Leaf Litter, A Monochrome Study

Day 56: One definition of "hoarfrost" is "a crystalline deposit of frozen water vapor formed on vegetation and other objects at temperatures below the freezing point." It has been particularly lush during our recent cold snap here in the damp Pacific Northwest. It can take a number of different forms from fine needles to crystals resembling those of sugar "rock candy." It differs from "frost" only semantically; the term "hoar-" is appended when the crystals become more distinct than a thin film of ice. On the other hand, "depth hoar" occurs at the base of snowpack, building on existing snow crystals and frequently attaining much larger dimensions than "surface hoar." The word "hoar" derives from an Old English term meaning gray or old.

Hoar

Day 48: It's hard to unlearn something when that "knowledge" is deeply ingrained. What I have always referred to as "rime" has been hoarfrost in 95% of all cases, the exception being some of the formations I've seen on wintry alpine mountaintops. What's the difference? Well, here's your chance to join me in practicing my motto: learn something new every day.

True rime is the product of a freezing fog. Hoarfrost is the deposition of ice crystals formed from moisture in the air and occurs in the absence of fog. Rime accumulates when water droplets come into contact with a cold surface. It generally grows toward the prevailing wind. Hoarfrost forms when there is no wind. That said, the literary convention of using "rime" to represent any form of frost is acceptable, but one source says that "compared to rime, hoarfrost forms larger, more delicate crystals, but it is often difficult to tell the two apart; when in doubt 'rime' is never entirely wrong." Still, I'm going to make a point to use the more scientifically accurate semantics from here on out.