Backyard Biology

Nature stories from my backyard and beyond

Nature Stories

Snowflake Science

Thursday, February 3, 2011

It is snowing outside. The first real snowfall of the year. The large white snowflakes fall gently to the ground, landing with an almost audible hiss. Each flake is lost among the millions that surround it, yet we can imagine in our mind each individual snowflake as it falls, a delicate perfectly formed six-sided crystal.
We all know what snowflakes look like. Many of us has spent many happy childhood hours cutting out their patterns in white paper. Yet most people have never really observed them up close. A few minutes doing this every snowfall is well worth the effort.
Snowflakes are very easy to collect and observe. All that is needed is a piece of black felt and a magnifying glass. During a snow fall, let a few crystals land on the felt and look at them with the magnifying glass. But you must be careful not to breath on them. The warmth from your breath will cause them to melt and disapear as you are looking at them. What you see may astound you!

The first thing you may notice is that snowflakes come in a variety of patterns. In 1951, the International Commission on Snow and Ice defined seven different patterns of snowflakes (correct terminology defines a single unit of snow as a snow crystal. A snowflake is more than one crystal or pieces of crystals joined together. However, since most people are familiar with the term snowflake, I will continue to call all snow crystals snowflakes). The patterns are: star, plate, needle, column, column with a cap at each end, spacial dendrite and irregular.
Many snowflakes did not fit easily into this classification, so a couple of snow researchers created another classification that contained one hundred and one different patterns of snowflakes!
It is not necessary that snowflake observers recognise all one hundred and one patterns in the snowflake classification. In fact, it is much more fun to make up your own classification system for the snowflakes you collect.
Over the course of the winter, you should be able to collect many different types of snowflakes. If you record what you find, you could soon begin to produce your own classification system. You should also record the temperature and humidity that the snowflake formed in. You will notice that a particular pattern of snowflake will almost always be formed under similar conditions.

As you observe your snowflakes, you may be surprised to see that very rarely will you find a perfect six-sided snowflake. A snowflake starts its life as a tiny ice crystal that forms around a particle of dust or sea salt high in the clouds. If there is enough water vapor in the cloud, the crystal continues to grow. When it has grown to a certain size, it begins to fall.
Depending on the conditions in the cloud, the snowflake may continue to grow during its descent, it may stop growing or it may stop and start again several times. If the snowflake passes through supercooled water vapor - water that remains liquid at below freezing temperatures - it will collect a coating of rime. This rime remains liquid until it touches something - like the ground. Then it instantly freezes around the snowflake.
On its descent through the cloud, the snowflake may collide with other snowflakes and break apart. Each part may continue to grow on its own as it passes through the cloud. Or two flakes may become joined when they collide. An updraft may push the snowflake back up into the cloud where it will start its journey again. With all of these possibilities, it is not surprising that a perfect six- sided snowflake is not all that common

It is said that no two snowflakes are exactly alike. And while you may never collect two snow crystalsidentical snowflakes, chances are many snowflakes have identical twins. It has been estimated that it takes 1 million snowflakes to cover an area 2 foot square and 10 inches deep. Now consider that about 3/4 of the earth is snowed upon and that this has been happening for billions of years. Chances are very likely that, somewhere, at sometime, an individual snowflake has had a twin.

Snowflakes are one of natures most beautiful creations. A little time spent collecting them can brighten up any stormy winter day. If you `would like to learn more, I recommend you read, “Field Guide to Snow Crystals” by Edward LaChapelle.