Powder snow is easy to slide on and doesn’t hurt, but is it more dangerous?

Snow is a fascinating natural phenomenon. Whether you are lying by the window watching the regular hexagonal snowflakes falling from the sky, or watching the snow gradually cover the earth with pure white, it is a refreshing thing.

Image source: Photo Network

Powder snow is soft and fine, giving people a unique feeling of floating in the air when skiing. It also does not hurt when you fall, so it is sought after by many ski enthusiasts.
Why is powder snow so magical? Let’s find out today.

01

How is powder snow formed?

Before we talk about powder snow, we have to go back and look at how snowflakes are formed.

First of all, snow is not frozen rain, but when the atmospheric temperature is low enough, water vapor skips the liquid state and condenses directly from gas into solid snow crystals (less than 0.1 mm). When the snow crystals roll in the clouds, the surrounding water vapor continues to condense, making the snow crystals become larger and more complex, until it is too heavy to stay in the air, and becomes a falling snowflake.

Image source: snowcrystals.com

Almost every snowflake is unique. When snow crystals roll and absorb the surrounding water vapor, they do not necessarily accumulate and condense more water molecules horizontally from the "side" as shown in the diagram above. They may also develop vertically and become plate-shaped, column-shaped, needle-shaped, branch-shaped or even barbell-shaped.

Snowflakes of various shapes

Image source: www.its.caltech.edu

The final shape of the snowflakes depends on the meteorological conditions at the time. Different combinations of temperature and humidity will produce different types of snowflakes. Heavier and thicker needle-shaped snow crystals are usually formed when the temperature is between -5℃ and 0℃ and there is a lot of moisture in the air. When the temperature is below -20℃ and there is less moisture in the air, small plate or column-shaped snowflakes are often produced.
The most perfect powder snow flakes are produced between 0℉ and 10℉. Their perfect hexagonal shape and large branch-like branches make the snow flakes tend to overlap lightly rather than being tightly compacted, ensuring that the new snow contains a large amount of air with a density in the range of 30~50kg/m³.

Image source: Reference 1

However, for powder snow to accumulate into a snow track, it is not enough to have perfect snow flakes, wind conditions are also very important. Usually, powder snow is more likely to be seen near the top of the mountain where the wind speed is less than 15 miles per hour. Otherwise, too strong winds will roll up the snow and make them piled tightly together, no longer remaining loose. Ski enthusiasts do not look for powder snow by observing the shape of snow flakes with a magnifying glass, but by a more intuitive indicator: Snow -to-Liquid Ratios . The higher the snow-to-liquid ratio, the lighter the snow, and vice versa.

Snow-to-liquid ratio forecast for ski resorts Source: wric.com

If you take 30cm of new snow and melt it to form 3cm of water, then the snow-to-liquid ratio is 10:1, which means the snow is "heavy". The common snow-to-liquid ratio in most mountain ski resorts is 12:1, so when skiers encounter a piece of powder snow with a snow-to-liquid ratio of 20:1, they will be very excited.

Powder snow is soft and dry, and the snowflakes are not tightly attached to each other so a large amount of air is retained inside (air accounts for 90% of the volume of powder snow). It is extremely smooth to slide on and has a certain elastic support. Falling on it feels like being supported by an air cushion and of course you won’t feel any pain.

Image source: Photo Network

By the way, wet snow, which is the counterpart of powder snow, is not completely useless. Although it is wet and heavy , it requires more energy to slide and it is more painful to fall on it. But the property of wet snow that it easily sticks to each other makes it a perfect material for rolling snowballs and making snowmen.

Is powder snow dangerous?

However, the perfection of powder snow hides dangers. On December 23, 2023, a Chinese female tourist died of suffocation after inhaling powder snow after falling while skiing in Niigata Prefecture, Japan.

Image source: Guangming.com Because the powder snow is very soft, it feels like there is an air cushion to support you when you fall.

It is painful, but it can easily make people sink very deep into the water, making it difficult to climb out on their own. It can also easily enter the mouth and nose when the skater falls, leading to passive inhalation and suffocation.

There is another more common risk: loose snow can form tree wells several feet deep at the edge of a tree trunk. 70% of snow immersion suffocation incidents are caused by tree wells. The loose snow in the snow pit is like quicksand, and the body's gravity continues to pull people down until the loose powder snow covers the nose and mouth. If the angle between the skier and the ground is greater than 30 degrees when the skier falls, it is almost impossible to climb out by himself. If there is no companion to help from the outside, it will become very dangerous within a few minutes, just like drowning.

Image source: Reference 3 03

How to enjoy skiing safely?

As an extreme sport, skiing has many potential risks, from falls, frostbite to avalanches, which can cause minor or serious injuries to participants.

The following rules can help us minimize the risks of skiing to a certain extent:

Understand the conditions of the ski resort, remember the distribution of facilities and warning signs ; comply with the opening hours of cableways and ski slopes and other safety management regulations.

Before skiing, check whether the equipment is safe and reliable, wear protective gear, choose a safe route , and do not cross the boundaries of the ski resort without permission.

Do it within your ability, control your speed and direction , and control the intensity of the exercise. Leave space when sliding down to avoid affecting others.

Learn basic first aid measures ahead of time.

Travel with companions, maintain auditory and visual contact with each other, and have fixed meeting points on the descent route.

If you fall toward a tree, grab onto branches or the trunk to prevent yourself from falling into the well. Do not struggle, try to stay in fresh air, and wait for help from your companions.

References

[1] Kenneth Libbrecht, Rachel Wing, Capturing Snowflakes: Winter's Frozen Artistry, Voyageur Press 2021.

[2] Kenneth Libbrecht, The Secret Life of a Snowflake: An Up-Close Look at the Art and Science of Snowflakes, Voyageur Press 2010.

[3] Baugher P, Area CM S. Snow immersion suffocation-The silent killer at ski areas[C]//Proceedings, 2012 International Snow Science Workshop Anchorage, AK, USA. 2012: 220-226.

Author: Wan San, a former quarantine dog trainer and a classical music blogger who wants to fly a plane

Editor: One person

Acknowledgements: Dai Jianhua, Chief Engineer of Shanghai Meteorological Observatory, provided scientific guidance for this article