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Name: William M.
Status: Other
Grade: N/A
Location: MT
Country: United States
Date: December 2006

Although I am from Georgia, I have recently bought a house on the Madison River in Montana. The lore out here and retold by many is that the Madison River is one of three rivers in the world that freezes from the bottom up. This river does gorge when the ice piles up downstream and then backs up but I have a hard time believing or even understanding that this river --or any river--- can freeze from the bottom up. Knowing the density of water as a liquid and as ice, it seems impossible. Can you explain or demyth this?

I agree with you for several reasons: 1. The density difference, as you pointed out. 2. If any body of water froze from the bottom up, after a Montana cold spell in your case, all the fish would end up flapping around on the surface -- a phenomenon that would certainly not escape international recognition. I do not usually like to mention specific books that are in "popular circulation" lest someone think I might profit from doing so, but I will make an exception here (I am not making any money off this!!). There is a captivating book entitled, simply enough, "ICE" by Mariana Gosnell that discusses ice in most of its technical and non-technical aspects. She addresses the ramifications of what would happen if the density of ice exceeded water in equilibrium with it. The "fish thing" is just one of the more graphic.

Vince Calder


The river does not really freeze from the bottom up. Like many rivers, frazil ice (small shards of ice or "crystallized" snow) can actually sink from the river surface into the river water, even down to the river bed forming piles of anchor ice on the river bed.

When the Spring breakup occurs (or sometimes even before) this frazil ice breaks off in small chunks and floats down river immersed in the water. It gets caught on obstacles under the water surface and piles up under the surface ice sheet. In this way it, and the anchor ice on the river bed, may appear to have formed on the riverbed, but that is not actually the case.

This build up of frazil ice as well as the surface ice causes the horrific ice jams in the Spring. I hope that your home on the Madison is well above the river level, as the ice jams on the Madison have often caused floods several feet above normal river level.

There is an informative presentation at

that talks about frazil ice and ice jams.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory

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