Dear Tom,
At an ocean beach it is plain to see tidal action. The water rolls in and back out because of the moon’s gravitational pull. I suppose, because of Lake Michigan’s size, it might also have a tide. Is it measurable? If so, what is its cycle?
John Goldsmith, Chicago
Dear John,
Lake Michigan, like all bodies of water, is affected by the gravitational pull of the moon (and the sun), and it does indeed experience tides. However, they are miniscule compared to their ocean counterparts.
Tides in Lake Michigan range from about one-half inch to one and one-half inches in height and, just as on ocean shores, occur twice daily. Such small variations are completely masked by wave action at the beaches and by other short-period water-level fluctuations caused by wind and changes in air pressure.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Place, Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
