The snow crunches underfoot due to the compression of the ice crystals that make it up. When we walk on it, the pressure applied causes these crystals to move, thus creating this characteristic sound phenomenon.
Snow is made up of small ice crystals assembled together, forming a complex structure filled with air. These crystals, often in the shape of six-branched stars, accumulate in a disordered and fragile manner. This arrangement creates a porous structure, that is, full of voids, somewhat like a solid but light sponge. When you walk on it, this structure easily deforms, even breaking, producing the characteristic crunching sound under your feet. The colder and drier the crystals are, the more rigid their structure, thereby accentuating this typical noise with each step.
When you put your foot on the snow, you exert pressure that slightly crushes the crystals against each other. Under this effect, the crystals break or deform quickly, producing that characteristic cracking sound. The colder and drier the snow, the more each step compresses the snow layer, and the clearer and more distinct the small sound of crispation becomes. In practice, it is this rapid breaking of the crystals under your weight that generates the sound wave you hear as a crunch or crack. This phenomenon becomes even more evident when walking on a layer of freshly fallen snow.
Very cold temperatures make snow crystals stiffer and more brittle. As a result, they crunch louder under your feet when the thermometer drops well below zero. Conversely, when the temperature approaches the melting point (0°C), the crystals become moist and soft: they slide against each other rather than crunching, significantly reducing the noise. Similarly, very dry weather promotes powdery and light snow that crunches loudly, while humid air tends to soften the snow and dampen the crunching sound.
Sublimation is when ice transitions directly from a solid state to vapor, without taking the time to become liquid. When the snow is very cold and dry, this happens quite easily. At that moment, tiny crystals on the surface instantly transform into water vapor under the pressure and friction of our steps. This rapid phenomenon creates cavities and slightly cracks the upper layers, resulting in the famous crunching sound we hear. Sublimation thus enhances the brittle and crispy nature of the cold snow beneath our feet.
Not all snow crunches the same under our feet. Powdery snow, light and fresh, makes a muffled, discreet, and soft sound. It hardly crunches at all, as its crystals, soft and spaced out, dampen the noise when we walk on it.
In contrast, packed or frozen snow often produces a sharp, high-pitched sound that cracks loudly under your steps. The crystals, tight and rigid, break distinctly with each pressure from your feet.
Finally, wet snow, which is starting to melt, gives a dull and heavy sound, somewhat mushy. The presence of water in the crystals limits the sharp crunch, thus muffling the usual crunching sound.
In certain polar regions, the distinctive crunch of very cold snow can help residents or adventurers estimate the temperature approximately, without even needing a thermometer!
Sublimation, the phenomenon by which snow changes directly from a solid to a gaseous state, contributes to altering the structure and rigidity of the crystals, also influencing the sound under your feet.
The lower the outside temperature, the sharper and more pronounced the crunching sound of snow becomes. Indeed, at very low temperatures, the crystals become stiffer and more brittle.
Humidity plays an essential role in the sound produced by the snow under your feet: dry, fresh snow will emit a sharp and clear sound, while wetter snow will produce a duller, muffled sound.
During the night, when the atmosphere becomes generally quieter due to a decrease in surrounding noises, the crunching of our footsteps in the snow seems amplified. This impression arises particularly from the more pronounced sound contrast rather than a real variation in the noise produced by the snow.
Yes, there are several tips to reduce noise. Wearing shoes with softer soles or walking gently can help decrease the pressure applied to the crystals. Moving slowly and choosing lightly compacted snowy surfaces also helps to minimize the crunching sound of footsteps.
Yes, the crunch of snow underfoot varies with temperature. When temperatures are very low (below approximately -10 °C), the snow becomes firmer and produces a particularly high-pitched and clear sound. In contrast, temperatures close to the melting point make the sound softer and muffled.
Not systematically, no. The production of crunching sounds depends notably on the density, temperature, and humidity of the snow. Very wet or melting snow tends to produce little noise, while cold, dry, and powdery snow emits a more audible characteristic crunch.
Fresh snow has a fluffy and airy structure that absorbs sound better, producing a soft and muffled noise. In contrast, old or compacted snow becomes denser and more crystalline, resulting in a more pronounced crunch when walked on.
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