29: Frozen Patterns

Nature is full of intricate, precise and beautiful patterns. You only have to look at the perfect hexagons in a beehive or the delicate structure of a spider’s web to see this. These patterns are made by animals, but even the elements have the ability to create some quite beautiful patterns too. This week we will be looking at how water does that, in the form of snow, frost and ice wedges.

Plants leaves leaf macro frost wallpaper | 1920x1200 ...
Frost forming on leaves and branches

Snow flakes

One of the classic winter decorations is a snowflake, and for good reason. They can be really beautiful little things! Snowflakes begin their lives high up in the earth’s atmosphere when a tiny particle of dust or pollen comes into contact with water vapour. The water vapour freezes around it creating a tiny crystal which is now heavier than the surrounding air. As it falls more water freezes onto it from the more humid air closer to earth, causing the crystal to grow. Because of the structure of water molecules, the crystals naturally form into a hexagonal (six-sided) pattern, which is repeated on each side. Whilst they have the same basic structure of six sides, their actual shape varies a lot. As people say, each snowflake is unique which is because of the micro-differences in temperature and humidity they experience whilst falling.

If the weather is cold the snowflakes may clump together to form snow. However if they pass through warmer air as they are falling to earth, they may become sleet or freezing rain as they melt in this warm section of atmosphere.

Photographs of snowflakes taken under a microscope. Each has a hexagonal structure, but their geometry is unique depending on the conditions in the atmosphere as they formed falling towards earth. Picture: NOAA


Snowflakes are usually microscopic, but another larger winter pattern you may have seen with your own eyes is the patterns created by frost on things like windows.

When ice is formed it is often because liquid water has turned into a solid, or gaseous water vapour has turned into a liquid and then a solid. Frost skips out one of these steps jumping straight from a gas into a solid when water vapour in the air comes into contact with a solid surface below freezing temperature. These structures form in a fractal way, meaning their pattern is repeated but smaller and smaller each time. For example if you imagine a tree with 3 branches, and each of those split into 3 smaller branches, and each of those split into 3 more branches etc… that is a fractal structure. This allows the frost to form into tiny rough crystal when it is out in the open air, for example on a leaf or even sometimes the surface of snow.

However, if you have ever seen a badly insulated window in a cold winter, you’ll notice they can have very large patterns. Here the minuscule scratches, bumps and dust on the glass can affect how the ice crystals form. As they are not outside, the frost crystals are forced to form in 2 dimensions instead of 3, pushing them into more elaborate shapes.

File:Frost on the window 03.jpg
Frost that has formed on glass, creating a pattern almost like feather. Picture: Alexandr frolov/Wikimedia Commons/ CC BY-SA 4.0)

Ice wedges and polygons

So far we have covered the microscopic and the just-about-visible scale. What about big stuff though?? This is where ice wedges come in, as they can create patterns on an entire landscape level.

Ice wedges are formed when a little bit of water gets into a dip or crack in the ground. In winter time this freezes, and as ice is bigger than water it pushes the soil out creating a larger crack. In spring more water accumulates here and the next year the ice freezes thicker and deeper, widening the crack even more. Over time this will create a triangular wedge of ice going down into the ground, sometimes many meters deep. As the soil is slowly pushed outwards, it starts to form little ridges on top of the wedge as there is nowhere else for it to go. As these get bigger they create blocky patterns on the landscape called polygons (though they are not exactly the shape of a polygon). These can usually be seen quite clearly, as the soil in the ridges are a lot thicker than the soil on the edges, so different plants live on and around the polygons. The polygon patterns can become quite huge, interlacing with one another to create a tight knit set of shapes on the landscape.

As the polygons get even bigger the middle of them might start to sink (as the soil ridges are at their edge) allowing a little pond or eventually lake to form. These are called thermokarst lakes and can be from tens of centimetres to 1 km in size. When you have many of these it creates an extra pattern of little lakes on the landscape. In summer the spaces between the polygon may be full of water, creating what looks like a network of islands.

Polygons in the landscape formed by ice wedges. Picture: Hannes Grobe/Wikimedia Commons/ CC BY-SA 2.5)

Human Patterns

Perhaps slightly less ‘natural’ but still very beautiful, the Artist Simon Beck has been using snow as his canvas to create some incredible pieces of art. As snow tends to hold its shape when compressed, Simon has been on some long and carefully calculated walks, using his foot imprints to create stunning patterns which you can see below.

Patterns in the snow created by artist Simon Beck

Nature is full of beauty, symmetry, patterns and shapes, whether due to the way water molecules happen to join together, ice crystals grow, or even just the creativity of people to use the landscape around them in a interesting way. Even the coldest, harshest places on earth have their delicate and stunning sides.

For more info:

An article on Simon Beck’s artwork: https://www.theguardian.com/science/alexs-adventures-in-numberland/gallery/2014/nov/06/simon-becks-snow-art-landscapes-mathematical-designs-drawings-alps

An explanation of how ice polygons form with pictures, in case my description was a bit confusing: https://www.fws.gov/refuge/arctic/permcycle.html

Music: kongano.com

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