ice crystal
Quick Summary
An ice crystal is the solid form of water, typically hexagonal in shape, that forms from water vapor in the atmosphere. These crystals are fundamental to the formation of snow and other precipitation.123
Formation and Structure
Ice crystals form through vapor growth, where water molecules attach to a surface in a nonequilibrium state called supersaturation. The specific shape and size of an ice crystal depend on the temperature and the amount of water vapor available during its formation. Common shapes include plates, columns, needles, and dendrites.41
Role in Precipitation
In clouds, ice crystals grow by accumulating water vapor or by colliding with supercooled water droplets, which freeze upon contact. As these ice particles grow and become heavy enough, they fall from the clouds. If temperatures are cold enough, they reach the ground as snow. If they melt during their descent, they become raindrops.14
Ask Britannica AI about this topic
Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.