Snowflakes: How do they grow?
How are snowflakes formed?
Several things need to happen in order for snow to form. First, there needs to be moisture in the air. Second, the temperature needs to be low enough for ice crystals to freeze. Third, there needs to be a tiny piece of dust or other particle for the crystals to form around. These particles are usually carried into the atmosphere by the wind.
The moisture needed to make snow comes from lots of different places. The main source is evaporation. Evaporation is how water is turned into vapor and transfered from the earth’s surface to the atmosphere. Most of the vapor comes from the oceans. Lakes, streams, plants and animals also produce water vapor.
As water vapor rises into the atmosphere it cools down. If it gets cold enough, the vapor will begin to condense. When this happens close to the ground we get dew and fog.
Higher in the atmosphere the vapor will condense on tiny particles, forming a cloud. As the vapor continues to condense, it eventually gets heavy enough that it will fall. In the summer it falls as rain, if it’s cold enough, it turns to snow.
Too Cold To Snow?
Maybe you’ve heard people say “it’s too cold to snow.” Although it seems to snow less when it’s really cold, it’s never really too cold to snow. It snows on the South Pole where temperatures are colder than 40 below zero.
The reason it doesn’t usually snow when temperatures are below zero is because when air starts to cool, it starts producing snow. By the time it gets really cold, the snow has already fallen and there’s no more left in the super cold air.
There are three factors that influence how much evaporation takes place, they are:
Wind - The stronger the wind, the more evaporation takes place.
Temperature - More evaporation takes place at higher temperatures.
Humidity - Humidity is the measurement of how much moisture is in the air.
Just like a sponge, air can only hold so much water before it falls out. The drier the sponge, the more water it will absorb. The same is true with air.
Is it true that no two snowflakes are alike?
To answer that question, we need to understand how snowflake shape is determined.
First, vapor condenses around a particle.
Then it grows into a hexagon (six sided shape.)
As the crystal grows it will form arms on each corner of the hexagon.
As the crystal moves through different temperature and humidity, new plates will grow on the end of each arm. Since conditions are the same across the small crystal, the budding ams and plates will usually grow to the same size and shape, making the snowflake symmetrical.
As it continues to move, getting blown around inside the cloud, new arms will grow on the corners of the new plates. Each time the snowflake moves through a new temperature or humidity layer new plates and arms form. Since no two snowflakes will go through the exact same layers, they will each form different plates and arms. Since no two paths are the same, the chances are that no two snowflakes will be exactly the same.
Activity: Grow your own crystals
Since this activity requires the use of hot water, it should only be done under adult supervision.
- Boil some water and carefully pour it into a glass jar.
- Add a couple of spoons of salt and stir until it dissolves. Continue adding salt a little at a time until it no longer dissolves.
- Tie a piece of string to a pencil and tie a paper clip to the other end. Make the string long enough to almost reach the bottom of the jar.
- Place the pencil across the top of the jar so the string hangs down into the salt solution.
- Leave the jar undisturbed overnight. Within 24 hours you’ll see crystals start to grow on the string.
- For a little variety, add some food coloring to the water and you can grow different colored crystals.
Activity: Catch a falling star
Snowflakes aren’t really stars, but their hexagonal shape and unique form make them fun and interesting to look at. If you live in an area that gets snowfall, take some time to go outside during the next storm and catch a few flakes.
If you have a dark coat you can let the snowflakes land on your sleeve. A dark piece of paper also works well. Most snowflakes are very small, smaller than Abraham Lincoln’s head on a penny, so you might need a magnifying glass to see what they really look like.
Dreaming of a white Christmas?
What makes snow white? Snow is made up of ice crystals. Even though these crystals are really clear like glass. When a whole bunch of them get together they look white.
The colors we see are really light rays reflected by the surface we are looking at. Each ice crystal in the snow reflects different colors, but since there are so many of them, they appear to be reflecting all the colors.
When all the different light colors are reflected we see it as white. Since snow crystals reflect almost all the light, it appears to be white. When there is no light reflected our eyes see black.
Ice crystals absorb small amounts of red light. This means that they reflect more blue than red. That’s why sometimes snow appears to have a slight bluish color.
Skiing is big business and since nature doesn’t always make snow when skiers want it, we have learned how to make artificial snow.
Snow machines mix water and compressed air and shoot them out of nozzles.
The fine droplets of water freeze as the air decompresses. A big fan is used to blow the ice particles onto the slopes.
Artificial snow is made of frozen water droplets and doesn’t have the flake or crystal-like shape of real snow.
Activity: Make your own snowflakes
Making your own snowflakes out of paper can be fun and easy. All you need are some scissors and lightweight paper. White paper looks most like real snow, but any color will work.
Fold the paper as shown in the diagram and start cutting out irregular shapes along the folded edges. When you’re finished cutting, unfold the paper to reveal your own homemade snowflake.
You might be surprised at how your snowflake looks. They can be very simple or quite complex. Remember, no two snowflakes are exactly alike, so there’s no right or wrong way to make your snowflake.
A Word Of Caution
Because snow reflects light so well, there are some inherent dangers to keep in mind when spending time outdoors on sunny winter days.
It’s easy to get sunburned, so you should apply sunscreen before going outside.
The bright light can cause snow blindness, basically sunburned eyes. To prevent this, always wear sunglasses on bright winter days.