By now, most areas of the Northern half of the United States have seen quite a bit of snow. You may have noticed, though, that all that snow does not look alike. We have often heard that no two snowflakes are alike. While that has some truth to it, there are indeed similar types of snow. According to one study, there are 121 types of them. Before we examine them, a bit of background information on snow might help.
A snowflake begins to form when an extremely cold water droplet freezes onto a pollen or dust particle in the sky. This creates an ice crystal. As the ice crystal falls to the ground, water vapor freezes onto the primary crystal, building new crystals – the six arms of the snowflake.
That’s the short answer.
The more complex explanation is this:
These ice crystals that make up snowflakes are symmetrical (or patterned) because they reflect the internal order of the crystal’s water molecules as they arrange themselves in predetermined spaces (known as “crystallization”) to form a six-sided snowflake.
Ultimately, it is the temperature at which a crystal forms — and to a lesser extent the humidity of the air — that determines the basic shape of the ice crystal. Thus, we see long needle-like crystals at 23 degrees F and very flat plate-like crystals at 5 degrees F.
The intricate shape of a single arm of the snowflake is determined by the atmospheric conditions experienced by the entire ice crystal as it falls. A crystal might begin to grow arms in one manner, and then minutes or even seconds later, slight changes in the surrounding temperature or humidity causes the crystal to grow in another way. Although the six-sided shape is always maintained, the ice crystal (and its six arms) may branch off in new directions. Because each arm experiences the same atmospheric conditions, the arms look identical.
No two snowflakes look alike because individual snowflakes all follow slightly different paths from the sky to the ground —and thus encounter slightly different atmospheric conditions along the way. Therefore, they all tend to look unique, resembling everything from prisms and needles to the familiar lacy pattern.
Types of Snowflakes
This brings us back to the different types of snowflakes. In a 2013 study, A global classification of snow crystals by K Kikuchi & others, the authors described 121 types of snowflakes. This latest study splits the classification into 39 intermediate categories, which themselves can be grouped into 8 general categories. Each of the intermediate categories have specific characteristics, which are detailed at length in the research paper.
If this isn’t enough for you, here is the graphic showing all 121 types of snowflakes.
The next time it snows, take a closer look at those flakes. With your newly acquired knowledge of snowflake formation conditions, you may be able to identify the types of snowflakes that are falling.