Click on image for full size
Snow is part of the cryosphere. It is a type of precipitation in which water falls as ice crystals, or combinations of many ice crystals, called snowflakes. Snowflakes form in clouds where the temperature is below freezing (0ºC, or 32ºF). The ice crystals form around tiny bits of dirt that have been carried up into the atmosphere by the wind. As the snow crystals grow, they become heavier and fall toward Earth.
Each snowflake can be made of as many as 200 ice crystals. Many snowflakes are symmetrical hexagonal (six-sided) shapes because water molecules often organize with this type of symmetry as they freeze. If they spin like tops as they fall to the ground, they may be perfectly symmetrical. Other types of snowflakes end up lopsided. Different types of snowflakes form in different conditions. Temperature determines if the crystals become a flat plate, a long column, or a prism shape.
On average, 10 inches of snow melt down to about an inch of water; however, not all snow is the same. Some places receive very heavy snow. For instance, only five and a half inches of January snow on Mount Washington, New Hampshire, melt down to an inch of water. In contrast, over 15 inches of January snow at Crested Butte, Colorado, melt down to an inch of water.
There are areas on Earth where snow covers the land surface year-round. These areas are often known as snowfields and are found both at high latitudes, where snow is common and temperatures stay cold year-round, and on mountaintops, where the high altitude causes temperatures to be cold year-round. The extent of the snow cover can change with the seasons - more snow added during winter and some of it melted away during summer. Recently, the snow cover on some mountaintops, especially mountains at low latitudes, has been shrinking because the Earth is getting warmer.
Last modified January 29, 2007 by Lisa Gardiner.
Shop Windows to the Universe Science Store!
The Summer 2010 issue of The Earth Scientist
, available in our online store
, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.
You might also be interested in:
Frozen water is found in many different places on Earth. Snow blankets the ground at mid and high latitudes during winter. Sea ice and icebergs float in the chilly waters of polar oceans. Ice shelves fringe...more
Even though most snowflakes have a hexagonal structure, there are many ways that water molecules can arrange themselves as the water freezes. Some people say that there are no two snowflakes alike. However,...more
A flash of light was seen in the night sky over Greenland on December 9th. It is thought that a meteor may have plunged through the atmosphere and landed on the southern part of the island. It was said...more
Scientists are learning about how dust from wind storms is affecting the snow pack in Colorado. When the winds are right and the desert is dry, dust blows to the east from U.S. Southwest. When this happens,...more
Altostratus belong to the Middle Cloud group (2000-7000m up). An altostratus cloud usually covers the whole sky and has a gray or blue-gray appearance. The sun or moon may shine through an altostratus...more
Cirrostratus clouds belong to the High Cloud (5000-13000m) group. They are sheetlike thin clouds that usually cover the entire sky. The sun or moon can shine through cirrostratus clouds . Sometimes, the...more
Cumulonimbus clouds belong to the Clouds with Vertical Growth group. They are generally known as thunderstorm clouds. A cumulonimbus cloud can grow up to 10km high. At this height, high winds will flatten...more