This time of year, I try to get out on my snowshoe trail almost every day. And while the recent outbreaks of mild weather have prompted hoar frost on numerous days this month, what I saw the other morning as I traversed a beaver pond near our house was as spectacular as any scene I’ve ever come across.
The pond, which flooded a previously forested area about ten years ago, is riddled with the bare skeletons of those now-dead trees, mostly balsam fir. Seemingly overnight, those bare trees had regrown their needles, only this time every one was glistening white.
I’ve seen hoar frost far more times than I could ever count, and it’s one of the most spectacular things we see during a typical winter. But never had I seen such a dramatic formation of frost, with each crystal extending like a needle, some fully an inch in length. Stepping out from the woods onto the pond that morning, the scene stopped me dead in my tracks. It was absolutely magical.
And what was perhaps the strangest thing of all, that unusual hoar frost was limited to the pond itself. The hoar frost the rest of the way along my trail was routine in nature, pretty but not jaw-dropping to someone who has lived in Minnesota all my life. It’s like some ice crystal fairy had been at work overnight decorating in preparation for my morning’s stroll.
Of course, it probably wasn’t fairies. There is a naturalist’s explanation for this unusual phenomenon, which isn’t hoar frost at all. According to Wikipedia, this type of formation is known as “soft rime,” and it forms through a process called “deposition.” This happens when water vapor freezes directly into delicate, hair-like crystals on cold surfaces during calm, clear nights. These needles are most likely to form on thinner objects, like bare twigs, which remain in abundance throughout the pond.
While it’s nice to know the scientific explanation, on this particular morning on the beaver pond, I would have been perfectly happy believing it was just magic.