Earth Notes: The Sound of Snow

Dec 20, 2017

Waking on winter solstice to a hushed world of bright light, we look outside and see fresh-fallen snow. 

Credit Michael Collier

The fluffy new snow is full of air pockets that absorb sound. But that quiet doesn’t last long. The snow starts to collapse gently under its own weight—and those air pockets and their sound-muffling properties are soon gone. As snow ages, it often develops a smooth, reflective surface and the sound changes—it travels farther and seems clearer.

The sound snow makes when you step on it changes too. In the freshly fallen dry snow of the Southwest, loose-touching flakes make a soft "whoof" with footfall. But as it gets colder, snowflakes compact and come into contact with each other—tiny bonds form between individual snowflakes or aggregates of flakes as they minutely melt and refreeze.

This process, called "sintering," keeps the snow from collapsing more. The resulting structure is like a miniature Rice Krispie treat glued together with sugary marshmallow creme. Except in this case, it’s snowflakes stuck together with frozen water.

As you walk across this icy confection, your footsteps press down and compact the snow until sufficiently solid to support your weight. The bond between flakes is broken, producing a characteristic squeaking sound.

In contrast, water in wetter snow likely lubricates the flakes as your foot applies pressure. With fewer icy bonds to break, you hear a damp, crumpling sound instead of the soft whoosh of perfect powder.