The Anatomy of a Snowflake: How Snow is Constructed in the Winter

Winter is finally here as snow falls across the country. And while you may think that all snowflakes are the same, they're not. In fact, each snowflake doesn't just look different, but also has unique characteristics depending on how "wet" they are. Now, we're taking a closer look at the true anatomy of a snowflake.

A snowflake is not one piece of ice. Instead, it's made up of 200 separate ice crystals. This means that the intricacy of each snowflake is far more complex than you might first think.

The ice crystals in snowflakes actually owe their six-fold rotational symmetry to the hydrogen bonds in water molecules. As the water freezes, water molecules bind to other water molecules and form a hexagonal structure; each point on the hexagon is an oxygen atom, and each side of the hexagon is a hydrogen bonded to an oxygen. As freezing continues, more molecules are added to this structure and eventually creates a snowflake.

However, what kind of snowflake is created depends entirely on the weather conditions in which it forms. There are actually 35 distinct categories of snowflakes, and all of them depend on temperature and humidity

For example, the simple prism snowflake, which looks like a simple, icy hexagon, occurs around 28 degrees Fahrenheit and low humidity. The stellar plate, which looks like a hexagon with six more hexagons tacked onto its edges, forms in the same conditions.

In contrast, the stellar dendrite, which is the most common of snowflake shapes and looks a bit like six thin arms with two spikes protruding from each arm, occurs about 10 degrees Fahrenheit with high humidity.

What's interesting is that all of these different types of snow also have different properties. For example, the fernlike stellar dendrite, which looks like the stellar dendrite but with more branches, makes for the best powdered snow and thus the best skiing conditions. The best packing snow, which you use to make snowballs or snowmen, has a relatively high moisture content and a temperature that's right around freezing.

So is each snowflake unique? They all form differently. But they may be far more unique than you first thought.

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