Great Lakes Science

All though not technically a Great Lake, Lake St. Clair is in the Great Lakes Water System.  Three of the Great Lakes' waters flow through Lake St. Clair on their way east to the Atlantic Ocean.
Fun Facts - Taken From Naked Science on the National Geographic Channel
1/5 of the worlds fresh water is contained in the Great Lakes.
Much of North America would be arid without the Great Lakes
The Great Lakes are so large they are like inland seas.  Even relatively small Lake St. Clair is over 20 miles in each direction.  If you are at the ocean you can always tell a tourist from a Great Lake area.  You will hear them say, "Looks like the lake's a bit choppy today."
There is enough water contained in the Great Lakes that it could flood the entire continental United States to a depth of 9 feet.
The Great Lakes are so big that they make their own weather.
Lake Superior is 1300 feet deep in places and Lake Huron is 700 feet deep in places.
All 5 Great Lakes cover an area bigger than Utah.
Lake Michigan and Lake Huron provide Chicago and Detroit, over 10 million people, with drinking water.
Niagra Falls, part of the Great Lakes Water Ways, at its peak passes over 40 million gallons of water a minute and provides over 5 million homes with hydro-electric power.
Formation of the Great Lakes
There are two theories on how the Great Lakes were formed.  Both involve glaciers.
Theory 1
Evidence of the movement of a great ice sheet can be found on Kelly Island in Lake Eire.  They have found scaring over 15 feet deep, deep groves cut by the ice sheet.  The ice sheet is loaded with dirt, rocks and boulders that ground its way south creating the huge gouges at Kelly Island.  As the ice sheet melted it dropped its load of dirt, rocks and boulders forming the land masses surrounding the Great Lakes.
The ice sheet was 2 miles thick, exerting enormous grinding pressure, gouging out the lake basins.  It was capible of move about 3 feet a day.
The ice sheet lasted about 1 million years.  Ice rivers within the ice sheet moved much faster than the main ice sheet and was probably responsible for creating the lake basins.  Sediment from the first melt waters was so heavey that it block all light and created dead lakes.  This dead zone occured about 12,600 years ago.
Niagra Falls moves so much water that the Fall's cliff receeds 3 to 4 feet per year.  After much of the flow was diverted for the hydro-electric dams the rate of movement of the cliff toward Lake Eire has slowed to about 1 foot per year.
Theory 2
A new theory about the Great Lakes formation involves a meteor or comet that may have slammed into the ice sheet.
Alan West a geologist has been doing research on the shores of Lake Michigan.  He has found tiney, poppy sized grains of carbon.  He believes that the carbon came from an ancient forest that burned to the ground.  He also found that each grain of carbon contained thousands of micro-diamonds.
the micro-diamonds were formed when the grains of carbon underwent tremendous pressure, pressure he believes came from the impact of a meteor or comit.  He also discovered that the dirt in the area will cling to a magnet.  What causes this to happen is the presence of iridium.  Iridium is rare on earth.  It is commonly found in meteors and areas where they strike the earth.
It was found from fossil evidence that the Gulf of Mexico was a lot less salty at one time.  One theory is that the Great Lakes used to drain south through the Mississippi thus dumping large amounts of fresh water into the Gulf.
Nown Alan West believes that when his meteor struck the Great Lakes area it releases a massive amount of silt filled water into the rivers leading to the Mississippi.  The silt filled and blocked the rivers and the water was forced to find a new path, toward the east, creating the St. Lawrence River about 12,700 years ago.  This is the same time that the dead zone was created along the course of the Niagra River.  See theory above.
Shifting Water Levels
Another piece of evidence of glacier formation of the Great Lakes comes from data that shows that the water levels of the lakes is shifting.  The northern lakes were deeper and the southern lakes were shallower at an earlier time.  The ice sheet created 1 foot of earth compression for each 3 feet of ice.  The ice sheet would have been thicker in the north so the compression would have been greater.
As the ice sheet melted the ground level rebounded at about the rate of 1/10 inch/year.  This would cause the northern lakes to slowly rise and shift their water to the south.
Geologic evidence supports this.  Divers have found tree roots and branches in southern Lake Huron 2 miles off the shore of Lexington, Michigan.  Evidence that a forest existed in an area completely underwater now.

Shipwrecks (This excerpt taken from Wikipedia – subject – Great Lakes)

The large size of the Great Lakes increases the risk of water travel; storms and reefs are common threats. The lakes are prone to sudden and severe storms, particularly in the autumn, from late October until early December. Hundreds of ships have met their end on the lakes. The greatest concentration of shipwrecks lies near Thunder Bay (Michigan), beneath Lake Huron, near the point where eastbound and westbound shipping lanes converge.

The Lake Superior shipwreck coast from Grand Marais, Michigan to Whitefish Point became known as the "Graveyard of the Great Lakes". More vessels have been lost in the Whitefish Point area than any other part of Lake Superior.[12] The Whitefish Point Underwater Preserve serves as an underwater museum to protect the many shipwrecks in this area.

The first shipwreck was the Griffin, the first ship to sail the Great Lakes. Caught in a storm while trading furs between Green Bay and Michilimacinac, it sank during a storm[13] and has possibly been found.[14] The last major freighter wrecked on the lakes was the SS Edmund Fitzgerald, which sank on November 10, 1975, just over 30 miles (50 km) offshore from Whitefish Point. The largest loss of life in a shipwreck out on the lakes may have been that of the Lady Elgin, wrecked in 1860 with the loss of around 400 lives. In an incident at a Chicago dock in 1915, the SS Eastland rolled over while loading passengers, killing 841.

In August 2007, the Great Lakes Shipwreck Historical Society announced that it had found the wreckage of Cyprus, a 420-foot (130 m) long, century-old ore carrier. Cyprus sank during a Lake Superior storm on October 11, 1907, during its second voyage while hauling iron ore from Superior, Wisconsin, to Buffalo, New York. The entire crew of 23 drowned, except one, a man named Charles Pitz, who floated on a life raft for almost seven hours.[15]

In June 2008 deep sea divers in Lake Ontario found the wreck of the 1780 Royal Navy warship HMS Ontario in what has been described as an "archaeological miracle".[16] There are no plans to raise her as the site is being treated as a war grave.