Hair Ice/Frost Beard

Documentarian Ken Burns called the National Parks “America’s Best Idea.” The splendor conserved within the boundaries of the park system features some of the planet’s greatest scenery. The humans who serve within the National Park Service also deserve plaudits. They oversee the pragmatics of the units and contain a wealth of knowledge to share with visitors. The NPS and its constituent parks have increasingly upped their game in a modern arena: social media. Nature lovers can do few things to enrich their online lives more than follow the slew of official accounts associated with the National Parks. They document interesting topics unique to their domains, replete with gorgeous photography and video footage. Katmai National Park’s online presence brings us Fat Bear Week, a new countrywide institution. Subscribers to Mt. Rainier National Park’s online account were recently treated to a relatively rare phenomenon.

Let me introduce you to hair ice:

Hair ice in Mt. Rainier National Park - photo by C. Vecchio

Mt. Rainier National Park and its 14,417-foot volcano are no strangers to snow and ice, but, even in this winter wonderland, one must become lucky to encounter hair ice.

Also known as frost beard (great name) and ice wool, this form of frozen water requires a stringent string of ingredients to form. Temperatures must be within a specific range. The ambient temperature must fall below 0°C (32°F) for ice to materialize, but, for hair ice, the temperature must not fall more than a few degrees below this point. The air needs to be humid. Further, the phenomenon requires a fallen log of a broadleaf tree; this log must be damp and/or rotting. Even if all the above conditions occur, the ice requires a location on the log to be barkless, open to its innards. Frost beard grows on sections of wood called medullary rays, or vascular rays. These structures grow perpendicular to a tree’s rings, stretching radially from the cores like capillaries. If all the above ingredients are present but the tree’s location on the planet did not rest between 45 degrees north latitude and 55 degrees north latitude, sorry, no ice wool.

To top it all off, this hoary happening transpires only in the presence of Exidiopsis effusa, a fungus from the family Auriculariaceae. Frost beard gives a whole new meaning of hair growing from fungus!

Not an Appalachian Trail blaze but Exidiopsis effusa - photo by Jerzy Opiola
The band between 45 degrees and 55 degrees north latitude

The physical attributes of hair ice might be as odd as the formation requirements.

Each filament is extraordinarily fine, measuring just 0.02 millimeters (0.0008 inches) in width. The length, by contrast, can extend as long as 20 centimeters (8 inches)! This combination makes the strand frangible, but, like real hair, it can become curly or wavy. If conditions are right, the beards can retain length or swirly shapes for an extended period, illustrating another odd attribute of the ice. Normally, small instances of ice undergo a process called recrystallization, during which the small particles become larger ice crystals spontaneously, sort of like ice cannibalism in reverse. For some reason, this frozen water resists forming larger crystals.

Hair ice can be quite stunning visually:

There's a small piece of wood under that beard - photo by Vielfalt
Hair, beard, or wool? - photo by Paca68420
Upper and lower beard - photo by TOMMES-WIKI

Perhaps the first known human to catalog a sighting of hair ice was Alfred Wegener in 1918. Students of deep science trivia might recognize the name: half a decade prior, he had discovered continental drift, the basis for modern plate tectonics. This dude was a veritable geo-Nostradamus. He not only nailed the moving continents, but he predicted a fungus would be the culprit behind hair ice.

His notion could not be marked completely correct until 2015, when German and Swiss scientists unlocked the secret behind Exidiopsis effusa. Though the exact method of the fungus’ manipulation of water remains a mystery, they demonstrated the species lived in every instance of frost beard. Further, killing the fungus killed the process. The scientists hypothesize that the fungus imparts some sort of antifreeze protein, which has been shown to disable recrystallization in other forms of ice.

Alfred Wegener, purveyor of continental drift and hair ice - unknown photographer

At The Mountains Are Calling Headquarters, we’re about five degrees too far south to hit the winter forests in search of frost beard. Readers in the extreme northern portions of the United States, southern Canada, and the middle swaths of Europe and Asia might just stumble on porcelain hair sprouting from dead wood. Well worth a waltz through chilly forests!

Further Reading and Exploration

Hair Ice – Mount Rainier National Park Official Facebook Page

Hair Ice – Met Office/National Meteorological Service of UK

Evidence for biological shaping of hair ice – Biogeosciences

Fungus shapes hair ice – Researchers identify fungus responsible for peculiar ice filaments that grow on dead wood – European Geosciences Union

Solving the mystery of ‘hair ice’ – Science Magazine

Recrystallization of Ice – Encyclopedia of Snow, Ice and Glaciers

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