Icicle

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An icicle is a piece of ice hanging from a tree or from a roof of a house. They typically have a form of a long cone with vertice pointing downward. Icicles can have caverns inside. Several icicles together often form an irregular shape.

[edit] Formation of icicles

Icicles form when the temperature is below zero degrees Centigrade and when there is a supply of water. Typically, temperature is just a few degrees below zero and water is melted by the Sun, for instance on the roof of a house. Water, under its weight, flows down and freezes, thus increasing icicle's size. If temperature rises, water can no longer freeze, and icicle can even start melting and diminishing in size.

If weight of an icicle exceedes its firmity at the point where it is attached to an object, the icicle breaks and collapses onto the ground.

[edit] Typical problems

Icicles, hanging off the roofs of building, wires etc. can be a serious safety problem. Falling icicles can cause severe injuries to pedestrians and sometimes even cause lethal wounds, especially upon hitting to the head. Weight of icicles can lead wires to break and, rarely, fragile structures to collapse.