Q: Are all snowflakes really individual? Why are they sometimes different shapes?
Well, we're told in kindergarten when making paper snowflakes with safety scissors that every snowflake is the same. But, as it turns out because of the way snowflakes form in the atmosphere, they might actually all be special after all.
“For some time there was some debate about that, but there’s actually been some fairly recent research that suggests, yes indeed, it’s likely that all snowflakes are very unique,” said J. Marshall Shepherd, director of atmospheric science and the Georgia Athletic Association’s professor of geography. “There’s probably not two identical snowflakes that we could find.”
Shepherd said there were about three steps involved in forming a snowflake that made each one particular. The first step involves water vapor condensing on a speck of dust or clay — called an ice seed or ice nuclei — in the atmosphere. The crystalline structures of the minerals help snowflakes take their shapes. The second factor involves the temperature.
“If the cloud’s between about 27 and 32 degrees, the crystals take the form of the six-sided plate that people often see,” he said. “If it’s colder than that, the snowflakes form as little needles. If it’s colder than that yet, they start to form into something called columns or fern-like stars.”
Shepherd said their shape can also be affected by their descent from the clouds.
“As they start to fall some of these snowflakes or crystals can collide with other snow crystals or sometimes they can collide with water in the cloud that hasn’t frozen yet and so they then take on other shapes of their own,” he said. “Sometimes as they’re falling some of the crystal breaks apart and splinters. You can see all of these reasons conspire to make an individual snowflake very unique.”
Shepherd also pointed out that most precipitation starts out as snow or ice just about anywhere that’s not in the tropics.
“Most of our rain, even in the summertime, starts out as snow,” he said. “The rain that falls, even if it’s 80 degrees in the middle of August, it forms as snow but as it falls out of the clouds the temperature is above freezing and so it melts.”