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Triangles in a frozen puddle
The tendency of ice to freeze into triangular patterns is a clue to the formation of ice spikes. In a restricted container, the last triangle to close becomes the base for the ice spike which grows up from it.
Ice pressure
During the recent cold spell, we noticed that the pedestal in the centre of our lawn was leaning at a precarious angle. I couldn't think what could have shifted it, though it appeared to have something stuck to its base that was preventing it from standing properly.
The next day, I was trying to make ice spikes and thought I would try a used baked bean can, as the circular shape would prevent expansion sideways and
it has a ridge round the inside at the top which would stop expansion upwards. This might force extra pressure for a spike to form.
It was not a good idea. The water froze first at the top, and the pressure was such that the bottom of the can was pushed out into a convex surface . Needless to say, there was no spike.
Distorted (left) and normal (right) bean cans
I then realised that this was exactly what had happened to our pedestal. We had filled the base with water to make it more stable, and now this has frozen and expanded out at the bottom in the same way as the bean can.
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