Water Resources - Lake Michigan
Lake Michigan Facts
Lake Michigan is the fourth largest freshwater lake in the world based on surface area. Only Lakes Superior, Victoria (in Africa), and Huron (but just slightly) are larger. Lake Michigan covers 22,278 square miles. It is 307 miles long and 118 miles wide at Petoskey (which is the widest point). Including islands, Lake Michigan's shoreline is 1,659 miles long.
Another way to measure lake size is volume. Lake Michigan has the fifth largest volume of any freshwater lake. Only Lakes Baikal (which is in Russia, is the world's deepest at one mile, and by itself contains another fifth of the earth's freshwater), Tanganyika (Africa), Superior, and Nyassa (Africa) are bigger. Lake Michigan contains about 1,180 cubic miles of water.
Lake Michigan has a maximum depth of 924 feet, with an average depth of 279 feet. Interestingly, this puts the deepest spot (which is located mid-lake near the Michigan coastal cities of Frankfort and Manistee) about 350 feet below sea level! This may seem quite deep, but actually Lake Michigan ranks far down on the list of the world's deepest lakes.
Lake Michigan is a dynamic system. Winds blowing across a hundred or more miles of water can create large ocean-like waves, especially during fall or winter storms. Waves 20 or more feet in height on the open waters of the Lake have been recorded. These waves can create strong long-shore currents, stir up near shore bottom sediments, erode shorelines, and sink freighters! The Petoskey waterfront is a good place to watch huge storm waves overrun the breakwall and light beacon.
Strong winds or sudden changes in barometric pressure over different sections of the Lake can cause the surface of the Lake to literally tilt, piling up water against one shore and causing a corresponding drop on the opposite shore. This storm-induced tilting can be up to three feet high on Lake Michigan. When the storm abates, the tilt oscillates back and forth across the Lake for a long time before it is dampened by friction. This back and forth oscillation, kind of like water sloshing in a bathtub, is called a seiche. The time for a seiche to complete one back and forth oscillation can be from 30 minutes to several hours. Usually there is some kind of seiche action happening on the Lake, although it is usually only about several inches in amplitude. Sometimes, people confuse seiche action with tides. Although lunar forces act on Lake Michigan's waters the same as they do on the oceans, because of its relatively small size, tides are almost imperceptible--only a fraction of an inch.