Physics Question #1866

Bobby, a 12 year old male from Oak Ridge asks on January 24, 2004,

I would like to know what causes inverted icicles. I have a photo I've just taken if you need to see it. Our puppy's water bowl outdoors has had several inverted icicles recently and I cant seem to find anything about them online.

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The answer

Barry Shell answered on January 26, 2004

I did a quick google search at on "ice stalagmites" and found a lot about this. There are many theories and much speculation but the one that seems the most likely has something to do with the mechanics of crystallization of water as it turns to ice. Apparently this phenomenon only happens in plastic containers. Details here:

Trevor Hopkins of England answered on February 14, 2012

 I took photos today of an inverted icicle that appeared in frozen water in an upturned plastic chair.  Your description of its cause being a process of crystallization in a plastic container therefore makes good sense. It was certainly a weird thing to see.
Ice stalagmite

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