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Grand Haven students participate in annual fishing event
Grand Haven Tribune (5/15)
In Michigan, Grand Haven Area Public Schools partnered with a nonprofit organization called Pursuing a Dream to give about 300 students with special needs the opportunity to fish and enjoy the outdoors.

NYPA funding aids three St. Lawrence River projects
Watertown Daily Times (5/10)
The St. Lawrence River Research and Education Fund has provided funding for three projects that support environmental education in and around the riverís ecosystem.

Lake Michigan Academy students learn from 'Salmon in School' project
MLive (5/9)
About 100 schools throughout Michigan are selected to take part in the Lake Michigan Academy program that aims to help stock local rivers and support fishing as a leisure activity.

Huron Perth students find Lake Huron threats
Blackburn News (5/1)
Nearly 60 high school students from the public and separate boards in Huron and Perth counties spent one day at the Oakwood Inn in Grand Bend, Ontario, where they were learning about the environmental threats and challenges to Lake Huron.

TEACH Calendar of Events
What's going on in your neighborhood this month? Meet other people and learn together at recreational and educational events! Our new dynamic calendar is updated daily with current educational events.
TEACH Questions & Answers

Do the Great Lakes freeze in the winter?
from Debbie in Olyphant, Penn., Michael in Kenosha, Wisc., and Jim in St. Clair Shores, Mich.

The Great Lakes do freeze, but not completely. According to Ray Assel of the Great Lakes Environmental Research Laboratory, ice cover on the Great Lakes varies from lake to lake and year to year. For example, in a year with normal temperatures, 25 percent of Lake Ontario will be frozen over, while up to 90 percent of Lake Erie will be frozen. However, wind and water movement over bodies of water as large and deep as the Great Lakes make it unlikely the lakes have ever frozen over completely for any significant length of time.

The Great Lakes have come close to freezing over completely during the extremely cold winters of 1976-77, 1977-78 and 1978-79, with up to 90 percent ice coverage. However, Assel says that severe winter air temperatures are not necessary for large ice cover on the lakes. A cool summer and fall can result in below normal water temperatures by late fall. Extensive ice cover can then form with only average winter temperatures.

Old Ice bridge As for the Niagara Falls, the volume and speed of the water flowing over the falls prevents them from freezing, as does the ice-boom at the mouth of Lake Erie. The ice-boom is a series of floating steel pontoons extending across the river from Buffalo, New York to Fort Erie, Ontario. It prevents ice from clogging the river and hydroelectric intakes by helping an "ice bridge" (a stable ice cover) to form at the mouth of Lake Erie. Before the installation of the ice-boom in 1964, the American side of the falls froze over in 1909, 1938 and 1949 because ice jams upstream reduced the water flow. Ice bridges can also form below the falls when ice goes over the falls and freezes to the edges of the gorge, resulting in a buildup of ice (as thick as fifty feet in some places) stretching across the entire river. For photographs of historical ice bridges on the falls, go to Edsen Breyer's Postcard Museum.

For a look at current and historical Great Lakes surface and ice cover, go to GLERL's Great Lakes Surface Environmental Analysis pages.

Thank you for your questions!

References
Nilsson, Matt. Not Easy to Freeze. Earthwatch Radio, 1/25/00.
Niagara Falls, Thunder Alley.


Answered on January 8, 2001

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