Snow

Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground. It is frozen water throughout its life cycle, starting when ice crystals form in the atmosphere, grow to millimeter size, and then fall to the surface where they may change over time.

Snowstorms develop by feeding on atmospheric moisture and cold air. Snowflakes form around tiny particles in the air, attracting supercooled water droplets that freeze into hexagonal crystals. These crystals can take many shapes, such as platelets, needles, or columns. As snow builds up into a snowpack, it can blow into drifts and change over time through processes like sintering, sublimation, and freeze-thaw.

Major snow-prone areas include the polar regions, the northernmost half of the Northern Hemisphere, and mountainous regions worldwide. In the Southern Hemisphere, snow is mainly found in mountainous areas and Antarctica.

Snow influences many human activities, such as transportation, requiring roads, airplane wings, and windows to be cleared. It also supports agriculture by providing water for crops and protecting livestock. Additionally, snow is essential for sports like skiing, snowboarding, and snowmachine travel. It also plays a role in ecosystems by insulating plants and animals during winter.

Precipitation

Snow develops in clouds that are part of larger weather systems. Snow crystals grow from tiny droplets of water that freeze in cold air, forming different shapes based on temperature and moisture. These crystals fall to the ground as snow.

Snow clouds often form in low-pressure areas, where warm and cold air meet. They can also form near large bodies of water, like lakes, when cold air moves over warmer water, picking up moisture and creating snow on the downwind shore. Mountains can also create snow when moist air is forced upward, cooling and forming snow as it descends on the other side.

Accumulation

Snow builds up from many snow events in places that stay cold enough, like the Arctic, Antarctic, and high mountain areas. We can measure how much snow has fallen using special tools that melt the snow and count the water it makes.

Different kinds of snow events exist, from light flurries to big blizzards. A blizzard is a severe snowstorm with strong winds and low visibility. Snow can fall in different amounts, and scientists measure new snow with a board to keep track of how much falls each day.

Some places get a lot of snow. For example, a mountain in the United States once got over 28 feet of snow in a season, and a town in Japan gets around 57 feet of snow each year on average. The biggest snowflake ever recorded was about 15 inches across!

Metamorphism

Snow changes shape and texture from the moment it lands on the ground until it melts or turns into glacier ice. It starts as light, powdery snow and gradually becomes denser and more granular. This happens because the snow is pressed down by its own weight, blown by the wind, and goes through cycles of melting and refreezing. Water vapor can also add tiny ice crystals, called hoar frost, when the weather is very cold and still.

Over time, snow can either melt away or turn into a type of snow known as firn, which is on its way to becoming glacier ice. In colder climates, snow may stay on the ground all winter. By spring, it usually becomes about half as dense as water. If it lasts into summer, it changes into névé, a type of granular snow that has partly melted, refrozen, and compacted.

Main article: Firn

Movement

Snow can move in several ways after it lands on the ground. One way is through drifting, where wind pushes loose snow into piles that can be several meters deep. This drifted snow can sometimes turn into a dangerous avalanche on steep slopes. An avalanche is a fast-moving slide of snow down a hill. There are different types of avalanches, including slab avalanches, which happen when a layer of snow breaks off, and powder snow avalanches, which can travel very quickly and cover long distances.

Another way snow moves is through melting. In spring, snow often melts and feeds rivers, especially in mountainous areas. This melting can cause rivers to flood during certain times of the year. Over many years, snow can also turn into glaciers. When snow piles up in special bowl-shaped areas called cirques, it compresses into ice and slowly moves downhill due to gravity.

Main article: Avalanche

Main article: Glacier

Science

Scientists study snow in many ways. They look at how snow forms, how it changes over time, and how it affects rivers and the environment. They use different tools to measure snow, such as satellites and ground observations. Their work helps engineers build better vehicles for snowy places and helps farmers understand how snow affects water supplies.

Snow scientists also classify snow based on its properties, like how dense it is or how it looks under a microscope. They measure things like how much area is covered in snow and how deep the snow is. Satellites help them watch snow from space, and these observations show that snow cover has been changing over time in many parts of the world. These changes are linked to climate change, which can cause snow to melt earlier or cover less area.

Effects on civilization

Snow influences many parts of our lives, especially transportation, farming, buildings, and fun winter activities. It can make it harder to travel by car, train, or plane, but it also helps farms by providing water when it melts. Buildings need to be strong enough to hold up snow, and people enjoy many sports like skiing and snowboarding in the snow.

When snow falls, it can slow down cars on roads, trains on tracks, and planes on runways. Roads often use special tires and chemicals to keep traffic moving, while airports use brushes and snowplows to clear runways. Trains use snowplows to clear tracks and sometimes special structures to keep snow from covering the tracks. Farmers sometimes use fences to guide snow into places where it can melt and provide water for crops later on.

Snow is also important for farming because it acts like a blanket, keeping the ground warm and protecting plants from very cold temperatures. When the snow melts in spring, it provides water that helps crops grow. Many rivers get a lot of their water from melting snow, which is important for irrigation.

Buildings must be built to handle the weight of snow on their roofs. Engineers use special rules to make sure roofs and power lines can support snow without breaking. In winter, people enjoy many activities in the snow, such as skiing, snowboarding, and snowmobiling. Ski resorts often make their own snow to keep slopes covered longer.

Snow can also affect wars and military operations. It can make it hard to see targets or move around, but it can also hide soldiers and make it harder for enemies to attack. Historical battles, like those in World War II, show how snow and cold weather have influenced military strategies and outcomes.

Main article: Winter sport

Main article: Cold-weather warfare

See also: Ski warfare

Effects on plants and animals

Plants and animals that live in areas with lots of snow have special ways to survive. Plants can protect themselves by going dormant or storing energy in seeds. Animals might hibernate, stay warm by clustering together, or make special chemicals to stay unfrozen.

Snow can change how plants grow and where they live. Trees, especially conifers, can catch snow in their branches, which changes how much snow stays on the ground. Snow can help plants by storing water, but plants need the snow to melt before they can start growing again. Sometimes, melting snow can wash away plants, changing the land.

Many small animals live in or under the snow. Insects like spiders, wasps, beetles, snow scorpionflies, and springtails can stay active even when it’s very cold. Some small warm-blooded animals, like voles and pikas, store food under the snow to eat later. Larger animals like wolves, coyotes, foxes, lynx, and weasels search the snow for these smaller animals.

Outside of Earth

Snow isn't just something we see on Earth! Other places in our Solar System have their own versions of snow. On Mars, there is water-based snow that falls at high latitudes, and carbon dioxide snow that adds to the planet's icy poles during winter. On Venus, a metallic substance similar to snow covers the tops of its highest mountains.

On Saturn's moon, Titan, scientists have found signs of methane snow, and on Pluto, methane frost falls from high altitudes. These different kinds of snow show how snow can form in many places beyond our planet!