Mist is tiny droplets of water hanging in the air. These droplets form when warmer water in the air is rapidly cooled, causing it to change from invisible gas to tiny visible water droplets.

Mist often forms when warmer air over water suddenly encounters the cooler surface of land. However, mist can also form when warm air from land suddenly encounters cooler air over the ocean. This is the cause of the summer fog in San Francisco, California. You can even create mist yourself, as you probably know, when you exhale the warm air from your body into the cold air.

Mist is a lot like its cousin, fog. The difference between the two depends on how well you can see. Mist is less dense than fog. If you can't see beyond one kilometer (two-thirds of a mile) in front of you, it's fog that's clouding your vision. If you can see more than that, it's just mist.

Mist caused by volcanic activity is simply hot water vapor expelled along with gases and, sometimes, lava, by a volcano. Volcanic mists are emitted by steam vents, or cracks in the Earth's surface around volcanoes and geysers. Sometimes, volcanic mists are watery clouds you can walk through. Steam vents are popular tourist attractions at Volcanoes National Park in the U.S. state of Hawaii, for example.

Sometimes, however, these volcanic mists have other chemicals in them, often causing distinct odors. Volcanologists study the chemical properties of these mists to see what rocks and gases are under the volcano. They also measure the temperature. The hotter the steam, the more likely the volcano is to erupt. A difference of only a few degrees can mean the difference between a nice mist and a steam explosion.

You'll find mist all over the world. Some of the world's most famous foggy spots, such as Scotland, in the United Kingdom, are also home to mist. Scotch mist, in fact, is a very light, steady drizzle of rain.

mist
Different temperatures cause water vapor to condense and form mist over a lake.

Gorillas in the Mist
Zoologist Dian Fossey studied mountain gorillas and their behavior over 18 years in the African country of Rwanda. Her famous book about the experience is called Gorillas in the Mist.

behavior
Noun

anything an organism does involving action or response to stimulation.

chemical
Noun

molecular properties of a substance.

chemical property
Noun

unique identity of a substance expressed by its type and arrangement of molecules.

Dian Fossey
Noun

(1932-1985) American zoologist.

distinct
Adjective

unique or identifiable.

drizzle
Noun

very light rain.

erupt
Verb

to explode or suddenly eject material.

exhale
Verb

to breathe out.

expel
Verb

to eject or force out.

Noun

clouds at ground level.

gas
Noun

state of matter with no fixed shape that will fill any container uniformly. Gas molecules are in constant, random motion.

Noun

natural hot spring that sometimes erupts with water or steam.

lava
Noun

molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.

Noun

clouds at ground-level, but with greater visibility than fog.

mountain
Noun

landmass that forms as tectonic plates interact with each other.

mountain gorilla
Noun

mammal (primate) native to Africa.

odor
Noun

smell.

rapidly
Adverb

fast.

rock
Noun

natural substance composed of solid mineral matter.

sauna
Noun

room in which steam causes visitors to sweat.

scotch mist
Noun

fog and drizzle.

steam explosion
Noun

violent expansion of liquid water into vapor. Also called a littoral explosion.

steam room
Noun

chamber filled with water vapor, used in spas or parts of saunas.

steam vent
Noun

cracks in the Earth near volcanoes or geysers where water is heated by volcanic activity.

Noun

degree of hotness or coldness measured by a thermometer with a numerical scale.

tiny
Adjective

very small.

vapor
Noun

visible liquid suspended in the air, such as fog.

volcanic
Adjective

having to do with volcanoes.

volcanologist
Noun

scientist who studies volcanoes.

Noun

state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.

zoologist
Noun

person who studies animals.