Lake Michigan Ice Boulders, photo by Leda Olmsted
Todays post is from the “Ain’t it Cool” Department. A couple of weeks ago Leelanau County resident Leda Olmsted was walking the Lake Michigan shore in the Sleeping Bear Dunes National Lakeshore when she came across this incredible scene. TV 7&4 reports in Ice boulders roll onto shores of Lake Michigan that Leda took some photos, uploaded to the news station’s Facebook and:
Leda says she was shocked by the response. Olmsted explains, “From there it got like 800 shares and thousands of likes and overnight I had Good Morning America and The Weather Channel calling me, so it has been a really crazy weekend!”
Deputy Superintendent from the Sleeping Bear Dunes National Lakeshore Tom Ulrich says, “It’s not that it never happens and this is a once in a decade thing, it happens more often than that, but these are very large and got bigger than they normally get.”
The ice balls or boulders along the shores of Lake Michigan are about the size of giant beach balls or basketballs and weigh up to 50 pounds.
Click to watch the video from UpNorthLive with Leda.
I looked a little further into the phenomenon and found and AIR PHOTO INTERPRETATION OF GREAT LAKES ICE FEATURES by Ernest W. Marshall in the Great Lakes Digital Library at the University of Michigan. With the help of Marshall’s information, here’s an explanation of how ball ice forms:
Ball ice consists of roughly spherical masses of slush and frazil ice that accrete in turbulent water. Frazil ice (via Wikipedia)is a collection of loose, randomly oriented needle-shaped ice crystals that form in open, turbulent, supercooled water. Lumps that form in the less turbulent zones are typically flattened discs, while those formed in the extremely turbulent zone near the shoreline ice where wave action is strongest form into spheres.
The author explains that ball ice is a feature common to all of the Great Lakes and can occur at any time during the winter where water turbulence breaks up a slush layer. You can read more about this in Great Lakes Ice Features.