When the world wears white again and everything disappears under a thick blanket of snow that’s when the magic of winter unfolds as nature unveils a world of wonders in letting it snow.
Snow crystals are natural works of art, as fragile as they are ephemeral. Each crystal is unique, and yet all develop in accordance with the same six-fold symmetry.
When it is barely below freezing, the first snow crystals begin to form inside the clouds. Over time they join up to form bigger flakes and once they’re heavy enough, they fall from the clouds – and it snows. Each flake is unique. No two snowflakes are exactly alike.
Unlike raindrops or hailstones, snowflakes fall gently from the sky. Once a snowflake touches water, it immediately melts, releasing the air inside. This creates a high-pitched sound that is unique to each flake and inaudible to the human ear without the assistance of technology. On the descent to the ground some of these fragile structures run into warmer pockets of air and melt, but most of them make it all the way to the ground where they form a blanket that keeps growing thicker.
During particularly frosty nights, a fascinating phenomenon occurs. The moisture in the air freezes and turns into hoarfrost. Overnight the landscape is covered with ice crystals. The result is a winter panorama picture book. Sun and hoarfrost frequently go hand in hand as cloudless winter weather is especially cold. However, hoarfrost doesn’t only accumulate on boughs and branches, but also on the blanket of snow. Its crystals differ considerably from the snow below. Hoarfrost is created at about minus eight degrees Celsius (between 17° – 18° Fahrenheit) or lower and the moisture in the air freezes directly on surfaces. Freezing cold winter nights provide ice.
Electrostatic fields align the water molecules hexagonally and this basic structure holds steady as the water slowly freezes and the snow crystal gradually grows until its finished. Between minus 12 and minus 18 degrees Celsius (10 and 0° Fahrenheit) the classic six-armed snow stars or dendrites appear. It’s the temperature that determines how finely branched they become. Freezing water gives off heat which decreases at higher temperatures and this, in turn, causes additional variations in structure because a bigger surface facilitates a discharge of heat. Consequently, dendrites turn out to be distinctly less branched when they’re created at lower temperatures. So not all snow is alike and at very low temperatures, snow crystals take on the form of little tiles, columns and cylinders.
The ice of the snow crystals is colorless and transparent. At the border surfaces between ice crystals and air, the white sunlight is reflected and scattered and with enough randomly distributed ice crystals scattering light in all directions, the overall color that results are white.
So-called condensation kernels serve as seeds around which droplets form out of the cloud’s mist. Moisture accumulates around minute particles of dust and soot. Such particles also serve as freezing kernels for snow crystals to begin to form when the clouds are cold enough. Then they grow linked together and descend as snowflakes to the earth.
Let it Snow, The Secrets of Nature, Klaus T. Steindl, ©2008.
“He giveth snow like wool: He scattereth the hoarfrost like ashes” (Psalm 147:16). “The Lord says, ‘You are stained red with sin, but I will wash you as clean as snow. Although your stains are deep red, you will be as white as wool’ (Isaiah 1:18).” Steps to Jesus, 46.