Saturday, December 15, 2012

The ABC's of ICE

Letters made of ice (c) John Ashley
Words about ice and snow fill libraries. Here's about one snowball's worth.


The compound we call water can change from vapor to ice crystals without first becoming liquid, a process known as, "deposition." (The reverse process, "sublimation," occurs when ice crystals turn to vapor without becoming liquid.)  Snowflakes are composed of ice crystals that form in the clouds, while frost is composed of ice crystals that form on a surface - both via deposition

Ice crystals grow in many distinct patterns, from simple, hollow columns to complex, fern-like steller dendrites. Most ice crystals are six-sided. Triangular crystals are the second-most common, and the rare ice crystal can have up to 12 sides.

The formation of snow depends on air temperature in the clouds, not near the ground. But the heaviest snowfalls typically occur when it is relatively warm near the ground (around 15°F) simply because warm air holds more moisture than cold air. While it can be too dry to snow, it cannot be too cold to snow.

Technically speaking, snow is a mineral. Uncompacted fresh snow is 90-95% trapped air. The amount of water in most fresh snow varies between 4% and 10%, which means that 10" of fresh snow would melt down to as little as 0.4" or as much as 1" of liquid water.

The oldest ice discovered to date is approximately 750,000 years old and located in the headquarters building at Glacier National Park. Just kidding. Sort of. Actually, the oldest ice found to date was in Antarctica.


The ice crystals in snowflakes seem to have captivated our imagination forever. The first written description of tiny six-sided ice crystals was published in a Chinese book, "Disconnection," in the year BC 135.  Some well-known deep-thinkers who were captivated to the point of studying ice crystals included the Bavarian bishop Albertus Magnus (1250), German mathematician Johannes Kepler (1611), French philosopher René  Descartes (1637), English architect Robert Hooke (1665), Japanese painter Shiba Kōkan (1796), and British physicist John Tyndall (1872).

Wilson "Snowflake" Bentley (1865-1931)
In January of 1885, an American farmer by the name of Wilson Bentley was the first person to successfully photograph individual ice crystals, by painstakingly experimenting with and adapting a bellows camera and microscope. He photographed more than 5,000 ice crystals during his lifetime, and published a book-catalogue in 1931 with the clever title, "Snow Crystals."

Starting with Bentley's book-catelogue, Japanese nuclear physicist Ukichiro Nakaya further classified ice crystals and divided them into 41 different types. Nakaya also created the first artificial ice crystal in 1936. His classification was later expanded by two Japanese meteorologists in 1966 to include 80 different types of ice crystals - our current number.

A new kind of crystal made its first appearance in 1878, when the first snowglobe-like object was displayed at the Paris World Fair. Two years later, Austrian Erwin Perzy patented his "Glass Globe With Snow Effect," starting a business that his grandson continues to this day, still working in the same Vienna building where his grandfather had worked. 


About 12% of the Earth's land surface is currently covered with permanent snow and ice fields. On a local scale, the most snow ever recorded in a single storm was 15.75' at Mt Shasta Ski Bowl, in California, between 13-19 February 1959. The most snow ever recorded in a 24-hr period was 63" at Georgetown, Colorado, on December 4, 1913.  I have also read that a single snowstorm can drop 40 million tons of snow, but I can't find any verification of that calculation.

Montana runs wide and deep, so there is considerable variation in the annual average snowfall (from NOAA National Climatic Data). The snowiest Montana town is Cooke City with an average of 201 inches, and the least likely town to find a snowman is Glendive, with an average of 20 inches of snow per year. Other towns averages in descending order: West Glacier 117", Bozeman 91", Great Falls 63", Butte 62", Kalispell 56", Billings 55", Helena 38", Missoula 38".

On the related subject of air temperature, the official low record was -128.6°F on July 21, 1983, in Antarctica. But Montana bears the distinction of having the record low temp in the lower 48 states. On January 20, 1954, it was a brisk -69.7°F at Rogers Pass, near Helena. Montana also holds the record for greatest temperature range ever recorded in one 24-hour period. On January 23-24, 1916, the air temperature in Browning fell from 44°F to -56°F, a difference of 100°F.

Finally, the major Inuit ("Eskimo") languages each contain only a dozen or so root words for snow, about the same as English. Usually around this time of year you might hear that "Eskimos" have over 400 names for different kinds of snow. But that is one of those urban legends that just won't melt and go away.

Letters made of ice (c) John Ashley

All about snow (National Snow and Ice Data Center)
Snowflakes under an electron microscope (pictures)
Field guide to snowflakes  (book)