Please explain: full birdbath collapsing into slush?

Factual Questions
1

This mystified me and I wonder if someone can explain it.

We have a small birdbath, about 20" in diameter and about 4" deep in the center. It had been raining all morning and the birdbath was full to overflowing. About 3:00 pm it started to snow and shortly thereafter (maybe 30 minutes) I looked out at the birdbath and the entire contents had collapsed into slush. About half of the volume was missing and the level of the slush was way below the rim.

I don’t understand where all of the water went. If it had solidified into ice, it would have been an ice cube roughly the same size as the water. I can’t think of any mechanism that would turn the water into slush and reduce the volume so much.

Can anyone explain this?

Thanks,
J.

2

Since you weren’t watching the entire time, someone could have tipped it over.

3

A recent freeze could have cracked it, and water leaked away.
An animal could have drank from it.
An animal could have splashed in it.

4

Thanks for the reply. It isn’t cracked. It’s still holding water. We would have noticed an animal large enough to drink from it, or an animal splashing in it enough to empty more than half of the water. Likewise, nobody tipped it.

J.

5

If there was enough wind to cause the snow to accumulate on one side of the birdbath, I can imagine once it bridges with the snow accumulating of the surace of the water, the porous texture of the snow would let it work like a wicking siphon to draw the water out and down the outer wall of the birdbath.

You can probably recreate the phenomenon by wetting a length of paper towers and spreading one end on the surface of the water, and draping the rest against the outside of the birdbath (make sure it clings to the wall) to a point below the bowl. It won’t be as dramatic as an actual siphon, but the wide and shallow shape of the birdbath should make the water easier to wick away.

6

Hmm, this is an interesting idea. There WAS some wind. Not a whole lot, but perhaps it was enough…

J.

7

This makes sense … although I think the cause would be capillary action … the liquid water is drawn up into the ice lattice … transverses across the lip of the [del]cat feeder[/del] bird bath … and then trickles down the side …

Easy to demonstrate on the kitchen counter … fill a cup with water and drape a paper towel over the rim so one side is immersed in the water and the other hangs outside the cup … put it in your sink and wait overnight …

Wind may not be required … the snow may have have a clingy nature allowing enough of an overhang to get the wicking process moving …

8

Are your trees snow covered like ours are now? We have big clods of snow falling off them. If one landed in your bird bath it’d both explain how it’s slushy and where the water went - just got splashed out when the clod landed.

9

The snow will only last when the wind is really cold… like at freezing or just above.

So first the bath is full. Ice forms right at the top.

Now snow builds up on the ice, and the weight of the snow displaces water from under the ice, which goes out over the edge.
As the snow melts, a lot of the melt goes over the edge.
Well anyway I think the net result is that the bath filled up with snow which displaced the water … pushed it over the edge. When the snow melted, it had half the volume.