Beautiful to look at, but dangerous to be near It seems everywhere we turn this week, icicles are everywhere. Even homes and buildings which, in “normal” winter months, seem to escape the wrath of the icicle are not immune this season. An icicle is a spike of ice formed when water dripping or falling from an object freezes. Typically, icicles will form when ice or snow is melted by either sunlight or some other heat source (such as heat leaking from the interior of a heated building), and the resulting melted water runs off into an area where the ambient temperature is below the freezing point of water (0C/32F), causing the water to refreeze. Over time continued water runoff will cause the icicle to grow. As water drips onto an icicle and freezes, it releases heat. The warm air rises up the sides of the icicle. That warm air layer acts like a blanket that’s an insulator, and so the blanket is very thin near the tip and thick at the top. That allows the top to grow very slowly and the tip to grow rapidly - creating a long, thin icicle. It’s the same equation scientists use to study stalactites in caves, but instead of water, stalactites are formed by the buildup of calcium left after the water evaporates. Icicles can pose both safety and structural dangers. Icicles that hang from an object may fall and cause injury and/or damage to whomever or whatever is below them. In addition, ice deposits can be heavy. If enough icicles form on an object, the weight of the ice can severely damage the structural integrity of the object and may cause the object to break. Sources: Compilations from www.wikipedia.org and www.sciencedaily.com.