Why avalanches exist
Snow is a little wonder in itself, with a highly complex architecture. Snow crystals form when temperatures drop below -12°C. They form around a nucleus, such as a dust particle. When a snowflake is born, it measures about one tenth of a millimetre. Falling from the sky, the crystal grows into a real snowflake. As far as we know, there are no identical snowflakes. Each flake is individual, and each beautiful in its own way, especially on closer examination. Unfortunately, this beauty is extremely fugacious. Its biggest enemy is not time, but warmth. Temperatures above the melting point cause it to vanish forever.
Snow is chaotic. Sometimes, different layers of snow end up on top of each other. If these layers are incompatible and do not bond, and pressure is applied to the top layer, then the top layer can slide off the underlying one. This happens only on sloping surfaces with enough declination. Such a snow slide in steep terrain we call an avalanche. Judging the snow conditions on a slope correctly is difficult and requires knowledge and experience. Even with that, some risk remains because the snowpack's build-up can change every few metres.