Lime Hollow Nature Center
Covered Bridge at the Lime Hollow Visitor Center

From My Sit Spot

by Pete Angie

Snow and IceUnder a few inches of snow, the landscape is utterly transformed from brown and gray to stunning white. Snow and ice are the defining substances of Northern winter, and their arrival is exhilarating, though not without some drawbacks. Melting snow wets the knees of my jeans and chills my legs while I sit nestled in the branches of a fallen maple, listening to the gurgle of the creek and looking for whatever the woods may offer an observer. Eventually I examine a handful of the ubiquitous white stuff that has now stuck to my gloves. Their black fabric makes it easy to see the details of the snow flakes in my hand. Wind, the weight of other snow, and evaporation has degraded their structure, yet a variety of features remain of when the crystals first fell from the sky. If you have not done so already, look closely at a snow flake when it lands on your coat sleeve; use a magnifying glass. Or examine freshly fallen flakes on the top of a window feeder from inside. Often what you will behold is delicate, intricate complexity.

The factors that make snow flakes astounding are elemental. Simply put, snow flakes are ice crystals, and form in similar ways to ice on the surfaces of lakes or creeks. I leave my tree branch nest and lay on my belly beside the nearby creek. The water is mostly covered with opaque ice that looks like a woven fabric, but is smooth like glass. Tapping it, I find it is wine-glass-thin and shatters, revealing another layer of ice an inch below. The multiple layers, I speculate, are the result of changes in water level, brought about by a recent storm. Between the two sheets a lattice of sharp crystals reaches up and down from both surfaces. At the edges of open patches in the ice, where swift water can still be seen, similar crystals reach out from all sides, as though trying to connect. It is this impulse to connect which makes creek ice, and snow flakes, possible.

Positively charged on one end, and negatively on the other, water molecules naturally and easily stick together. Granted, with enough heat energy to make them vibrate fast enough, water molecules will spring into the air as water vapor—this happens all the time, and at any temperature above freezing, from the surface of our skin to the laundry on the line—but water molecules inevitably can't escape the social nature of their charge. Hence condensation and the water cycle, which brings vapor back to Earth as liquid. In the creek or in a glass, they slide about each other in constant motion as that substance we all know and utterly depend upon. And as winter comes on and the air becomes colder, water molecules, like everything else, move less and become more dense. That is until their temperature reaches 39 degrees Fahrenheit, at which point water reverses course and becomes less and less dense, until it freezes at 32 degrees. That is unlike anything else. The shift has to do with how water molecules bond with one another, the form they take when they slow down enough—are cold enough—so that the majority of them are arranged in the same way, creating structures that incorporate lots of gaps and are less dense. The exact mechanics of what happens to water in that seven degree window is beyond the scope of this essay, but it is what sets up water to become ice, on a creek, or in the sky.

At 32 degrees, water is ready to become ice and just needs a nudge. The nudge usually comes in the form of a tiny speck of debris in the lake, or a mote of dust or soot in the air, or even other ice. With something to form on, the reaction that solidifies water into hexagonal ice crystals takes off, even pulling water vapor directly into solid form. A shard of airborne pollen from a tree outside of St. Paul may have served as nuclei and birth point to one of the flakes stuck to my gloves. With the pollen cold enough, water vapor froze directly to it and that ice drew more vapor from the cloud and the sky as it fell. Influenced by humidity, temperature, nature of the nuclei, position in the cloud, speed of the wind, and other factors, the new snow flake perhaps became an intricate, repeating pattern of delicate ice that could put holiday greeting card art to shame. A variation of the same freezing process made the crystals between the two layers of ice on my creek, the layers themselves, and the spiny fingers of ice reaching out into the air to close the gaps above the open water.

Ice and snow can give one a lot of material to think about: such as how melting glaciers provide water for a full sixth of the Earth's population, and how air bubbles trapped in ice can tell us the composition of the atmosphere far in the past. One could wonder if life would have even evolved if water didn't expand at 39 degrees, and ice sank instead of floated. The question I'm stuck on, however, as I rise and pat the snow off my clothing, is: if a bonfire is lit outside of Columbus, or a grandfather shakes out a rug on his porch, will there be a snowday in Cortland? Maybe so.

References:

Gosnell, M. 2005. Ice: The Nature, the History, and the Uses of an Astonishing Substance. New York. Alfred A. Knopf.

Wick, W. 1997. A Drop of Water. New York. Scholastic Press.