"Frost is to dew as snowflakes are to raindrops." So says, Cal Tech. They continue, "When frost forms as minute ice crystals covering the ground, we just call it all frost. But sometimes the frost grains grow larger and are called hoarfrost crystals. Good hoarfrost is not that uncommon if you watch for it. . .[It] grows whenever it's cold outside and there is an ample source of water vapor nearby."
Hoarfrost is, I suspect, the frost with which most of us are familiar. In cold country, it is the frost which often accompanies fog. Because fog (summer or winter) is an uncommon visitor to Elk Lake, I could not resist, a few days ago, pulling out the macro lens and trying to capture the intricate ice creations formed by nothing more than water and air!
What follows are photos taken in various locations - all the same day with two different lenses - one a very close up macro with a limited depth of field which I am still learning to use. (NOTE: Just for some perspective - Not one of these 'ice creations' is longer than 2 inches. Many are smaller than a pencil eraser)
Some of the most beautiful hoarfrost examples look very much like what I shared a couple posts back. They were found in a similar location. Nonetheless the weather conditions were totally different. Thus their similarity adds to the intrigue.
To me, the name, "Hoar Frost" conjures up spooky images. In fact, one might guess it originated on some foggy medivial Haloween night. However, the word actually comes from an Old English adjective describing advanced age. It has been applied to the frosty whiteness which clings to trees and bushes since it makes them look like they have grown white hair.
According to Wikipedia, "Hoar Frost may have different names depending on where it forms. For example, air hoar is a deposit of hoar frost on objects above the surface, such as tree branches, plant stems, wires; surface hoar is formed by fernlike ice crystals directly deposited on snow, ice or already frozen surfaces. . ." So, technically all but my last image are examples of air hoar, although the surfaces were already frozen so, maybe, surface hoar? This ice crystal stuff can get confusing!
According to Weather Online "Under clear frosty nights in winter soft ice crystals might form on vegetation or any object that has been chilled below freezing point by radiation cooling. This deposit of ice crystals is known as hoar frost and may sometimes be so thick that it might look like snow. The interlocking ice crystals become attached to branches of trees, leafs, hedgerows, and grass blades and are one of the most prominent features of a typical 'winter wonderland' day. However, the fine 'feathers', 'needles', and 'spines' might also be found on any other object that is exposed to supersaturated air below freezing temperature."
I leave you with one final image. Here is a lovely example of what some might consider corn snow. However, unlike corn snow (which is loaded with moisture and represents snow which has begun to clump together due to melting and refreezing, thus its other name 'spring snow'), this is actually snow covered with Hoar Frost. As you can see, Hoar Frost is not limited to branches and twigs and grasses. It 'grows' on the snow too, as the water vapor moves up through the snow on clear, cold nights. It is extremely visible where the snow has developed 'waves'.
Although I could not capture the effect, it was very interesting to see the ice 'flakes, when shaken gently from the branches and twigs, fall like paper-thin glass mini-plates (about the size of a pencil eraser) onto the snow. It is this phenomenon which, according to Wikipedia, "is a cause of avalanches. . .when buried by subsequent snows." In fact, these fragile ice crystals can actually be maintained even when covered by more layers of snow.
Yes, I admit it, I am fascinated by this 'new look' at an old medium. However, I promise not to dwell on it too much longer :-)
Lady of the Lake