Natural History Moment

Snow in Springtime, February 2006
By Annemarie Goetz, Keystone Science School Program Coordinator

Snow in the Springtime: If you don't like the weather in Colorado, wait 5 minutes. Early spring weather of February, March and April in Summit County can be summed up in one word…change. From the moment water vapor freezes in the atmosphere to the moment it melts as spring runoff, weather is building and changing our snow. With every change in weather we will see the characteristics of snow grains and layers in the snowpack change. This causes changes in the shape and size of individual snow grains as well as the formation of layers within the snowpack. In the world of snow science this change is called snow metamorphosis. (Meta meaning change and Morpho meaning form or shape.)

To explore the process of snow metamorphosis, let's dig down into the snowpack…deeper, all the way to the ground. You may notice it's a little warmer down here. The snow grains are larger and more loosely packed. They have square, rectangular and triangular shapes. You may even notice some striations (stripes) on the hollow grains and their crunchy texture. Due to fluctuations in our daily weather patterns which change the snowpack temperature, snow grains turn from ice into water vapor without ever melting. As water vapor is pulled through the snowpack it "sticks" onto colder snow grains producing beautiful grains called facets. This name comes from their many flat edges, called facets, just like a diamond!

Now dig up into the middle of the snowpack…you may notice the snow getting cooler; it’s a little harder to dig through. The snow grains are smaller and more rounded. You have dug your way into a layer of rounded snow grains. These snow grains form when temperatures within the snowpack are fairly constant, causing a layer of snow to settle and form strong bonds between the snow grains. Due to the strong bonds between rounded snow grains this type of snow will make fabulous snowballs!

Past Natural History Moments

Color change is not just for Aspens, October 2006

Snow In Springtime, February 2006

Aspens in Autumn, October 2005

Let’s dig up to the surface and see what we find…brrrrrrrr! Looks like another very cold night with no wind and clear starlit skies. You might be finding crystals on top of the snowpack that resemble feathers from a bird’s wing. On very clear nights, the atmosphere pushes air down on the snowpack. When water vapor in this air touches the cold surface of the frozen snowpack, it will "stick" to the snow and form surface hoar. Similar to facets at the bottom of the snowpack, the water vapor near the surface changes directly into ice. Surface hoar can be blown away by a small breeze or the breath from your lungs. If you find it in the early morning still in shade, you can watch the surface hoar crumble before your eyes as the first rays of sunlight touch them.

Now go ahead and dig through the snow and see what you can find!