With more than 400 inches of snow annually in Big Sky, Montana, the flakes of snow that fall all around us on a winter day are often overlooked. It’s hard to imagine how many of these little flakes it takes to cover the landscape or provide one of the many powder days on the slopes of Big Sky Resort.
Made up of a number of snow crystals that have bonded together, not all snowflakes are the six-sided, symmetrical image we may have in our heads. Many are actually shaped like needles, columns, or plates. Because so many factors are involved in shaping a snowflake, including temperature, humidity levels, the length of time spent in the air, the melding into other snow crystals, it is impossible for two snowflakes to ever be identical.
A classification system was put in place by the International Commission on Snow and Ice in 1951, designed to help categorize individual snowflakes. Since that time, and as the field of snow science has emerged and evolved, many other researchers have developed their own classification systems. However, the original guidelines are useful for gaining a general understanding of the different types of snowflakes and how their bonding directly affects the type of snow we will ski on during a particular day in Big Sky.
Basic Snowflake Form
Sectored Plates: The plate-like arms of these crystals are divided into sectors. These are thin, flat flakes that come in a variety of shapes.
Stellar Dendrites: Named for their branched form, (dendrite means “tree-like”), these flat crystals usually have six symmetrical main branches and many other side branches.
Spatial Dendrites: These are not flat crystals, but jumbles of many individual ice branches joined together at random.
Capped Columns: These little columns are capped at the top and bottom.
Hollow Columns: Many snowfalls are comprised largely of these hollow, hexagonal columns.
Needles: These crystals are similar to hollow columns, but are more slender and long.
Rimed Crystals: Water droplets that freeze onto a snow crystal are called “rime.” Crystals pick up rime from the water-filled clouds in which they are formed. Some snowflakes are nothing more than balls of rime, which really makes them soft hail.
Irregular Crystals: Some snowflakes get beat up on their journey from turbulent clouds to earth, and arrive broken or otherwise altered. Warm snowfalls are often comprised of the most irregular snowflakes, especially if it is windy.
Other Frozen Precipitation: Aside from snowflakes, many researchers classify three other types of frozen precipitation as graupel, ice pellets, and hail.
Snowflakes and Snow Layers
Together, the different snowflakes form a snowpack, or a layer. Newly fallen snow takes some time to develop into that particular layer, and after each big dump, a new layer is added on to the older ones. The structure of snowpack is a strong indicator of avalanche danger, and the reason many snow experts dig snow pits to determine if there are any weak layers. A weak layer is usually unstable because of a particular type of snow, grain size, or temperature, among other factors. If enough snow is loaded on a weak layer, and other contributing factors in a particular area also add up, such as the steepness of terrain, weather, and the snow load, an avalanche is more likely to occur.
So, the next time you are cruising the slopes of Big Sky Resort, with snow flying overhead, consider the miraculous beauty of these minuscule creations that drop from the sky each winter, and the impact they can have when piled up together.