Tuesday, December 16, 2008

Frost flowers

This is about something magical, something that I've never seen before.

While we read with concern about the ice storms and terrible weather in the Maritime Provinces and the northeastern U.S., here in Colorado we love the snow we received and we're enjoying our -20 degF (-29 degC) nights and our -5 degF (-20 degC) days. Truly.

Of course, we dress like polar explorers before we go outside to enjoy the weather.

The last couple of nights I've donned my polar-explorer garb, taken the dog out for his evening constitutional, and found something new and wonderful in the frosty night.

Scattered on the sidewalk were what looked like little blossoms of frost, about the size and shape of clover blossoms. They caught the light from the street lamps and sparkled in the dark. I stopped to get a closer look at them.

Each frost flower, or frost blossom, grew where there was some snow, or a light coating of frost, on the sidewalk. It appeared that the blossom needed the water molecules already on the ground to grow, because I didn't see any blossoms growing on bare concrete or asphalt. And each blossom needed a nucleation site, a place to start growing. Any bump or protrusion on the sidewalk would do, even a pebble of snow or ice left by the shoveling crew. The blossoms grew not from water freezing out of the air, but from water molecules migrating through the snow and ice into the crystal structure.

Wherever there was a supply of ice, and a place to start growing, a blossom would begin to take shape. First one petal would start, no bigger than a pencil eraser, but then quickly growing to the size of a quarter (or a euro or a loony) and looking, on close examination, like an arm of a snowflake. If the dog was patient enough, I could squat under a street lamp and watch the petal grow, the dendrites on the edge adding to themselves, lengthening and forming branches before my eyes. Eventually another petal would start, and then another, until the flower was fully formed, each petal like part of a giant snowflake, reflecting the light from the street lamp in a different direction.

The frost flowers covered the sidewalk like wildflowers in a mountain meadow. I didn't want to tread on them, for fear of breaking them and destroying the magic. I'll try to get pictures of them tonight and post them here.

UPDATE, DEC 17: Unfortunately, the warm weather (20 degrees above zero instead of 20 below) has returned, and the frost blossoms have disappeared. The next time they appear, I'll go home and get the camera for sure.


Sarah Elkins said...

It is amazinf what you can see if you take time to look! I would love to see pictures, good luck taking some!

Susan said...

My friend forwarded this website to me. It's cool, you should check it out. http://www.newscientist.com/gallery/dn16170-snowflakes/5. (I'm trying to make a link, but my html memory is short. If it doesn't work, oh well.)