## Thursday, January 19, 2017

### An ice circle spins its way downriver

Coming from Africa as I do, I'd never even heard of ice circles until reaching the USA, and I've still never seen one in the flesh.  Nevertheless, this one in Washington state earlier this month certainly looks fascinating.  I'm still trying to work out the energy vectors that produce the spinning motion.

There are more images and video clips of the ice circle on the photographer's blog.  One day, I'd really like to see one of those for real.

Peter

Will said...

Water in channels tends to move faster in the center sections, due to less friction from objects and shallows. That should explain the rotation. An ice plate would end up round by shaving it's edges against other objects as it rotates. Notice the debris buildup along the edges of contact with the rest of the ice.

The various elements needed for the situation to develop probably don't occur often enough to make this very common. I suspect the nominal diameter of the ice plate needed is a component of the width of the water channel.

Old NFO said...

Will is right, and you have 'chunks' hanging down in the current that provide the propulsive moment as the current strikes them.

Mark Matis said...

In Canada, they'd have a keg of Molson's stuck through the ice in the middle of that ice circle, and a bunch of lumberjacks wearing tuques sitting in lawn chairs and finishing off that keg! And every five minutes they'd ring a bell, everyone would jump into the river, swim a lap around the ice circle, then climb back out and scramble for a chair. One of which would have been removed while they were swimming.

THAT is how they play "musical chairs" in Canada, eh?

raven said...

I saw one once in the Androscoggin,in Northern New Hampshire, at a bend of the river. Must have been at least 100ft in diameter. At that place, in summer, there would have been a huge eddy in the water so the ice spinning did not seem so unusual, it was just doing what the water was doing underneath.

Leatherneck said...

So. Do they spin clockwise in the Southern Hemisphere?

el diablo loco poco said...

....Only if they form in the commode. :o

John Cunningham said...

I lived in Alaska for 25 years and I never saw or heard if these.

Sarthurk said...

I have to like leathernecks idea. I was thinking of the toilet bowl effect there myself.