Dec 09

Rime Ice

by Michael Rosekrans, Naturalist

As the days shorten and grow colder, Yellowstone begins to brace for winter. Natural processes unseen to the common visitor occur, transforming this dynamic ecosystem from a boisterous, bustling place of bugling elk to a seemingly frozen world sleeping underneath a blanket of snow. With close observation, those fortunate enough to spend winters here can see that every day the world of Yellowstone is still very much alive and in constant flux.

A fresh blanket of snow or a morning so cold you can see a bison’s breath suspended in mid-air is no doubt aesthetically pleasing. But in all that bison breath and in all that porous space between layers of snow pack are processes metamorphosing our most precious resource from a flowing agent of life to unimaginable frozen shapes and formations one might see in a fantasy movie.

When ski pioneer Billy Hofer came through during the harsh winter of 1886 he exclaimed, “I was startled by the resemblances to men and animals the ice-laden trees showed, as, standing sentinel duty on each side of the road, they appeared to be watching our approach. Everything was loaded down with the steam frozen as it had drifted from the geysers. There were fantastic forms of men and women looking into the pools…animals of all kinds and shapes, creatures that outside of the Park nothing but a disordered mind could conjure up.” Hofer was seeing our famous lodgepole pines covered in a phenomenon known as rime ice.

Rime ice forms as wind carries supercooled cloud droplets that freeze upon impact with the cold surfaces of our lodgepole pine needles. Astoundingly intricate formations take shape on the branches of the trees. These ice formations that are so unique to Yellowstone are thanks to our hot and steamy thermal areas becoming supercooled in our winter atmosphere. If you happen to be visiting the park on a chilly winter morning, stop as you pass by one of our geyser basins and let your imagination take control. See what icy images your mind conjures up from our frozen forests.


This article was originally published in the Winter 2019 issue of Yellowstone Quarterly.