How does snow form?

Photo via Snowflakes Bentley (Wilson A. Bentley)

From The Cortez Journal (Gabi Morey and Kristie Borchers):

What is snow, anyway? Snow crystals are born in high-altitude clouds, thousands of feet above Earth. Clouds are made up of water vapor containing microscopic water droplets. Clouds are visible because a million trillion water droplets are collected in one area. At the very center of the water droplet is a tiny particle of dust or salt. With below-freezing temperatures, the water droplets become very complex snow crystals.

How do snowflakes form?

  • Dust (sometimes salt) acts as a nucleus for condensation.
  • Water vapor condenses on the dust.
  • The water droplet grows larger in size.
  • When water cools, it freezes and becomes an ice crystal.
  • The crystal grows six-sides.
  • The crystal becomes heavier as more water vapor condenses and it begins to fall.
  • The crystal’s shape continuously changes as it falls and experiences continued condensation.
  • The crystals fall out of the clouds into warmer air, which makes them bunch-up together into snow
  • No two snowflakes are alike! Scientists have studied the growth of crystals in high-altitude clouds. In 1988, one scientist accidentally found twins in samples of ice crystals. While not identical, snow scholars called these two ice crystals “very much alike.” In the 20 minutes that it takes a typical ice crystal to fall to earth, two crystals would have to be exposed to identical conditions of temperature, pressure and moisture content. All collisions – and subsequent formations – with other crystals would also have to be identical, which makes identical snowflakes virtually impossible.

    Snow is part of something called the cryosphere. The cryosphere includes the parts of the earth that are frozen in snow or ice. This includes the Antarctic, Arctic, sea ice, glaciers, as well as places such as mountain tops full of snow and ice, and even frozen soil.

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