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Why does fog form over volcanoes?


There could be a couple of reasons that you see fog or clouds above volcanoes.

Many active volcanoes are still emitting gases, which contain water vapor. At the height of the top of te volcano, it is often quite cold, so the water vapor condenses into fog or cloud (fog is really just a cloud near the ground).

Another possibility is that air is being lifted over the volcano; the air has to go somewhere, so when the wind blows air towards the volcano, the air has to either go around the volcano or rise above the volcano. Air cools as it rises and if it cools enough to bring the water vapor in the air to the condensation point, a cloud will form over and/or around the top of the volcano.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory

The "fog" you see above volcanoes is a mixture of smoke and hot steam that has condensed in the cooler atmosphere. The steam comes from water from deep within the Earth.

Vince Calder

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