The Great Lakes

Explore the physical properties of the world’s largest freshwater system, the so-called sweet-water seas. Every nook and cranny of this Wisconsin Sea Grant site has a Great Lakes focus. This topic page, in particular, drills down into the physical characteristics of the lakes. The following sections will explain the formation of the Great Lakes, and their current depth, shoreline attributes, temperature and more.



The Formation of the Great Lakes

How They Were Made
Thousands of years ago, the melting mile-thick glaciers of the Wisconsin Ice Age left the North American continent a magnificent gift: five fantastic freshwater seas collectively known today as the Great Lakes -- Lake Superior, Lake Huron, Lake Michigan, Lake Erie and Lake Ontario. Read more...


Lake Superior
The greatest of the Great Lakes is Lake Superior, the northernmost and westernmost Great Lake -- and the biggest, the deepest, the coldest and the most pristine. Read more...


Lake Huron
The second-largest Great Lake, Lake Huron, has a surface area of 23,000 square miles -- slightly smaller than West Virginia -- making it the fifth-largest freshwater lake in the world. Read more...


Lake Michigan
Lake Michigan is the third largest Great Lake and the fifth largest lake in the world. Bordered by Wisconsin, Illinois, Indiana and Michigan, it is the only Great Lake that lies entirely within the boundaries of the U.S. Read more...


Lake Erie
Lake Erie is the fourth-largest Great Lake and the world's twelfth largest freshwater lake. Erie is about 210 miles long, 57 miles wide and about 570 feet above sea level. Read more...


Lake Ontario
The opposite of Lake Superior in almost every way, Lake Ontario is the easternmost, lowest in elevation, smallest in surface area and perhaps the most polluted Great Lake. Read more...


Photo Gallery
Great Lakes landscapes, cities, islands, bays and more. Read more...


Wisconsin Great Lakes Facts

Just 3 percent of the world's water exists as fresh water...
...2 percent is locked in the polar ice caps; less than 1 percent resides in freshwater lakes and streams.


The Great Lakes contain an estimated 5,500 cubic miles...
...(22,700 cubic kilometers) of water — a fifth of all the liquid surface fresh water on Earth.


The United States draws more than 40 billion gallons...
...(151 billion liters) of water from the Great Lakes every day — half of which is used for electrical power production.


About 6.4 million acres...
...(2.6 million hectares) of Lakes Michigan and Superior lie within Wisconsin's state boundaries.


Wisconsin's 15 coastal counties...
...contain more than 1.2 million acres of wetlands (486,000 hectares) — nearly a fourth of all of the state's remaining wetlands.


Wisconsin has more than 800 miles...
...(1,300 kilometers) of Great Lakes coastline.


More than a third of Wisconsin's population...
...lives in the 11 counties forming its Lake Michigan coast; 24 percent live in the three southeast coastal counties of Milwaukee, Racine, and Kenosha alone.


About 13 million salmon and trout...
are stocked in Lake Michigan each year by the Wisconsin Department of Natural Resources.


Anglers net more than 500,000 trout and salmon...
...each year in Wisconsin waters of Lakes Michigan and Superior.  Great Lakes trout and salmon fishing stamp fees alone bring in $1.7 million a year to state coffers.


The Great Lakes have been colonized by 161 known nonindigenous aquatic species...
...over half of them since the opening of the St. Lawrence Seaway in 1959.


Wisconsin's power and water utilities...
...spend an estimated $5 million annually trying to protect water intakes from zebra mussels.


The assessed value of Lake Michigan lakeshore property...
...in just one Wisconsin county — Door County — is almost $2 billion.


Each year, Wisconsin's 12 active harbors...
...on lakes Michigan and Superior handle a total of more than 40 million tons (40 billion kilograms) of commodities valued at more than $7 billion.


More than 800 toxic contaminants...
...have been identified in Great Lakes water and sediment.


Five of the 43 Great Lakes "Areas of Concern"...
...identified by the U.S.-Canadian International Joint Commission are in Wisconsin — Superior Bay, Menominee River, Green Bay, Sheboygan River, and Milwaukee estuary.


Great Lakes Weather

Weather on the Great Lakes
The National Weather Service maintains graphic representations and data-rich information on the weather and navigational properties of the lakes. Read more...


Real-Time Lake Conditions
The Great Lakes Observing System provides real-time information lake conditions. Read more...


Water Levels on the Great Lakes

Why the Lake Levels Fluctuate
This brief explanation from the National Oceanic and Atmospheric Administration explains with the levels of the lakes varies and what affect that has on ecosystems and on development around the lakes. Read more...


Videos

Are Flame Retardants Harming Frogs?
In Dr. William Karasov's lab, the northern leopard frog is front and center in a series of research experiments designed to explore how environmental toxins may be affecting the frog's immune system, growth and development.
Read more...


Climate Change: A Great Lakes Regional Perspective - Magnuson
A talk by John Magnuson
Emeritus Professor of Zoology and Limnology, UW-Madison on June 7 & 11 in Superior and Milwaukee, Wisconsin
Read more...


Revitalizing Local Waterfront Economies
This video outlines the Great Lakes Legacy Act and highlights benefits it brings to communities. Read more...


Welcome Jane Harrison, Our First Social Scientist
Wisconsin Sea Grant welcomes social scientist Dr. Jane Harrison to our staff. Read more...


A Message from the Director
Dr. Anders Andren welcomes you to our Website and describes what Sea Grant does. Read more...


A Tour of the "Northerner"
Check out a historic Lake Michigan shipwreck without getting wet. Read more...


Beyond the Usual Suspects
E. coli bacteria sometimes contaminates the waters of Bradford Beach in Milwaukee. Where does it come from? How can it be reduced? Dr. Sandra MacLellan cracks the case. Read more...


Engineering Students Dive into Field Work
Wisconsin Sea Grant Coastal Engineering Specialist Gene Clark describes slope stability, erosion, and other coastal issues as students learn to deploy and operate instruments. Civil and Environmental Engineering Professor Chin Wu conducted the class, called "Exploration and Investigation of Coastal Processes in the Great Lakes and Inland Lakes." Read more...


See More videos on the Great Lakes
Read more...


Related Publications

Visit Our Publication Store
For publications related to the history of the Great Lakes, see our publications store. Read more...


Related Websites

Gifts of the glaciers
Thousands of years ago, the melting mile-thick glaciers of the Wisconsin Ice Age left the North American continent a magnificent gift: five fantastic freshwater seas collectively known today as the Great Lakes - Lake Superior, Lake Huron, Lake Michigan,  Lake Erie and Lake Ontario. Read more...


Glossary of the Great Lakes
Minnesota Sea Grant has prepared this reference site about environmental programs, agencies and terminology related to the Great Lakes. Read more...


Great Lakes Information from the Environmental Protection Agency
The Great Lakes - Superior, Michigan, Huron, Erie and Ontario - are an important part of the physical and cultural heritage of North America. Spanning more than 750 miles from west to east, these vast inland freshwater seas have provided water for consumption, transportation, power, recreation and a host of other uses. Read more...


Wisconsin's Water Library
Established in 1964 by the UW Water Resources Institute, Wisconsin's Water Library (formerly known as the Water Resources Library) is unique among UW-Madison's many libraries for its collection of almost 30,000 volumes of water-related information about the Great Lakes and the waters of Wisconsin. The library includes a curriculum collection, dozens of educational videos, a children's collection, and more than 20 journals and 100 newsletters. Read more...

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