ice "boulders" in Lake Michigan

Passed along in email during this cold snap:

Visitors to the shores of Lake Michigan were greeted by an interesting sight this week, as waves lapped against hundreds of massive ice balls.
The balls, or boulders, as some have called them, are formed when water from the lake begins to freeze and is pushed ashore by wave action, according to AccuWeather.com Meteorologist Jim Andrews.

No one seems to have offered a measurement and it's a bit hard to get perspective and the event is described as not all that unusual, but still ....