How does a volcano fume?

Answer 1

A fumarole is the name given to a gas emitting vent in a volcanic area. These are generally not direct emanations from the volcano itself (but may be) the result of evaporating ground water by heat from the volcano. The water may originate deep within the earth and may carry with it quite noxious materials such as fluorine, and chlorine. But the supply of water could be from the sea itself. The steam may be very hot and even glow at night. This phenomena is at the higher end of the hot springs regime, and many fumaroles are essentially permanent.

Often a long term fumarole will be surrounded by a sinter cone of ejaculate.

In Alaska, a 1912 eruption covered an area of about 100 km2 with volcanic ash and for a long time, the whole valley had tens of thousands of fumaroles as ground water was evaporated. The Valley of Ten Thousand Smokes was the name given to it at the time. As it has cooled, most of the fumaroles have proved to be temporary.

In addition to the small-scale features above, a volcano which has an active lava lake will emit fuming. Mt Erebus in the Antarctic is a well known example. Close to an eruptive phase, the Hawiian volcanoes also emit much gas from the lava lake.