IMAGE Frost Flowers, Union Wood, Sligo, 10 Dec 2012

Claudia Florchinger captured these images of one of the most rarest ice formations, "frost flowers" or "feather frost", in Union Wood, County Sligo, today.

Frost flowers usually grows on a piece of water-logged wood (twig/branch), as shown in Claudia's the pictures. A typical example looks like a small puff-ball of cotton candy, a few inches across, made up of clusters of thin, curved ice filaments.

Not much has been written on this unusual phenomenon. It appears that the ice filaments are essentially pushed out from pores in the wood as they freeze. It's something of a misnomer to call this frost, by the way, since it freezes from liquid water, not water vapor.