Shot at about the same time as Monday's post. Cold river and ice flowing downstream on the Mississippi, the weird stuff that comes out of the Missouri River shaped like discs. There was a terrific comment to that post explaining how these things form:
Often, when pondering the amazing amount of ice flowing down the Missouri River at times like these, folks will ask, "I wonder where that ice comes from?", usually imagining that it's being created in a certain place or kind of place then drifts down the river.Time for a few days out of the cold. Mrs. C and I are meeting up with U "R" Us in Las Vegas tonight and then heading out in the morning to Death Valley. We go there every few years for its wild, remote beauty. It's just 2 hours drive from Las Vegas and there's a very comfortable central village, Furnace Creek. Many pix sure to follow.
From what I gather, most of it is created everywhere in the river. Most of the ice is called frazil (or frazzle) ice. It is formed when small, needle-like ice crystals actually form in or on surface of the water as turbulence in the river causes some of the water to become supercooled, or just below freezing. These then begin to stick together, creating a slush. The current gathers the slush together and the frazil begins to freeze to each other. The tumbling action of the current and of slush blocks hitting each other and rolling off the banks and each other causes these circle "pancake ice" or "frazil pan" to form.
On very cold days, near zero, frazil sculptures can build up on the pans. As pans bump into each other, they may tilt up, then freeze to another pan, creating some of the towering iceberg structures.
On the Missouri, one of the most interesting things to me is how the ice appears white, despite the turbidity of the water.
Another ice formation you might see are large sheets of ice that break out of tributaries or in the eddies along the side of the river. If there is frozen border ice along the river and the river drops or rises dramatically, these sheets will break loose and go on down the river.
I've seen some as large as a row of barges. Awesome.
Here's a link to some basic river ice facts from the Army Corps of Engineers: http://www.crrel.usace.army.mil/ierd/ice_guide/iceguide.htm