What Causes Icicles?

Water dripping from any surface can initiate icicle formation and in the dead of winter, snow is often the primary source of water. The combination of below freezing air temperature and heating from the sun can melt snow and as the melt water begins dripping from a rock or other surface, the competition between gravity pulling the water downward and surface tension holding water molecules together, leads to the formation of evenly-spaced ripples along the flow front. These ripples will freeze when and where the surface temperature dips below 32 degrees Fahrenheit with the frozen ripples becoming the icicle roots. Icicles then grow as water dripping over the roots freezes in progressive layers.

New icicles are typically cone-shaped with air bubbles and various material embedded within the ice. Icicles grow downward and outward simultaneously but at differing rates and as they grow, vertical ridges and horizontal ribs, or rings, form on their outer surface.

Today's photo was taken last month along the trail to Fallingwater in Bear Run.

Reference:   Spectrum Educational Enterprises

"Silent icicles,
Quietly shining to the quiet moon. "
                       -- Samuel Taylor Coleridge (from his poem "Frost at Midnight" published 1798)

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