By surface area, Lake Huron is the second-largest of the Great Lakes, with a surface area of 23,000 square miles (59,600 km2) making it the third-largest fresh water lake on Earth (and the fourth-largest lake, if the Caspian Sea is counted as a lake).[1] By volume however, Lake Huron is only the third largest of the Great Lakes, being surpassed by Lake Michigan in this aspect.[4] When measured at the Low Water Datum, the lake contains a volume of 850 cubic miles (3,540 km3) and a shoreline length (including islands) of 3,827 miles (6,157 km).[1]

The surface of Lake Huron is 577 feet (176 m) above sea level.[2] The lake's average depth is 195 feet (59 m), while the maximum depth is 750 feet (229 m).[2] It has a length of 206 miles (332 km) and a greatest breadth of 183 miles (295 km).[2]

Important cities on Lake Huron include: Goderich, Sarnia, Bay City, Alpena, Rogers City, Cheboygan, St. Ignace, and Port Huron.[citation needed]

A large bay that protrudes northeast from Lake Huron into Ontario, Canada is called Georgian Bay. A notable feature of the lake is Manitoulin Island, which separates the North Channel and Georgian Bay from Lake Huron's main body of water. It is the world's largest freshwater island.[5] A smaller bay that protrudes southwest from Lake Huron into the state of Michigan, U.S.A. is called Saginaw Bay.

[edit] Water levelsHistoric High Water The lake fluctuates from month to month with the highest lake levels in October and November. The normal high water mark is 2.00 feet (0.61 m) above datum (577.5 ft or 176.0 m). In the summer of 1986, Lakes Michigan and Huron reached their highest level at 5.92 feet (1.80 m) above datum.[6] The high water records began in February 1986 and lasted through the year, ending with January 1987. Water levels ranged from 3.67 to 5.92 feet (1.12–1.80 m) above Chart Datum.[6]

Historic Low Water Lake levels tend to be the lowest in winter. The normal low water mark is 1.00 foot (30 cm) below datum (577.5 ft or 176.0 m). In the winter of 1964, Lakes Michigan and Huron reached their lowest level at 1.38 feet (42 cm) below datum.[6] As with the high water records, monthly low water records were set each month from February 1964 through January 1965. During this twelve month period water levels ranged from 1.38 to 0.71 feet (42–22 cm) below Chart Datum.[6]

[edit] Great Lakes Circle TourThe Great Lakes Circle Tour is a designated scenic road system connecting all of the Great Lakes and the St. Lawrence River.[7]

[edit] Geology