An ice spike is an upward-facing icicle that forms as a body of water freezes. Water expands when it freezes. If there is already a thin sheet of surface ice over the body of water, further freezing can force water out and upwards through a crack or weak point in the sheet. This can produce a tube-like structure where water emerges at the tip, progressively lengthening the tube. Tube formation stops when the tip freezes and seals. The formation of ice spikes is related to the shape of the water body, the concentration of dissolved impurities, air temperature and air circulation above the water. This particularly one was approximately 3" high and had formed in the bird bath.
