appear when water vapor condenses directly into ice. A snowflake describes a
single snow crystal or a group of snow crystals. The foundation of a snowflake
begins with a water droplet. Water droplets in clouds are unique in that they
do not freeze immediately when the temperature decreases below zero degrees
Celsius. Alternatively, they stay in their liquid form in a supercooled state.
At negative forty degrees Celsius pure water droplets will freeze. Water
droplets with dust, on the other hand, start freezing at a much higher
temperature of negative six degrees Celsius because the dust allows for a solid
surface to begin the freezing process. Individual frozen droplets will grow as
the water vapor condenses onto the surface, solidifying into a crystal-lattice
structure. When the snow crystal accumulates enough weight, gravity will pull
There is truth
when people say that no two snowflakes look alike. Each snowflake has a unique
shape and pattern. To start, the angles between atoms in a water molecule
create a hexagon shaped ice lattice, causing six-fold symmetry. Shapes of
snowflakes can range from thin hexagonal columns to slender hexagonal plates.
One example of a particular shape of snowflake is bullet rosettes, named for
its bullet shaped columns. Star-shaped or stellar snow crystals are another
shape. These snow crystals have six primary branches which are embellished with
ridges or patterns. These could have additional side branches that would be separated
by multiples of sixty degrees and run parallel to their adjacent rows of branches.
One special shape of snowflakes is called capped columns. These are created when
a snow crystal begins to form as a column and changes to forming into a plate growth.
The shape of a snowflake emerges with time as water vapor condenses to the crystal
surface. The lattice structure helps to explain the six-fold symmetry, but fails
to explain the complex shapes of snowflakes. The crystal shape formed is dependent
on the temperature and humidity of the surroundings. At negative two degrees Celsius
thin plate-like crystals appear. At negative five degrees Celsius slender needles
form. At negative fifteen degrees Celsius large, thin plate-like crystals develop.
At negative twenty-five degrees Celsius and below the crystals grew as short columns.