, during the Paleozoic Era, central North America was covered by a shallow sea. This sea deposited a lot of sand, salts, and silts, which, after time, were compressed into limestone, sandstone, shale, halite, and gypsum.
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sand dune
The sand dunes of the Great Lakes region represent the largest freshwater coastal dunes in the world. These dunes, such as the Sleeping Bear Dunes on the northeastern shore of Lake Michigan, are only 3,000-4,000 years old - that's very young, geologically speaking!
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Water Flow
In areas of high-density development, minor deviations from long-term average water levels can produce pronounced economic losses. In less developed areas, impacts can be less noticeable.
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Great Lakes Coast
About a billion years ago, a fracture in the earth running from what is now Oklahoma to Lake Superior generated volcanic activity that almost split North America. Over a period of 20 million years, lava intermittently flowed from the fracture.
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beach
The most common type of shoreline in the Great Lakes region is the sand beach. Sand is deposited on beaches when the waves from the lake move it up from the lake bottom to the shoreline, and the sandy shorelines are ever changing.
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wetland
The freshwater wetlands of the Great Lakes' coasts are unique in ecological character, size and variety. They range from small wetlands nestled in scattered bays to extensive shoreline wetlands such as those of southwestern Lake Erie, freshwater estuaries of northern Wisconsin and the enormous freshwater delta marshes of the St. Clair River.
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Wisconsin topographic map
During the Ice Age, mile-thick sheets of ice covered the Great Lakes region multiple times depressing the crust with their weight. Ancient beach ridges mark previous lake shorelines. Since glaciers retreated (about 10,000 years ago), Earth’s crust has been adjusting upward in a process of isostatic rebound that continues today.
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Indigo blue wind ruffled waves of Lake Huron
Water levels on the Great Lakes change seasonally each year and can vary dramatically over longer periods. Short-term changes are generally of greater magnitude than the monthly averages.
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stairs to lake michigan
Water levels are part of the ebb and flow of nature. Learn about the three types of water level fluctuations, how levels are measured on the Great Lakes, and what's causing the recent drop.
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Great Lakes at a Glance

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