雪の結晶の長い旅

A Snowflake’s Tale

Though known as a beautiful winter natural phenomenon, snow actually plays a vital role in Earth’s environment and climate. Each year, approximately one-third of the Earth’s land surface is covered in snow. Snow not only serves as a water resource but also influences the balance of Earth’s climate.

Snow first forms within clouds. In cold, moist air, water vapor freezes around tiny dust particles, creating snowflakes. As the flakes grow, they take on various shapes like plates or needles. However, all snowflakes share a common feature: they are hexagonal.

Snow that falls to the ground does not always retain its original shape. Strong winds can blow snow around, causing the flakes to collide and lose their sharp edges, transforming them into rounded pellets. Additionally, when wind gathers snow in one spot, it can form large snowdrifts.

Furthermore, when snow accumulates on the ground, it forms layers. Each new snowfall adds a layer on top, creating a structure resembling a cake. Over time, temperature changes cause the snow grains to continuously alter their shape.

Occasionally, weak layers can form within the snowpack. If heavy snow accumulates on top of these weak layers, avalanches can occur on slopes. An avalanche is the phenomenon of a large mass of snow sliding down a mountain all at once, posing a significant danger to people and animals.

On the other hand, in regions where snow accumulates over long periods without melting, it gradually compresses and transforms into ice. Initially soft and containing much air, the snow is compacted by its own weight into dense snow called firn. With further compression, it becomes solid ice, forming a glacier.

Thus, snow is born in clouds, falls to the ground, changes form under the influence of wind and temperature, and may ultimately become a glacier. When the ice melts, it returns to water and rises back into the sky as water vapor. Understanding this cycle is crucial for studying changes in Earth’s climate.