Day 100: Hair ice has been on my mind for the last several days, given recent weather conditions, but I have to admit I wasn't thinking about it when I set out for a short walk in a local county park. I was near the top of the one-mile loop when I spotted the first piece alongside the trail, and my jubilant cry of "Haareis!" must have been rather bewildering to the couple walking their dog the opposite direction. They weren't curious enough to ask as they passed me by, but by then, I had already taken pictures and I doubt that they even looked down to see what had grabbed my attention. A little further on, I spotted another example of this fascinating phenomenon. You see, true haareis (hair ice) forms only in the presence of a specific fungus, Exidiopsis effusa. It occurs on decaying deciduous wood and only under certain conditions. Although the precise mechanism of the fungus' role is not understood, it has been suggested that it may provide a natural antifreeze which stabilizes the formation of ice crystals. It has been noted that the ice "hairs" form at the openings of medullary rays (a cellular structure formed in active cambium, perpendicular to the growth rings of the plant). The "hairs" are also similar in diameter to the medullary rays (roughly 0.02 mm). It should not be confused with ground frost (a type of hoar frost which forms in soil).
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