Icicle

Icicles can form during bright, sunny, but subfreezing weather, when ice or snow melted by sunlight or some other heat source (such as a poorly insulated building), refreezes as it drips off under exposed conditions.

Another set of conditions is during ice storms, when rain falling in air slightly below freezing slowly accumulates as numerous small icicles hanging from twigs, leaves, wires, etc.

Thirdly, icicles can form wherever water seeps out of or drips off vertical surfaces such as road cuts or cliffs.

[3] The growth rate in length typically varies with time, and can in ideal conditions be more than 1 cm (0.39 in) per minute.

These so-called brinicles can kill sea urchins and starfish, which was observed by BBC film crews near Mount Erebus, Antarctica.

Icicles – the "growth rings" or banding on the icicles occurs as the water in the soil above the cliff thaws during the day and freezes during the night.